PHILOPATRY AND POPULATION GENETICS ACROSS SEABIRD TAXA
A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF
HAWAI‘I AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF
MASTER OF SCIENCE
IN
NATURAL RESOURCES AND ENVIRONMENTAL MANAGEMENT
(ECOLOGY, EVOLUTION, AND CONSERVATION BIOLOGY)
MAY 2018
By
Carmen C. Antaky
Thesis Committee:
Melissa Price, Chairperson
Tomoaki Miura
Robert Toonen
Lindsay Young
Keywords: seabirds, dispersal, philopatry, endangered species, population genetics
Copyright 2018 Carmen C. Antaky
All Rights Reserved
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ACKNOWLEDGEMENTS
This thesis, my Master’s work, would not have been possible without the help and
valuable assistance of many others. Firstly, thank you to my advisor Melissa Price for guiding
me through my Master’s degree. Her support has made me a better researcher, scientific writer,
and conservationist. I would like to thank my committee members Rob Toonen, Lindsay Young,
and Tomoaki Miura for their feedback, support, and encouragement. Thank you Lindsay for your
expert advice on all things seabirds and being an incredible role model. Thank you Rob for
welcoming me into your lab and special thanks to Ingrid Knapp for guidance throughout my lab
work. I would like to thank Tobo lab members Emily Conklin, Derek Kraft, Evan Barba, and Zac
Forsman for support with genetic data analysis. I would also like to thank all the members of the
Hawaiʻi Wildlife Ecology Lab, especially to Jeremy Ringma and Kristen Harmon for their
support and friendship.
I would like to thank my major collaborators on my project who supplied samples, a
wealth of information, and for helping me in the field, especially Andre Raine of the Kauaʻi
Endangered Seabird Recovery Project, Nicole Galase at Pōhakuloa Training Area, and Tracy
Anderson at Save Our Shearwaters. Thank you to the British Trust of Ornithology and Bird
Banding Laboratory at USGS for preparing and providing access to seabird banding data.
Funding for this project came from US Fish & Wildlife Service. Thanks also to my funding
sources: Hawaiʻi Audubon Society, Pacific Seabird Group, and of course U.S. Fish and Wildlife
Service. Thank you especially to Beth Flint, Sheldon Plentovich, and Michelle Bogardus at
USFWS for the support.
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Last but not least, thank you to my family and friends for supporting me in every way,
shape, and form. In particular, I dedicate this thesis to my Mom, Dad, and Philip for their
enduring support, patience, and love.
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ABSTRACT
Successful conservation depends on an understanding of dispersal patterns for spatially
complex species. Among seabirds there are opposing pressures to either disperse or return to
natal colonies. We explored philopatry across 36 species, based on banding and census data.
Philopatry correlated with foraging strategy, taxonomy, and region, suggesting that translocation
will be more successful for Procellariiformes, those in tropical regions and with non-central
foraging strategies, as they are more likely to return to translocation sites. Additionally, we
compared genetic diversity between two orders of seabirds with differing philopatry and
explored population genetics of a species in the order Procellariiformes, the Band-rumped Storm
Petrel (BSTP; Oceanodroma castro). Findings indicated no difference in genetic diversity
between orders and high genetic diversity within BSTP. Although this study suggests that BSTP
are not at risk genetically, they remain vulnerable to threats. Management efforts to ensure
successful nesting is crucial to recover the endangered BSTP.
v
TABLE OF CONTENTS
Acknowledgements ...................................................................................................................... ii
Abstract ........................................................................................................................................ iv
List of Tables ................................................................................................................................ v
List of Figures .............................................................................................................................. vi
Introduction .................................................................................................................................. 1
Chapter 1. Dispersal under the seabird paradox: Probability, foraging strategy, or spatial
attributes? ..................................................................................................................................... 3
Abstract ............................................................................................................................. 4
Introduction ........................................................................................................................ 5
Methods .............................................................................................................................. 8
Results .............................................................................................................................. 12
Discussion ........................................................................................................................ 14
Chapter 2. Population genetics of the Band-rumped Storm Petrel (Oceanodroma castro), an
endangered and elusive Hawaiian seabird .............................................................................. 31
Abstract ............................................................................................................................ 32
Introduction ...................................................................................................................... 34
Methods ............................................................................................................................ 36
Results .............................................................................................................................. 41
Discussion ........................................................................................................................ 43
Summary …................................................................................................................................. 57
Appendix 1: List of identified O. castro microsatellites from Hawaiian populations .......... 58
Literature Cited ......................................................................................................................... 63
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LIST OF TABLES
Table
Page
1.1
List of seabird taxa included with colony and species associated attributes …………… 19
1.2
Linear mixed-effects model summary of all seabird taxa ……………………….……… 21
1.3
Linear mixed-effects model summary of seabird taxa in tropical colonies ……..……… 22
1.4
Linear mixed-effects model summary of seabird taxa in temperate colonies …..……… 23
2.1
Population genetic diversity statistics for O. castro in Hawaiian island populations .….. 49
2.2
Comparison of population nucleotide diversity within species in the order
Procellariiformes ……………………………………………………………………………….. 50
2.3
Comparison of population nucleotide diversity within species in the order
Charadriiformes …………........………………………………………………………….…..… 52
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LIST OF FIGURES
Figure
Page
1.1
Graphs of hypotheses of predicted philopatry for seabird taxa ………………..……..… 24
1.2
Map of locations of all seabird colonies surveyed ……………...…………………….… 25
1.3
Phylogenetic tree of all seabird species surveyed …………………...…………..……… 26
1.4
Graph of colony size percentage compared to philopatry for all seabird colonies ……... 27
1.5
Graph of colony size percentage compared to percent philopatry to colonies by taxonomic
seabird order …………………………………………………………………………..… 28
1.6
Graphs of colony size percentage compared to percent philopatry to colonies by region
and foraging strategy ………………………………………………………………….… 29
1.7
Principle component analysis of seabird colonies grouped by order …………………… 30
2.1
Collection sites of O. castro across the main Hawaiian Islands …………………...…… 54
2.3
Global distribution of O. castro populations …………………………….....………...… 55
2.2
Phylogenetic tree of global populations of O. castro ……………...………………...… 56
viii
INTRODUCTION
Knowledge on the dispersal and connectivity of species is a key part of conservation
biology and biogeography. Seabirds, spatially complex taxa, are crippled with one of the highest
ongoing rates of extinction, and many taxa are under federal protection (Spatz et al., 2014).
Nevertheless, seabirds continue to be threatened by commercial fisheries, introduced predators,
habitat loss, light pollution, marine debris, and climate change (Croxall et al., 2012). This thesis
examines behavioral philopatry and genetic diversity within seabird populations, and how this
information can be used to inform best management practices for seabird conservation.
Within long-lived colonial seabird species, there are opposing pressures to either disperse
to new colonies or return to natal colonies. The behavior of returning to the natal breeding site,
natal philopatry, usually guarantees resources and mates but also increases the potential for
inbreeding, competition, and ecological traps. There are two types of philopatry, genetic and
behavioral. Philopatry, as measured by genetic means, is defined as less than one migrant per
generation; anything beyond this indicates dispersal (Spieth, 1974; Lewontin, 1974). Behavioral
philopatry is measured by the number of individuals that return to their natal site to breed
(Weatherhead & Forbes, 1994).
Chapter 1 documents dispersal patterns across 36 different seabird species, based on
long-term banding, along with census data. The goal of this chapter is to identify underlying
mechanisms driving behavioral philopatry with seabirds. Chapter 2 examines the effects of
genetic philopatry between taxonomic seabird orders and within a federally endangered species,
the Band-rumped Storm Petrel (BSTP; Oceanodroma castro). This is the first study to look at the
population genetics of the BSTP across the Hawaiian Islands. The evaluation of genetic structure
1
in the present O. castro colonies in the Hawaiian Islands can help prioritize management efforts
toward strategies that will be successful in increasing population size and conserving the current
genetic diversity.
2
CHAPTER 1
DISPERSAL UNDER THE SEABIRD PARADOX: PROBABILITY, FORAGING
STRATEGY, OR SPATIAL ATTRIBUTES?
3
ABSTRACT
An understanding of natal dispersal in spatially structured populations is necessary for
successful conservation. Within long-lived colonial seabird species, there are competing
pressures to either disperse to novel colonies or return to natal colonies. The behavior of
returning to the natal breeding sire, philopatry, usually guarantees resources and mates but also
increases the potential for inbreeding, competition, and ecological traps. Thus, the high degree of
philopatry among seabird species, coined the seabird paradox, is surprising, given their dispersal
capabilities. We evaluated whether seabirds returned to their natal colony at rates greater than
those predicted by potential dispersal variables including colony demographics, life history, or
geography. We compiled long-term banding and census data from 36 seabird species across 465
colonies. A linear mixed-effects model was employed to determine how dispersal related to
colony demographics wing load, foraging strategy, and spatial variables. Our results suggest that
philopatric rates significantly differ from those expected based on colony size and demographics,
and instead predicted by region, taxonomic order, and foraging strategy. The success of seabird
translocation efforts depends on philopatric rates, as seabirds must return to the colony to benefit
from predator control and habitat restoration. Our study suggests that conservation translocation
programs will be more successful for species in the order Procellariformes, as well as for species
in tropical regions, and those with non-central foraging strategies, as these seabird species will be
more likely to return to translocation sites.
4
INTRODUCTION
Seabirds exhibit high rates of colonial philopatry despite high dispersive potential, a
phenomenon coined “the seabird paradox” (Milot et al., 2008). Within long-lived colonial
species, there are competing pressures to either disperse to a novel colony to breed or return to
the natal colony. Individual colonies are not always discrete populations and dispersal to other
colonies is usually made by young seabirds before breeding for the first time (Schreiber &
Burger, 2002). Advantages of dispersal, recruitment to breed at a new site, include the potential
to minimize inbreeding and competition, but dispersal also comes with a high risk of mortality.
Philopatric behavior, where individuals return and recruit to their natal breeding ground, usually
guarantees resources and mates but also increases the potential for inbreeding, competition, and
ecological traps under climate and land use change. Thus, the high degree of philopatry among
seabird species is surprising, given their dispersal capabilities (Milot et al., 2008; Weimerskirch
et al., 1984; Fisher, 1976; Huyvaert & Anderson, 2004; Frederiksen & Peterson, 1999).
A recent review (Coulson, 2016), suggests that previous estimates of philopatry may be
inflated within seabird species due to the failure to consider factors that may influence
coloniality. Colonial breeding, a complex behavior exhibited by the majority of seabirds, is based
on an evaluation of site-based factors. The “commodity selection” theory (Danchin & Wagner
1997) suggests that colonial animals assess environmental conditions to choose where to breed,
considering environmental conditions such as nesting habitat, shelter, predator avoidance, food,
and mates. Likewise, colonial nesting areas such as steep cliffs or isolated islands may be
selected due to a lack of predators. Hence, when assessing philopatric rates to seabird colonies,
one should consider the quality and condition of the natal colony.
5
Variation in philopatric rates across taxa may also be due to other dispersal-associated
variables (Coulson, 2016). For example, wing morphology, linked to the ability to fly, may
influence bird migration (Berthold, 1996). By comparing body mass over wing surface area, or
wing load, to dispersal distance among species, we can determine what portion of dispersal
within a species is explained by wing load. Additionally, foraging mode, central foraging within
near shore waters versus non-central foraging in pelagic offshore waters, may influence
dispersal. Central-place foragers (i.e. Sterna, Pelecaniformes, Sula, etc.) may have lower rates of
philopatry because they must follow the food immediately around their nesting sites (Jovani et
al., 2016; Elliot et al., 2009; Wakefield et al., 2017). Seabirds that are dietary generalists,
switching from terrestrial to at-sea foraging, feed in areas adjacent to the colony (Isaksson et al.,
2016). In contrast, other seabirds, including Procellarid species, forage hundreds, or even
thousands of kilometers away from their colonies and are thus less dependent upon local food
shifts (Freeman et al., 2010; Young et al., 2009; Froy et al., 2015).
Region, associated with particular environmental conditions, may be correlated with
philopatry due to environmentally-influenced factors. For example, tropical waters generally
have a lower productivity and more patchy distribution of resources than polar or temperate
regions (Weimerskirch, 2007), leading to differences in foraging and breeding behaviors. Lower
resource availability in the tropics lengthens breeding cycles (Reynolds et al., 2014; Nisbet &
Ratcliffe, 2008) and many tropical species also exhibit asynchronous breeding cycles which are
thought to be tied to resource availability. Tropical seabirds forage greater distances than
temperate seabirds, due to lower resource availability (Nelson, 1983). For example,
Procellariiformes that breed in the tropics feed in productive high latitude regions during the
nonbreeding season (Conners et al., 2015). Seabirds breeding in the tropics may even shift
6
foraging activities outside of the breeding season, due to low resource availability, or may shift
their breeding season entirely to track resources (Nelson, 2005). In contrast, temperate seabirds
are synchronous due to the short availability of food for their offspring in the temperate summer.
Temperate seabirds tend to breed within or close to colder, more productive waters and forage
less widely than tropical seabirds (Nelson, 1983).
Inter-colony dispersal rates are likely to be affected by factors of colony demographics
such as colony size, number of colonies, and space between breeding colonies (Lebreton et al.,
1992). We expect a higher probability of dispersal from small to large colonies than from large to
small based on the theory of habitat selection shaped by fitness maximization and thus provides
access to more mates (Serrano et al., 2005). In support of this, single species social attraction
studies and mark-recapture modeling have shown that colony size is a driver in post-fledging
dispersal (Fernández-Chacón et al., 2013; Podolsky & Hess, 1992).
In this study, we determined whether seabirds return to their natal colony at rates greater
than expected based on demographic colony structure and dispersal factors, including distance,
number of colonies, size of each colony, wing load, foraging strategy, taxonomy by order, and
region (temperate, tropical). If rates of observed philopatry within seabirds were proportional to
colony demographics, we expected a linear relationship of philopatry to relative colony size. If
philopatry was consistent with the seabird paradox, we expected consistently high philopatric
rates regardless of relative colony size. In contrast, if natal dispersal were random, we expected
philopatry to average 50 % in respect to relative colony size (Figure 1.1).
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METHODS
Seabird banding and census data
Species were selected based on the availability of data from both long-term census and
banding studies. Data were obtained from comprehensive nesting databases as well as long-term
banding databases. Nesting databases indicating colony size and location included Hawaiian
seabird census data from the Bishop Museum Hawaiʻi Biological Survey (Pyle & Pyle, 2017)
and British Isles seabird census data from the Seabird 2000 colony census (Mitchell et al., 2004).
Banding databases of the associated seabird species were provided by the Bird Banding
Laboratory (BBL) for tropical species within the Hawaiian region and by the British Trust for
Ornithology (BTO) for temperate species in the British Isles. Banding data from BBL was
retrieved May 25th, 2017 (USGS Bird Banding Laboratory, 2017) and banding data from BTO
was retrieved July 25th, 2017. Banding recapture data spanned over a century representing a total
of 36 seabird species from the orders Phaethontiformes, Procellariiformes, Suliformes, and
Charadriiformes, including 19 tropical species and 17 temperate species (Table 1.1) within the
British Isles and the Hawaiian Islands (Figure 1.2).
The BBL and BTO banding data were filtered to include all recapture data from
individual birds that were banded as fledglings, including dead or alive recaptures. We assumed
that if an adult individual was observed at the natal site during the nesting season, it had returned
to breed. For BBL data, at-sea captures and those found outside of the Hawaiian colonies were
excluded from the final dataset. BTO data excluded at sea captures. Natal philopatry for each
species was determined by dividing the number of recaptures at the natal site by the total number
of recaptures for the species. For this study, individuals returning to sites under 20 km from their
8
natal banding location were considered to have returned to the natal site, similar to previous
studies (Coulson, 2016). Seabird colonies with less than five recaptures for a given species were
removed from the final analysis due to small sample sizes.
Spatial data
For this study, the term “colony” varied by study system due to differences in data
collection of colony size. For the tropical seabird dataset, each island was treated as a single
colony. For the temperate seabird dataset, each county was defined as a single colony. Distances
between colonies were found by calculating the Euclidean distance between center GPS points of
the focal colonies (i.e. island or county). Although there was high variability in size of the
colonies in both tropical and temperate datasets, there were no outliers within the colony dataset.
Species characteristics: wing load and foraging strategy data
Wing load and foraging strategy for each species were collected from online databases:
Cornell Lab of Ornithology – Birds of North America, The Cornell Lab - All About Birds,
USFWS Hawaiian Island National Wildlife Refuge – Seabirds, and Wildscreen Arkive – Species
(Poole, 2005; The Cornell Lab, 2017; U.S. Fish & Wildlife Service, 2017; Arkive, 2017). Noncentral foraging strategy was determined based on taxonomy and published studies using GPS
trackers indicating a foraging range over 200 km without consistent trips back to the colony
during non-breeding seasons (Adams et al., 2016; Shoji et al., 2016). All Charadriiformes and
Phaethontiformes were classified as central foragers while all Procellariiformes were classified
as non-central foragers (Guilford, et al., 2008; McDuie et al., 2015; Le Corre et al., 2012). Most
Suliformes were central foragers, with the exception of the Northern Gannet (Morus bassanus)
9
and Great Frigatebird (Fregata minor); Thaxter et al., 2012; Gilmour et al., 2012). Wing load
was calculated as average mass (g) over average wingspan (cm) since wing surface area was not
available for most species.
Genetic data
A cladogram for all 36 species of seabirds in this study was built using concatenated
nucleotide sequences of mitochondrial genes cytochrome b (cyt b), 12S ribosomal RNA (12S),
cyclooxygenase (COX), ATP synthase subunit 6 (ATP6), and NADH dehydrogenase subunit 2
(ND2), and nuclear gene recombination activating gene 1 (RAG1). Sequence data from 35
species were obtained from a previously published seabird study (Hughes & Page, 2007).
Concatenated nucleotide sequences of the Hawaiian Petrel (Pterodroma sandwichensis) were
also added to the initially published alignment (NCBI accession numbers: HQ420351-HQ42080,
HQ918211-HQ918230, JF264905-JF26972, and JN015536-JN016231). Individual seabird
species were then grouped by taxonomic order and aligned to produce a cladogram (Figure 1.3).
The tree was constructed using the software program Geneious (Kearse et al., 2012) with a
Tamura-Nei model under neighbor-joining tree build method, creating a consensus bootstrap tree
with 1000 replicates and a 50% support threshold.
Statistical analysis
We applied principle components analysis and a linear mixed-effects model to the data,
depending on the nature of the test variable, to understand each dispersal variable’s relationship
to philopatric rates among seabird species. We also computed Pearson’s correlation coefficient,
to measure the strength of variables to philopatry, and effect sizes (Cohen’s d) to facilitate
10
comparison across other studies and datasets. All statistical analyses were conducted in the
statistical environment of R version 3.3.3 (R Core Team, 2013).
The relationships of variables to rates of philopatry were measured using a linear mixedeffects model. All quantitative variables were transformed to meet the assumption of normality
under linear regression using the skewness test for normality (Shapiro et al., 1968). A linear
mixed-effects model was developed for the entire dataset and split by region, tropical and
temperate, using R package ‘lme4’. The linear mixed-effect models allowed for the analysis of
philopatry at multiple colonies across species. We designated each species as an individual group
to account for potential bias due to the uneven sampling across seabird colonies. Random effects
across colonies were grouped by species while explanatory variables were designated as fixed
effects. The linear mixed-effects models allowed for variance-weighted averaging by species
when determining significance between philopatry and explanatory variables. Multiple iterations
of the model were performed, removing non-significant variables one at a time, to produce the
model with the best fit.
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RESULTS
We evaluated whether extreme cases of behavioral philopatry in seabirds were simply in
line with predictions based on colony demographics, or were indeed a paradox. Based on our
study, data from banding and census studies suggested that philopatric rates are higher in the
tropical region, the Procellariiformes order, and for non-central foragers. Our results indicated
the seabird paradox holds true for some seabird taxonomic groups, but not others.
When compared to the relative proportion of individuals in each colony, seabirds
returned to their natal colony at higher rates than expected, with Procellariiformes, non-central
foragers, and tropical region having a significant effect on philopatry (Table 1.2). Philopatry had
a weak slope toward colony size (Figure 1.4). Under the model with the best fit, the significant
independent variables explained 49.2% of the variance (R2=0.492) within philopatry rates.
Philopatry was significantly higher in the Procellariiformes order than in the other seabird
taxonomic orders (t464= 2.44, P = 0.0211; Figure 1.5). Additionally, seabird philopatry had a
significant relationship with region (t464 = 2.766, P = 0.0100) and non-central foraging strategy
(t464 = -2.40, P = 0.0229) (Figure 1.6). When split by region, the same dispersal factors, as well
as colony size, were significantly associated with philopatry in the tropical seabird colonies
(Table 1.3). For temperate seabird colonies, the only significant relationship to philopatry was
that with distance to the closest colony (Table 1.4).
The principle components analysis showed the variation found within the seabird dataset.
We saw clustering by taxonomic order based on colony-level quantitative variables (wing load,
philopatric rate, colony size, number of colonies, and distance from the natal colony) (Figure
12
1.7). The first principle component explained 41.8% of the variation within the dataset with
colony size and distance having the highest correlation coefficients.
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DISCUSSION
We investigated whether behavioral philopatry in seabirds was based on colony
demographics or a product of other mechanisms of dispersal. Although not directly proportional,
colony size was positively correlated with philopatry rates. This suggested that relative colony
size is an important consideration when making inferences about philopatric rates from single
study locations, especially large colonies where people might be more inclined to conduct
research. This may lead to the conclusion that high philopatric rates are more common in
seabirds than actually true (Coulson, 2016).
Both seabirds under the order of Procellariiformes and those exhibiting a non-central
foraging strategy returned to their natal colony at higher rates than other seabirds orders
(Charadriiformes, Suliformes, and Phaethontiformes) than those with a central foraging strategy.
These variables explained 49.4% of variation within philopatric rates of seabirds, which was
noteworthy considering the complex behavior of dispersal. As all Procellariiformes in the study
were identified as non-central foragers, the results indicated a linked dispersal pattern to
taxonomy and foraging behavior. Furthermore, our study validated previously published trends
within the Procellariiformes and non-central foragers. Extensive banding records of Albatross
families, in the Procellariiformes order, have exemplified the ‘seabird paradox’, showing over
99% return rates to some colonies (Weimerskirch et al., 1984; Fisher, 1976). Additionally,
seabird restoration programs have had the highest success within the Procellaridae family, with
translocated chicks returning at high rates to the new colony (Jones & Kress, 2011).
The same relationship between philopatry, foraging strategy, and taxonomic order was
found in tropical seabird colonies but not in the temperate seabird colonies, potentially due to the
14
low sample size of Procellariiformes within the temperate region (N=2). Furthermore, the
Northern Fulmer (Fulmarus glacialis), one of the two species of Procellariiformes in our study
surveyed in the British Isles, had a much lower philopatric rate (43%) than other species of
Procellariiformes in the study. The Northern Fulmar underwent a recent expansion in the British
Isles, suggesting other factors may have driven dispersal, such as a change in food availability, a
genotype favoring range-expansion and colonization, or the gradual warming of the eastern
Atlantic during the last century (Lloyd et al., 2010). Overall Procellariiformes had high
philopatric tendencies, but there were exceptions within the order.
Within temperate seabird colonies, philopatry was positively correlated with the distance
to the closest colony. Most seabirds surveyed in the British Isles were central foragers with
smaller home ranges, thus having less potential to disperse to colonies at far distances.
Potentially, seabirds were more likely to return to their natal colony due to lack of available
surrounding colonies within dispersal range. Additionally, other studies looking at seabird
dispersal concluded a significant driver was the distance from the source colony, indicating
distance may be an important factor for some species, but not all seabirds (Buxton et al., 2014;
Oro et al., 2011; Hénaux et al., 2007).
The higher philopatric rates in the tropical region than in temperate colonies may be
slightly biased due to higher sampling of Procellariiformes in the tropical region. However,
conditions in this region may favor Procellariiformes and philopatric behavior. The difference in
predator composition of Hawai‘i, comprised of isolated oceanic islands, and the British Isles,
made up of continentally-adjacent islands, is explained by the theory of island biogeography
(MacArthur & Wilson, 2016). Seabird colonies in the Hawaiian Islands, hosting a chain of
islands remotely isolated in the Pacific Ocean, formed by undersea volcanos, evolved without
15
connection to a continent and without mammalian predators (Stearns, 1946). In contrast, the
British Isles were connected to Europe during the last glacial period by a plateau called
Doggerland, allowing for the dispersal of mammalian predators (Montgomery et al., 2014).
Hawaiian colonies may have a greater rate of return because they have historically provided a
consistently predator-free or minimum-predation nesting habitat. Tropical waters surrounding
Hawai‘i have fewer resources than those at high latitudes, but the benefit of nesting in Hawai‘i’s
minimum-predation atolls may outweigh the risk, following the foraging/predation risk trade-off
behavior (Verdolin, 2006). The risk of predation has been previously shown to influence
population movement in terns and skimmers (Coulson, 2016). Additionally, breeding success has
been negatively correlated with the abundance of predators (Oro et al., 2011; Smith et al., 2002;
McChesney & Tershy, 1998).
Other environmental drivers may also account for the difference in regional philopatry.
Many of the seabirds observed in Great Britain and Ireland were coastal, inland, and roof nesters
that breed in many locations within a county, allowing more options for dispersal in this region.
Coastal seabird colonies tend to be more stable in occupancy than in inland colonies, most likely
due to higher predictability regarding access to food in coastal colonies than inland colonies
(Schreiber & Burger, 2002). In England and Wales, seabirds readily moved between inland sites,
depending on factors such as disturbance and water levels, which may be responsible for the
fluctuation in numbers at many colonies (Gribble, 1979). The British dataset contained a high
number of inland colonies, while the Hawai‘i dataset had primarily coastal colonies, which may
account for some differences in philopatry.
Primary productivity near foraging grounds may also have driven dispersal patterns. In
the tropical regions, adults invest less time in intensive chick guarding than temperate seabirds
16
due to longer foraging trips (Nelson, 1983). For example, Masked Boobies (Sula dactylatra)
leave their young to forage for food as soon as they can thermoregulate. In comparison,
temperate species like the Northern Gannet (Morus bassanus) guard offspring continuously until
fledging. Also, tropical pelagic Pelecaniformes return to their chick with food less frequently
than inshore temperate seabirds (Nelson, 1983). Due to the need to forage for longer durations in
the tropics, there may be more pressure for seabirds to leave their young in predator-free
colonies, where needs for parental protection are minimal. Similarly, migrating terrestrial
mammals in the temperate regions shift migrate during warmer months to high altitude and
latitude grazing grounds to give birth in areas of higher quality habitat and lower predation
(Fryxell & Sinclair 1988, Sawyer et al. 2009). Foraging and predation risk trade-off behaviors
found in herbivorous cervids may similarly be found within tropical seabird colonies (Geist,
1998). Thus, tropical colonies, for example, predator-free remote atolls, may hold higher quality
seabird habitat, leading to increased population stability and higher rates of natal philopatry.
We addressed some potential dispersal variables across seabird species in this study, but
other confounding variables were likely at play. For example, the presence of other species of
seabirds may have influenced philopatry. Congeneric species may act as a social attraction as
observed within Short-tailed Albatross (Phoebastria albatrus) (Deguchi et al., 2012). In contrast,
other seabird species may serve as competitors reducing philopatry. For examples, Wedge-tailed
Shearwaters (Ardenna pacifica) outcompete Newell’s Shearwater (Puffinus newelli) for preferred
burrowing space (Raine & Vynne, 2016) and Black-legged Kittiwakes (Rissa
tridactyla) outcompete Common Guillemots (Uria aalge) for space during population booms
(Durant et al., 2011). Additionally, sex may influence dispersal as seen in other long-lived
species (Chang et al., 2014; Bowen et al., 2005). Studies have shown no sex difference (Milot et
17
al., 2008; Munilla et al., 2016) as well as male-mediated (Greenwood, 1980; Young, 2010) and
female-mediated (Steeves et al., 2005; González-Jaramillo & Rocha-Olivares, 2011) within
seabirds suggesting species-level variation. Furthermore, changes in food availability highly
influence dispersal. For example, young Long-tailed Jaegers (Stercorarius longicaudus) have
been known to move to new areas where there was higher food availability (Barraquand et al.,
2014).
Seabird populations are decreasing globally with many colonies vulnerable to climate
change and land-use change, leading to potential ecological traps under continued philopatric
behavior (Mitchell et al., 2004). Although philopatry in seabirds is complex, this study indicated
that Procellariiformes, non-central foraging behavior, and tropical region may be responsible
some of the underlying mechanisms driving natal site fidelity. Continued research on philopatry
across multiple spatial scales within more seabird species is required to support these findings.
Seabirds return to their natal colony at higher rates than expected based colony size, making
seabirds fit candidates for successful translocation, especially those in threatened colonies. Our
study suggests that translocation programs will be more successful for species in the order
Procellariformes, as well as for species in tropical regions, and those with non-central foraging
strategies, as these species are more likely to return to translocation sites.
18
Table 1.1. Summary of taxa analyzed (N=36), with colony and species associated attributes as
well as average philopatric rates for species and range at colonies
Species
Sooty Tern
(Onychoprion fuscatus)
Gray-backed Tern
(Onychoprion lunatus)
Arctic Tern
(Sterna paradisaea)
Little Tern
(Sternula albifrons)
Common Tern
(Sterna hirundo)
Sandwich Tern
(Thalasseus sandvicensis)
White Tern
(Gygis alba)
Black-Headed Gull
(Chroicocephalus
ridibundus)
Common Gull
(Larus canus)
Herring Gull
(Larus argentatus)
Lesser Black-backed Gull
(Larus fuscus)
Great Black-backed Gull
(Larus marinus)
Black-legged Kittiwake
(Rissa tridactyla)
Brown Noddy
(Anous stolidus)
Black Noddy
(Anous minutus)
Razorbill
(Alca torda)
Atlantic Puffin
(Fratercula arctica)
Black-footed Albatross
(Phoebastria nigripes)
Laysan Albatross
(Phoebastria immutabilis)
Tristram’s Storm Petrel
(Oceanodroma tristrami)
Wedge-tailed Shearwater
(Ardenna pacificus)
Newell’s Shearwater
(Puffinus newelli)
Christmas Shearwater
(Puffinus nativitatis)
Wing
Load
Number of
Colonies
Observed
Percent
Philopatric
Range of
Philopatry at
colonies
Order
Region
Foraging
Strategy
Charadriiformes
Tropical
Central
2.27
11
0.82+/-
0.69 – .96
Charadriiformes
Tropical
Central
4.66
9
0.91+/-
0.88 – 0.97
Charadriiformes
Tropical
Central
2.81
92
0.72+/-
0–1
Charadriiformes
Temperate
Central
2.27
15
0.42+/-
0–1
Charadriiformes
Temperate
Central
16.38
21
0.18+/-
0 – 0.88
Charadriiformes
Temperate
Central
1.61
21
0.20+/-
0–1
Charadriiformes
Tropical
Central
1.49
11
0.93+/-
0.79 – .99
Charadriiformes
Temperate
Central
4.34
58
0.75+/-
0–1
Charadriiformes
Temperate
Central
6.84
66
0.63+/-
0.33 – 0.76
Charadriiformes
Temperate
Central
5.42
100
0.64+/-
0–1
Charadriiformes
Temperate
Central
1
31
0.50+/-
0–1
Charadriiformes
Temperate
Central
10.78
65
0.55+/-
0.08 – 0.82
Charadriiformes
Temperate
Central
1.89
90
0.72+/-
0 – .95
Charadriiformes
Tropical
Central
9.29
12
0.88+/-
0.57 – .91
Charadriiformes
Tropical
Central
16.33
12
0.77+/-
0 – .91
Charadriiformes
Temperate
Central
10.65
51
0.84+/-
0.14 – 0.96
Charadriiformes
Tropical
1.5
37
0.92+/-
0.38 - 1
Procellariiformes
Tropical
15.89
10
0.98+/-
0.35 - .99
Procellariiformes
Tropical
4.43
6
0.98+/-
0.05 – .99
Procellariiformes
Tropical
1.55
6
0.97+/-
0.8 – 1
Procellariiformes
Tropical
3.88
18
0.96+/-
0.83 – 1
Procellariiformes
Tropical
4.74
4
0.88+/-
0.87 – 0.87
Procellariiformes
Tropical
Central
NonCentral
NonCentral
NonCentral
NonCentral
NonCentral
NonCentral
1.49
18
0.91+/-
0.89 – 1
19
Bulwer’s Petrel
(Bulweria bulwerii)
Manx Shearwater
(Puffinus puffinus)
Northern Fulmar
(Fulmarus glacialis)
Bonin Petrel
(Pterodroma hypoleuca)
Hawaiian Petrel
(Pterodroma
sandwichensis)
European Shag
(Phalacrocorax
aristotelis)
Great Cormorant
(Phalacrocorax carbo)
Brown Booby
(Sula leucogaster)
Masked Booby
(Sula dactylatra)
Red-footed Booby
(Sula sula)
Northern Gannet
(Morus bassanus)
Great Frigatebird
(Fregata minor)
Red-tailed Tropicbird
(Phaethon rubricauda)
Procellariiformes
Tropical
Procellariiformes
Temperate
Procellariiformes
Temperate
Procellariiformes
Tropical
NonCentral
NonCentral
NonCentral
NonCentral
Procellariiformes
Tropical
Suliformes
2.18
11
0.95+/-
0.89 – 1
2.27
15
0.88+/-
0.64 – 1
10.78
65
0.43+/-
0 – 0.61
1.61
18
0.99+/-
0.8 – 1
NonCentral
6.44
8
0.79+/-
0.82 – .82
Temperate
Central
19.51
52
0.72+/-
0.09 – .82
Suliformes
Temperate
Central
4.41
75
0.25+/-
0 – .83
Suliformes
Tropical
Central
3.04
6
0.89+/-
0–1
Suliformes
Tropical
Central
11.59
11
0.95+/-
0.67 – 0.98
Suliformes
Tropical
6.41
12
0.83+/-
0.62 – .92
Suliformes
Temperate
21.72
69
0.15+/-
0 – .70
Suliformes
Tropical
Central
NonCentral
NonCentral
1.37
11
0.42+/-
0 – .6
Phaethontiformes
Tropical
Central
6.88
17
0.94+/-
0.89 – 1
20
Table 1.2. Dispersal variables from all seabird taxa (N=36) with comparison to rate of philopatry
using a linear mixed-effects model
Dispersal variable
Seabird Species from Temperate and Tropical Colonies
x̄ ± SE
t-value
P
Effect Size
Number of Colonies
4667 ± 1.394e-05
t464=-0.843
0.4082
d=1.737
r=-0.311
Colony Size
Distance to Closest
Colony
0.204 ± 6.159e-03
t464=1.715
0.0870
d=-0.221
r=0.162
-0.5342 ± 2.446e-01
t464=1.511
0.1314
d=-4.445
r=0.325
1.639 ± 4.795e-02
t464=0.372
0.7126
d=1.754
r=-0.021
1 ± 1.569e-01
t464=-2.402
0.0229*
d=1.897
-
Wing Load
Foraging Strategy(1)
a
b
Pearson’s r
Taxonomy(2)
2 ± 2.142e-01
t464=0.712
0.4816
d=1.461
b
Taxonomy(3)
3 ± 1.224e-01
t464=-0.528
0.6023
d=1.461
Taxonomy(4)b
4 ± 1.824e-01
t464=2.438
0.0211*
d=1.461
c
Region(1)
1 ± 8.809e-02
t464=2.766
0.0100*
d=1.926
a
1 = Non-Central Foraging Strategy, 2 = Central Foraging Strategy
b
Taxonomy: 1= Charadriiformes, 2= Phaethontiformes, 3=Suliformes, 4=Procellariiformes
c
1 = Tropical, 2 = Temperate
*number of colonies, wing load, distance to closest colony, and colony size percentage were transformed to meet
assumptions of normality.
21
Table 1.3. Dispersal variables from seabird taxa in tropical colonies (N=19) with comparison to
rate of philopatry using a linear mixed-effects model
Dispersal variable
Seabird Species for Tropical Colonies
x̄ ± SE
t-value
P
Number of Colonies
121 ± 0.0004
Colony Size
Distance to Closest
Colony
Wing Load
Foraging Strategy(1)
a
Effect Size
Pearson’s r
t102=-1.540
0.1488
d=2.394
r=0.016
1.047 ± 0.0108
t102=2.078
0.0405*
d=0.170
r=0.140
-0.474 ± 0.5069
t102=-1.344
0.1823
d=-6.467
r=-0.056
1.570 ± 0.0614
t102=-2.148
0.0557
d=1.244
r=-0.118
1 ± 0.1752
t102=-3.288
0.0076*
d=1.704
-
Taxonomy(2)
b
2 ± 0.1965
t102=2.057
0.0636
d=2.315
-
Taxonomy(3)
b
3 ± 0.2111
t102=1.627
0.1368
d=2.315
-
b
Taxonomy(4)
4 ± 0.1421
t102=3.826
0.0026*
d=2.315
1 = Non-Central Foraging Strategy, 2 = Central Foraging Strategy
b
Taxonomy: 1= Charadriiformes, 2= Phaethontiformes, 3=Suliformes, 4=Procellariiformes
*number of colonies, wing load, distance to closest colony, and colony size percentage were transformed to meet
assumptions of normality
a
22
Table 1.4. Dispersal variables from seabird taxa in temperate colonies (N=17) with comparison
to rate of philopatry using a linear mixed-effects model
Dispersal variable
Seabird Species from Temperate Colonies
x̄ ± SE
t-value
P
Effect Size
Pearson’s r
Number of Colonies
5950 ± 0.00002
t361=-1.010
0.3365
d=2.526
r=-0.0231
Colony Size
Distance to Closest
Colony
-0.036 ± 0.11016
t361=0.865
0.3877
d=-0.359
r=0.0389
-0.551 ± 0.27943
t361=2.161
0.0313*
d=-4.998
r=0.1269
1.658 ± 0.07219
t361=1.365
0.2011
d=1.929
r=0.0314
1 ± 0.24711
t361=-1.044
0.3189
d=2.396
-
3 ± 0.28667
t361=-1.458
0.1761
d=1.370
-
Wing Load
Foraging Strategy(1)
Taxonomy(3)
b
a
b
Taxonomy(4)
4 ± 0.19321
t361=1.037
0.3216
d=1.370
1 = Non-Central Foraging Strategy, 2 = Central Foraging Strategy
b
Taxonomy: 1= Charadriiformes, 2= Phaethontiformes, 3=Suliformes, 4=Procellariiformes
*number of colonies, wing load, distance to closest colony, and colony size percentage were transformed to meet
assumptions of normality
a
23
Percent Philopatry
(a)
Colony Size Percentage
Percent Philopatry
(b)
Colony Size Percentage
Percent Philopatry
(c)
Colony Size Percentage
Figure 1.1: Graphs of hypotheses of predicted seabird philopatry as (a) proportional to colony
size as percentage, (b) consistent with seabird paradox, and (c) following random distribution
24
Figure 1.2: Map of locations of all seabird colonies surveyed (N=465), with extent indicators on
the Hawaiian archipelago (HI) and British Isles (BI)
25
Figure 1.3: Cladogram of all seabird species surveyed (N=36) by taxonomic order
26
Figure 1.4: Graph of colony size as a percentage of total population size (P=0.0870) compared
to percent philopatry to all seabird colonies (N=465). Colony size percentage was log
transformed to meet assumptions of normality.
27
Figure 1.5: Graph of colony size as a percentage of total population size compared to percent
philopatry to colonies by taxonomic seabird order. Colony size percentage was log transformed
to meet assumptions of normality. Procellariiformes were consistent with the seabird paradox
(P=0.0211); However, colony size had a small positive effect on philopatry. The Suliformes and
Charadriiformes (P=0.6023) showed no relationship between colony size and philopatry.
Phaethontiformes were removed from final analysis because there was only a single species
represented.
28
(b)
Percent Philopatry
Percent Philopatry
(a)
log (Colony Size Percentage)
log (Colony Size Percentage)
Figure 1.6: Graphs of colony size as a percentage of total population size compared to percent
philopatry to seabird colonies by (a) region (P=0.0100) and (b) foraging strategy (P=0.0229).
Colony size percentage was log transformed to meet assumptions of normality.
29
Figure 1.7: Principle component analysis using quantitative variables (wing load, colony size,
number of colonies, and distance from the natal colony) from all seabird colonies (N=465)
grouped by order
30
CHAPTER 2
POPULATION GENETICS OF THE BAND-RUMPED STORM PETREL (OCEANODROMA
CASTRO), AN ENDANGERED AND ELUSIVE HAWAIIAN SEABIRD
31
ABSTRACT
Philopatry, the behavior of returning to the natal site to breed, limits dispersal and
presents a conundrum for genetic diversity. A higher degree of philopatry is found within
Procellariiformes, a seabird order that comprises of albatross, shearwaters and petrels, storm
petrels, and diving petrels. As a high rate of philopatry implies limited dispersal among
populations, lower genetic diversity may be expected assuming equilibrium, within
Procellariiformes compared to Charadriiformes, a seabird order that includes terns, gulls, and
auks that are not considered to be philopatric. Furthermore, species within Procellariiformes that
have experienced bottlenecks and thus lowered effective population size would be expected to
have even lower genetic diversity. In this study, we evaluated genetic diversity measures in the
only known populations of the endangered Band-rumped Storm Petrel (BSTP; Oceanodroma
castro), a species in the highly philopatric Procellariiformes order. We then compared published
genetic diversity measures between species in two orders with divergent rates of philopatry, the
Procellariiformes and Charadriiformes, to determine whether genetic diversity is significantly
different between these groups. We utilized next-generation sequencing to evaluate patterns in
genetic diversity in BSTP populations on the only two confirmed islands to host breeding
populations. Results indicated moderate genetic differences between populations and higher
genetic diversity than expected. Furthermore, we found no difference in genetic diversity
between species in the order Procellariiformes and those in Charadriiformes, contrary to
predictions based on significant differences in philopatric rates. Although species may be
behaviorally philopatric, the variation within genetic diversity within Procellariiformes indicated
that they are not genetically philopatric. This may be explained by sex-biased gene flow or other
32
mechanisms of complex population structure. Findings from this study may be used to inform
seabird conservation efforts, especially those managing genetic diversity and connectivity of
threatened colonies.
33
INTRODUCTION
Philopatry, the behavior of returning to the natal site to breed, may provide predictable
resources, mates, and safety, but also increases the potential for inbreeding, competition, and
ecological traps if habitat has since been degraded. Highly philopatric species, which limits
migration, may thus have lower genetic diversity than related species with higher rates of gene
flow (Mitton, 2001). A significantly higher rate of philopatry is found in species in the order
Procellariiformes, compared with other seabirds (Chapter 1). Philopatry has been found to
influence genetic patterns in some Procellariiformes (Ovenden et al., 1991; Levin & Parker,
2012; Welch, 2011; Milot et al., 2008). As philopatry limits dispersal between populations, lower
genetic diversity would be expected within Procellariiformes compared to Charadriiformes
(Chapter 1).
Species that have undergone historical bottlenecks, significantly decreasing population
size, are more likely to have decreased effective population and have even lower genetic
diversity (Avise, 2012). Effective population size is the number of breeding individuals in a
population while population size the number of individuals in a population. Given a high rate of
philopatry, combined with a historic bottleneck, we would predict that endangered species in the
order Procellariiformes would have lower measures of genetic diversity than other species
without these risk factors (Mitton, 2001; O’Brien, 1994). The Band-rumped Storm Petrel (BSTP;
Oceanodroma castro), an endangered seabird in the order Procellariiformes that nests on the
Main Hawaiian Islands, is predicted to have low genetic diversity based on its Endangered status,
an assumed low population number due to low rates of detection, presumed historical population
loss based on previous records and presence in midden sites across the Main Hawaiian Islands
34
(Pyle & Pyle), and an expected high rate of philopatry similar to closely related species (Friesen,
2015). The endangered BSTP is among the least commonly observed nesting seabirds in
Hawai‘i, and therefore difficult to study, with only two confirmed burrows known in the
Hawaiian Archipelago (Galase et al., 2017). One of the only tools currently available to assess
the remaining individuals is those of genetics. With potentially only a limited number of
individuals remaining (Pyle & Pyle, 2017), the populations may have problems normally
associated with small numbers, including demographic stochasticity and inbreeding (Kennedy,
2009). In this study, we sampled 10 of the remaining individuals (five per island) to evaluate
patterns in genetic diversity and connectivity between the two confirmed island populations in
the Hawaiian Archipelago.
The objectives of this study were to: (1) evaluate genetic diversity in an endangered
species, the BSTP, with a high rate of philopatry and potentially recent decline (Pyle & Pyle,
2017); (2) develop microsatellite markers useful for population-level studies, to complement
nuclear and mitochondrial markers developed for a global study of BSTP (Smith, 2007); (3)
compare genetic structure of BSTP populations in the Hawaiian Archipelago to global
populations of O. castro; and (4) compare genetic diversity between species in the orders
Procellariiformes with Charadriiformes, to evaluate predictions based on differing rates of
philopatry between these groups.
35
METHODS
Sample collection
Source populations of BSTP included slot canyons along the Honopu Valley and Waimea
Canyon on the island of Kaua‘i and breeding areas on the Pōhakuloa Training Area (PTA) on the
island of Hawai‘i, the only two confirmed breeding populations in the Hawaiian islands (Figure
2.1). Kaua‘i and Hawai‘i islands represent the northern and southern extent of the main Hawaiian
Islands and are approximately 300 miles apart (Figure 2.1).
Blood samples from the metatarsal vein from individuals on Kaua‘i were collected by the
Kaua‘i Endangered Seabird Recovery Project, a Hawai‘i Department of Land and Natural
Resources, Division of Forestry and Wildlife project, from birds captured using conspecific
playback and mist-netting techniques. Blood samples from one BSTP at Porters Landing Zone
(LZ), Waimea Canyon and four individuals from Honopu, Kaua‘i were stored on filter paper.
One other sample, supplied by the Kaua‘i Endangered Seabird Recovery Project, was a blood
sample collected from a downed fledgling from Kaua‘i. Samples from individuals on Hawai‘i
island were collected by the PTA Natural Resources Office, using dog and personnel searches.
Samples included flight feathers from five individuals, collected from individual carcasses or
found near nest sites, from the southeast portion of PTA.
Laboratory analyses
DNA was individually extracted from the blood and feather samples using the DNeasy
Blood and Tissue Kit (Qiagen, Valencia, CA) according to the manufacturer’s protocol. The
extracted DNA was quantified with the AccuClear™ Ultra High Sensitivity dsDNA Quantitation
36
Kit (Biotium, Hayward, CA) using two rows of eight standards. Due to low DNA yield, whole
genome amplification was performed on individual samples with the REPLI-g UltraFast Mini-kit
(Qiagen, Valencia, CA) which effectively increases yields of high-fidelity DNA (Ahsanuddin et
al., 2017). Equimolar amounts of whole genomic DNA extracted from five blood samples from
Kaua‘i and five feather samples from Hawai‘i island were pooled by their respective population
(Kaua‘i, Hawai‘i) using the ezRAD protocol (Toonen et al., 2013) version 2.0 (Knapp et al.,
2016). The two pooled libraries were then digested with the frequent cutter restriction enzyme
DpnII from New England Biolabs® (Ipswich, MA) and fragments between 300 and 700 bp in
length were prepared for sequencing on the Illumina®MiSeq using the Kapa Biosystems
(Wilmington, MA) Hyper Prep kit. Laboratory work was conducted at the Hawai‘i Institute of
Marine Biology (HIMB) in the ToBo Lab at Coconut island in Kāne‘ohe Bay, O‘ahu, Hawai‘i.
Libraries were sent to Genetics Core Facility at HIMB and sequenced on the Ilumina®MiSeq
platform.
Genetic data analyses
Next-generation sequencing resulted in a total number of 9,266,904 paired-end reads. The
dDocent pipeline (Puritz, et al., 2014) was applied using the command-line environment in a
Unix-based system to assemble loci and detect single nucleotide polymorphisms (SNPs) within
the aligned sequences. Trimmed alignments were transformed to be run in Popoolation1
(Institute of Population Genetics, Vienna, Austria) and Popoolation2 (Institute of Population
Genetics, Vienna, Austria), using a sliding window analysis for measures of diversity including
fixation indices (FST), nucleotide diversity (π), Watterson estimator of diversity (θ), and Tajima’s
D (DT).
37
The number of SNPs shared between populations ranged from 4,672 at a minimum
coverage depth of 4x to 75 at a minimum coverage of 60x and maximum coverage of 200x. For
the subsequent analyses, we used a minimum coverage cutoff of 10 reads per nucleotide position,
which resulted in a total of 1,431 shared SNPs with 10 – 200x read coverage. We then calculated
genetic diversity indices based on 1,970 SNPs within the Hawaiʻi Island population and 36,572
SNPs within the Kauaʻi population, utilizing Popoolation1 with a 10 – 200x read coverage. We
calculated fixation indices based on all 1,431 SNPs shared SNPs utilizing Popoolation2.
The discrepancy between the number of SNPs identified in each population, Hawaiʻi
Island (1,970 SNPs) and Kauaʻi (36,572 SNPs) may be due to the state of initial sampling
material or population demographics. Samples from Hawaiʻi Island (N=5) included slightly
degraded feather samples that were found near nests in the colony. Samples from Kaua‘i Island
(N=5) included fresh blood samples collected from live birds. DNA extracted from feathers has
been found to be more questionable in quality than DNA extracted from blood samples, which
may account for the difference in observed SNPs (McDonald & Griffith, 2012). Another
explanation is that Kaua’i’s population is expected to have more individuals (Pyle & Pyle, 2017)
and thus a higher effective population size which is more likely to have a higher number of SNPs
within the population, causing the discrepancy.
Microsatellite identification was carried out using the pal_finder Perl script on the
RADseq reads which were filtered for several parameters: include loci with designed primers;
exclude loci where the primer sequences occurred more than once in the reads; only include loci
with ‘perfect’ motifs; and rank by motif size (Castoe et al., 2012). Default parameters included
optimal 50% GC percent for primers, 18 bp as the minimum length of primer, and an optimal
melting temperature of 60 degrees Celsius to identify at minimum six perfect dinucleotide repeat
38
units. PANDAseq was also utilized to filter out the best quality microsatellite in the reads.
PANDAseq identifies ‘perfect’ microsatellite markers as those with highest-quality bases,
checked for sequencing errors, and that contain suitable overlap (Masella et al., 2012).
Mircosatellites were not scored in this study but instead identified for the use in future studies.
To compare relationships among global populations with populations in this study, NGS
sequences for populations in the Hawaiian Archipelago were aligned to sequences from global
populations of O. castro accessible in GenBank (accession numbers: KU217330-KU217328,
KU863867-KU863946, KU863779-KU863846, KU863964-KU863985) using Geneious 6.0
(Biomatters, Newark, NJ). Construction of phylogenetic trees was carried out with MEGA7
(Kumar et al., 2016) using the Hawaiian Islands population along with those available in
GenBank (Azores, Galapagos, and Japan) (Fig. 2.2).
To isolate sequences from mitochondrial regions cytochrome b (cyt b) and control region
(CR) for comparison to other population genetics studies, our next-generation reads were aligned
to previously published cytochrome b and control region I & II sequences (accession numbers:
KU217339 & AY600297) in Geneious 6.0 (Biomatters, Newark, NJ). Overlap included a
fragment of cytochrome b (177 bp) and a fragment of control region I & II (236 bp).
Mitochondrial DNA fragments of cytochrome b and control region I & II were concatenated,
forming a 416 base pair region that was analyzed for population genetic diversity statistics using
TASSEL (Bradbury et al., 2007). TASSEL was implemented as it was designed to analyze
isolated genetic sequences, similar to other mitochondrial marker studies.
Other seabird mitochondrial studies
39
Population diversity statistics were compared between species in the seabird orders
Charadriiformes and Procellariiformes. Following a literature search of Web of Science, Google
Scholar, and OneSearch Mānoa, 44 published papers were identified that contained genetic
diversity measures for species in the seabird orders Charadriiformes and Procellariiformes.
Population genetics studies were included if they reported nucleotide diversity (π) population
statistics and surveyed a minimum of two populations. Majority of seabird population genetics
studies were based on mitochondrial genes. Only studies that included the mitochondrial control
region and cytochrome b were chosen to limit mutation rate bias. Some studies only supplied a
combined average nucleotide diversity for sequences from both the mitochondrial control region
and cytochrome b. In studies that gave estimates individually, the average diversity estimate was
used to keep with consistency.
We employed an independent samples t-test in the R computational environment version
3.3.3 (R Core Team, 2013) to compare the means of nucleotide diversity between two seabird
orders, Charadriiformes and Procellariiformes.
40
RESULTS
O. castro population genetics
We identified an FST of 0.108 (P=0.943) between the two extant Hawaiian island
populations, based on 1,431 SNPs. Tajima’s D (DT) was negative for both Kauaʻi (-0.112 ±
0.015) and Hawaiʻi Island (-0.103 ± 0.022). A negative Tajima’s D (DT) indicated an excess of
rare alleles within a population. Kaua‘i island population had a slightly lower nucleotide
diversity (π) (0.003 ± .001) and Watterson estimator (0.004 ± .001) than the Hawaiʻi island
population nucleotide diversity (π) (0.004 ± .001) and Watterson estimator (θ) (0.005 ± .001;
Table 2.1).
The concatenated mitochondrial fragments of cytochrome b and control region I & II
(416 bp) aligned with 13 sequences from this study. Based on these sequences, nucleotide
diversity (π) was found to be higher in the mitochondrial regions (0.079), than in the regions
across the entire genome as sampled in the next-generation sequencing alignments (Table 2.1).
The Watterson estimator (θ) was also higher in the mitochondrial regions (0.132) than across the
entire genome (Table 2.1). Tajima’s D (DT) was found to be negative in the mitochondrial region
(-0.456) (Table 2.1). This strong of a negative Tajima’s D (DT) indicated an excess of rare
polymorphisms, that may be generated by population expansion, selection, or most likely high
mutation rate in the species (Wares, 2010).
Microsatellite marker identification
41
Microsatellite discovery through pal_finder resulted in 6,451 microsatellite loci with
generated primers. Those loci filtered through PANDASeq resulted in 153 microsatellite markers
with identified primers (S1).
Global O. castro phylogenetic relationships among groups
The phylogenetic reconstruction of global populations of O. castro (Azores, Japan,
Galapagos, and Hawai‘i) was constructed with concatenated alignments of two nuclear markers
and one mitochondrial marker using a bootstrap Neighbor-joining Tajima-Nei model with 1000
replicates. The method created a genetic distance matrix based on the number of nucleotide
substitutions between each group: Azores, Japan, Galapagos, and Hawai‘i. The phylogenetic tree
resulted in clustering of Japanese and Galapagos populations with a bootstrap value of 72.
Samples from Japanese and Galapagos populations were more genetically similar to each other
than to populations from the Hawaiian Archipelago (Figure 2.3). Populations from the Azores
did not cluster to any other population with a significant bootstrap value.
Comparison of genetic diversity between seabird orders
We found 44 seabird population genetics studies that published nucleotide diversities
statistics within the control region and cytochrome b, resulting in a comparison of 23 species of
Charadriiformes and 21 species of Procellariiformes in this study (Table 2.2 & 2.3). Due to the
skewness of the data, π values were log transformed to produce a normal distribution assessed
with a Shapiro-Wilk normality test. Mean nucleotide diversity (π) was not significantly different
between Charadriiformes (0.007 ± 0.005) and Procellariiformes (0.010 ± 0.012) (P = 0.811, t43 =
0.241).
42
DISCUSSION
Despite their Endangered status with a potentially low population size and philopatric
tendencies, we found BSTP in the Hawaiian Archipelago had relatively high genetic diversity
and structure given the assumed life history. Furthermore, we did not find behavioral philopatry
to have a significant effect on genetic diversity, suggesting other mechanisms were driving
genetic diversity within seabirds.
We note that caution should be used when interpreting population genetics statistics for
only two populations and especially when inferring biology without demographic history, as FST
is best interpreted in a comparative, or relative, context (Marko & Hart, 2011). However, an FST
greater than 0.05 between these two islands, located at the northern and southern reaches of the
main Hawaiian Islands, suggested moderate differences among populations (Hartl & Clark,
1997). Previous RADseq analysis on these species globally indicated distinct population genetic
groups with having at least an FST of 0.14 (Taylor, 2017). Nevertheless, an FST of 0.108 was
higher than expected between two Hawaiian islands 300 miles apart compared to an FST of 0.14
between Japan and Hawai‘i approximately 4,000 miles apart (Taylor, 2017). Under equilibrium
Mills and Alendorf (1996) argue it only requires up to 10 migrants to have an FST of 0, thus an
FST of 0.108 indicated fewer than 10 migrants a generation within BSTP in the Hawaiian Islands.
Although results were based on a small sample size (N=10), other studies have shown even with
a small sample size (i.e. two individuals), accurate estimates of FST can be obtained with a large
number of SNPs (≈ 1,500) from RADseq data (Nazareno et al., 2017).
Nucleotide diversity estimates within the BSTP Hawaiian island populations were higher
than expected based on nucleotide diversity estimates from global populations of BSTP mtDNA,
43
other Procellariiformes mtDNA, and other seabirds gDNA. Nucleotide diversity of mtDNA for
populations of O. castro in the Hawaiian Archipelago (π=0.079) was higher than the average for
the global species (π=0.013; Smith, 2007), as well as higher than other Procellariiformes (mean
π=0.010; this study). Although we note caution when interrupting mtDNA genetic diversity
measurements because the low coverage generated from the NGS data overlap. Nucleotide
diversities based on gDNA of O. castro in the Hawaiian Archipelago were higher than those
found in some studies of other seabird species (Tigano et al., 2017; Dierickx et al., 2015) but not
all (Clark, 2017). Moderate rates of nucleotide diversity appeared to be present despite their
Endangered status and presumed low population size of the BSTP in the Hawaiian Islands.
Other recent studies found lower genetic differentiation metrics based on a NGS SNPs
approach (FST or ΦST range: 0.009 - 0.33) compared to those calculated based on only
mitochondrial sequences (FST or ΦST range: 0.44 – 0.91) for the same species, which was
consistent with our findings (Taylor, 2017; Clark, 2017; Tigano et al., 2017; Dierickx et al.,
2015). Most RADseq studies find lower values due to sampling across the whole genome which
includes both areas of high and low polymorphism, while marker approach studies focus on a
few chosen isolated sequences, like the mitochondrial genes, which are often more polymorphic
(Cariou et al, 2016). Although we found a difference in magnitude between gDNA and mtDNA
for O. castro, both produced similar trends in genetic diversity (π, DT, θ) (Table 2.1).
Although there was moderate genetic differentiation in the populations of BSTP in the
Hawaiian Archipelago, a higher genetic structure was found between island archipelagos of this
species, as evidenced mitochondrial, microsatellite, and ddRAD analysis (Taylor, 2017).
Furthermore, the constructed phylogenetic tree placed samples of the Hawaiian Archipelago
44
separately from other previously sampled global populations (Galapagos and Japan), which
supports the finding that populations from the Hawaiian Islands are genetically less similar to
those populations of O. castro found globally. Our results supported previous findings
identifying O. castro in the Hawaiian Islands as a distinct genetic group (Taylor, 2017), but we
note caution when interrupting the phylogentic tree (Figure 2.3) as it only consisted of three
markers with low coverage due to the broadened use of NGS data in comparison to published
markers.
Past research has shown genetic structure within seabird species was less a result of
philopatric tendencies, but instead linked to foraging range and non-breeding distribution
(Friesen et al., 2007). Genetic differentiation between global populations may be driven by
ocean currents and at-sea food abundance (Friesen et al., 2007; Taylor, 2017). Foraging strategy
has been correlated to population genetic structure within other marine organisms that rely on
cold-water upwelling systems (Cassens et al., 2005, Schlosser et al., 2009, Jeyasingham et al.,
2013). Ocean patterns influence foraging strategies, and seabirds exhibiting a local foraging
strategy may be more likely to return to breed within their natal archipelago. Thus, low genetic
differentiation within Procellariiformes within a focal archipelago may be due to complex
population structure (Bowen et al., 2005). Spatially complex marine animals, like seabirds,
mandate management to survey and conserve different units critical for population structure.
Although species in the order Procellariiformes are more philopatric on average than
Charadriiformes (Chapter 1) nucleotide diversity estimates were not significantly different
between seabird orders, in contrast to what has been predicted for highly philopatric species
(Ovenden et al., 1991; Levin & Parker, 2012; Welch, 2011; Milot et al., 2008). Nucleotide
diversity is driven by dispersal rate as well as the combined impact of effective population size,
45
mutation rates, and history, all of which are expected to vary across avian species and may be
driving the variation within the nucleotide diversity estimates (Nabholz et al., 2009). Currently,
of these three (dispersal rate, effective population size, mutation rate), mutation rates are debated
to be the best predictor of within-species mitochondrial diversity (Nabholz et al., 2009).
Although we only included nucleotide diversity estimates from two different genes in the
mitochondrial genomes, these regions have different mutation rates (Friesen et al., 2007).
Furthermore, in our comparison of seabirds orders we assumed species were at equilibrium, but
if demographic impacts persisted, history may be a stronger force driving the observed patterns
(Chan et al., 2014).
Although seabird orders had significantly different philopatric trends (Chapter 1), other
factors of migration may be greater drivers of genetic diversity. Banding records showed that no
single Procellariiformes was completely philopatric, with some dispersal between colonies in all
species (Chapter 1). This study’s results suggested only a small amount of gene flow is
necessary, less than ten migrants per generation, to homogenize genetic structure throughout the
metapopulation (Mills and Allendorf, 1996). Another possible explanation is that seabirds may
mate while on visiting forays at neighboring colonies, increasing gene flow, as evidenced by
female Laysan Albatross (Phoebastria immutabilis) in the Main Hawaiian Islands (Young et al,
2010). Within other philopatric species, it is known that they breed offsite, mating with males
from other colonies, prior to returning to a natal site to lay eggs (Bowen et al., 2005). Thus,
complex population structure for a species must be taken into account to interpret population
genetics.
There are many potential reasons for the high genetic diversity observed within
populations of O. castro in the Hawaiʻi Archipelago. A population bottleneck likely occurred
46
since the arrival of humans to the Hawaiian Islands 1100 years ago, due to habitat destruction
and introduced mammalian predators such as rats (Rattus sp.), cats (Felis castus) and
mongoose (Herpestes javanicus) (Pyle & Pyle, 2017). In some cases, relatively high genetic
diversity in a rare species can indicate that decline in population numbers was recent (Mortiz,
1994). A second possible explanation may be lengthy generation times, coupled with delayed
sexual maturity, that can postpone the loss of genetic variation (Kuo & Janzen, 2004). The
Band-rumped Storm Petrel is long-lived and has a generation time of 12 years, leading to
overlapping generations (Harrison, 1990). In addition, demography can contribute to the
retention of genetic diversity (Goossens et al., 2005). Relatively high genetic diversity despite
population decline has been observed in other long-lived seabird species (e.g. the Balearic
Shearwater Puffinus mauretanicus, Genovart et al., 2007; the Magenta Petrel Pterodroma
magenta, Lawrence et al., 2017; Buller’s Albatross Thalassarche bulleri, Van Bekkum, 2006).
Furthermore, even though the Band-rumped Storm Petrel most likely experienced population
decline in Hawai‘i, there may be more individuals than currently estimated (Pyle & Pyle,
2017), as only a few hundred individuals are needed to capture all of the genetic diversity in
population (Gaither et al., 2010).
Further research examining these populations of O. castro is recommended to understand
the connectivity between islands across the Hawaiian Archipelago. Assessment of genetic
diversity on other islands and gene flow among islands, as well as in comparison with extinct
colonies using historical samples, will facilitate understanding of the historical genetic context
and allow for the creation of haplotype networks and effective population size estimates of the
endangered populations. Furthermore, fixed SNPs identified between island populations in this
study (N=23) may create valuable diagnostic genetic markers to address evolutionary history and
47
assign unknown or bycatch individuals to a known extant population. Research adding more
individuals from multiple years of sampling will add to and support current findings.
Despite their Endangered status and indication of population loss, this study suggests
genetics of O. castro in the Hawaiian Islands currently do not warrant management concern.
Although BSTP do not appear to be in current danger of a genetically induced extinction vortex,
they remain vulnerable to other extinction vortexes (Gilpin & Soulé, 1986). Predator control and
related management efforts to ensure successful nesting will be crucial to recover endangered
populations of the Band-rumped Storm Petrel.
48
Table 2.1 Population genetic diversities for O. castro in Hawaiian island populations. gDNA
refers to the RADseq alignments and mtDNA refers to the concatenated mitochondrial sequence
of the control region and cytochrome b.
Population
DNA
Region
Nucleotide
diversity (π ± sd)
Watterson
estimator (θ ± sd)
Tajima’s D
(DT± sd)
FST
Kaua‘i
gDNA
0.004 ± 0.001
0.003 ± 0.001
-0.112 ± 0.015
Island
0.108
P=0.943
Hawai‘i
gDNA
0.005 ± 0.001
0.004 ± 0.001
-0.103 ± 0.022
Island
Kaua‘i &
Hawai‘i
mtDNA
0.079
0.132
-0.456
Island
* standard deviation of mtDNA was not included because the software used to produce the
genetics diversities, TASSEL, does not report them
49
Table 2.2 Comparison of mean nucleotide diversity within populations (π) from mitochondrial
studies of species in the order Procellariiformes (N=21)
Seabird
Black-footed Albatross
(Phoesbatris nigripes)
Black-browed
Albatross
(Thalassarche
melanophrys)
Grey headed-Albatross
(Thalassarche
chrysostoma)
Laysan Albatross
(Phoebastria
immutabilis)
Family
Marker
Cyt b
(609bp)
π (range)
0.0005 (0.000.0012)
Diomedeidae
CRI
(219bp)
0.02 (0.008-0.042)
Diomedeidae
CRI
(220bp)
0.03 (.0022-0.040)
Diomedeidae
CRI
(189bp)
0.045 (.030-.059)
Northern Fulmar
(Fulmarus glacialis)
Procellariidae
CRI
(299bp)
0.0107 (0.0079.0139)
Burg et al., 2003
Cory’s Shearwater
(Calonectris borealis)
Procellariidae
0.0132 (0.00230.024)
Gómez-Díaz, 2007
Scopoli Shearwater
(Calonectris diomedea)
Procellariidae
0.0139 (0.00370.024)
Gómez-Díaz, 2007
0.010 (0.0030.016)
Gómez-Díaz, 2007
≤ 0.004
Friesen et al., 2007
0.0144 (0.0015 –
.0272)
Genovart et al., 2007
0.0036 (.00080.00471)
Lombal et al., 2017a
0.0005 (.0003.0007)
Gangloff et al., 2013
0.0013 (.0011.0015)
Gangloff et al., 2013
Diomedeidae
Cape Verde Shearwater
Procellariidae
(Calonectris edwardsii)
Sooty Shearwater
(Puffinus griseus)
Balearic Shearwater
(Puffinus
mauretanicus)
Flesh-footed
Shearwater (Ardenna
carneipes)
Procellariidae
Procellariidae
Procellariidae
Deserta Petrel
(Pterodroma deserta)
Procellariidae
Cape Verde Petrel
(Pterodroma feae)
Procellariidae
CRI, Cyt
b
(1393bp)
CRI, Cyt
b
(1393bp)
CRI, Cyt
b
(1393bp)
Cyt b,
CRII
(695bp)
Cyt b,
CR
(1180bp)
Cyt b
(858 bp)
Cyt b,
CO1
(1604bp)
Cyt b,
CO1
(1604bp)
50
Paper
Walsh & Edwards,
2005
Burg & Croxall, 2001
Burg & Croxall, 2001
Young et al., 2010
Zino’s Petrel
(Pterodroma madeira)
Procellariidae
Providence Petrel
(Pterodroma solandri)
Procellariidae
Magenta Petrel
(Pterodroma magenta)
Procellariidae
Hawaiian Petrel
(Pterodroma
sandwichensis)
Gould’s Petrel
(Pterodroma
leucoptera)
Leach’s Storm Petrel
(Oceanodroma
leucorhoa)
European Storm Petrel
(Hydrobates pelagicus)
White-faced Storm
Petrel (Pelagodroma
marina)
Cyt b,
CO1
(1604bp)
Cyt b
(872bp)
Cyt b,
CRI & II
(1458bp)
0.0016 (.0009.0023)
Gangloff et al., 2013
0.0093 (0.00690.0117)
Lombal et al, 2017b
0.01387 (0.0013.0223)
Lawrence et al., 2007
0.00397 (0.003820.00409)
Procellariidae
Cyt b
(524bp)
Procellariidae
CRI, Cyt
b
(1327bp)
0.00115 (0.000630.0016)
Hydrobatidae
CRI, II
(357bp)
0.0055 (0.0050.007)
Bicknell et al., 2012
Hydrobatidae
Cyt b
(970bp)
0.0005 (0.00.0011)
Cagnon et al, 2004
Hydrobatidae
CRI, II
(522 bp)
0.0075 (.004-.011)
Silva, 2015
51
Welch, 2011
Iglesias-Vasquez et
al., 2017
Table 2.3. Comparison of mean nucleotide diversity within populations (π) from mitochondrial
studies of species in the order Charadriiformes (N=23)
Seabird
Ivory Gull (Pagophila
eburnea)
Lesser Black-backed
Gull (Larus fuscus)
European Herring Gull
(Larus argentatus)
Common Gull (Larus
canus)
Glaucous-winged Gull
(Larus glaucescens)
Glaucous Gull (Larus
hyperboreus)
Black-legged Kittiwake
(Rissa tridactyla)
Red-legged kittiwake
(Rissa brevirostris)
Family
Marker
π (range)
0.0016 (.0005.0027)
0.0028 (0.00180.0042)
0.0110 (0.0010.018)
0.0146 (0.010.024)
0.0137 (0.010.021)
0.0070 (0.0040.013)
0.0048 (0.0030.009)
0.0150 (.011.016)
Paper
Laridae
CR (264bp)
Laridae
CRI, Cyt b
(1573bp)
Laridae
CRI (430bp)
Laridae
CRI (430bp)
Laridae
CRI (430bp)
Laridae
CRI (430bp)
Laridae
CR I, II, III
(773bp)
Laridae
CRI (445bp)
Sooty Tern (Sterna
fuscata)
Laridae
RFLP, CRI,
II, III
(1399bp)
0.0210 (.018.026)
Peck & Congdon 2004;
Avise et al., 2000
South American Tern
(Sterna hirundinacea)
Laridae
Cyt b, ND2
(790bp)
0.0012 (0.00090.0017)
Faria et al., 2010
Least Tern (Sternula
antillarum)
Laridae
CR (840bp)
0.0050 (0.0010.007)
Draheim et al., 2010
Common Murre (Uria
aalge)
Alcidae
Cyt b
(204bp)
0.0040 (0.00260.0053)
Friesen et al., 1996a
Thick-bulled Murre
(Uria lomvia)
Alcidae
Cyt b
(253bp)
0.0076 (0.0036.0156)
Friesen et al., 1996a
Razorbill (Alca torda)
Alcidae
CRI (300bp)
Black Guillemot
(Cepphus grylle)
Alcidae
CRII, III
(504bp)
0.0130 (0.0093.0198)
0.0030 (0.000.0058)
Pigeon Guillemot
(Cepphus columba)
Alcidae
CRII, III
(504bp)
0.0087 (0.0047.0170)
52
Royston & Carr, 2016
Liebers et al., 2004
Sonsthagen et al., 2012
Sonsthagen et al., 2012
Sonsthagen et al., 2012
Sonsthagen et al., 2012
Patirana, 2000
Patirana et al., 2002
Moum & Arnason,
2001
Kidd & Friesen, 1998
Kidd & Friesen, 1998
Xantus’s Murrelet
(Synthliboramphus
hypoleucus)
Ancient Murrelet
(Synthliboramphus
antiquus)
Marbled Murrelet
(Brachyramphus
marmoratus)
Kittlitz’s Murrelet
(Brachyramphus
brevirostris)
Crested Auklet (Aethia
cristatella)
Whiskered Auklet
(Aethia pygmaea)
Cassin’s Auklet
(Ptychoramphus
aleuticus)
0.0058 (0.0020.0094)
Alcidae
Cyt b
(1045bp)
Alcidae
CRI, II, III,
Cyt b
(1132bp)
0.0042 (0.0040.0044)
Pearce et al., 2002
Alcidae
Cyt b, CRI
(1592bp)
0.0070 (0.0028.0104)
Friesen et al., 1996b;
Friesen et al., 2005
Alcidae
Cyt b
(1045bp)
0.0024 (0.00170.0030)
Friesen et al., 1996b
Alcidae
CR (408bp)
Alcidae
CR (670bp)
0.0140 (0.0120.019)
0.0052 (.002.007)
Pshenichnikova et al.,
2015
Pshenichnikova et. al.,
2017
Alcidae
CR (706bp)
0.0061 (.004.008)
Wallace et al., 2015
53
Friesen et al., 2007
Main Hawaiian Islands
Figure 2.1 Collection sites of the Band-rumped Storm Petrel (Oceanodroma castro) across the
Main Hawaiian Islands
54
Figure 2.2 Global distribution of Band-rumped Storm Petrel (Oceanodroma castro) colonies (AS
– Ascension, AZ – Azores, CV – Cape Verde, FR – Farilhoes, GA – Galapagos, HI – Hawai‘i
Island, JP – Japan, KI – Kaua‘i Island, MD – Madeira)
55
Figure 2.3 Phylogenetic tree of global populations of Oceanodroma castro (nuclear and
mitochondrial markers) bootstrap Neighbor-Joining Tajima-Nei model constructed using
MEGA7. The bootstrap value of 72, indicates the percentage of replicate trees which the
associated taxa clustered together in the bootstrap test (1000 replicates). The other values are the
branch lengths in the same units as those of the evolutionary distances to infer the phylogenetic
tree (number of base substitutions per site).
56
Summary
This thesis represents a comprehensive examination of behavioral philopatry and patterns
of population genetics across seabird taxa. Our research goal was to further understand
behavioral and genetic philopatry within seabirds to inform conservation efforts. While some of
the hypotheses presented in this research were supported, others contradicted our predictions.
Seabirds provide an interesting challenge when studying population dynamics: many are
highly philopatric but also highly migratory, which influence dispersal and gene flow in
opposing directions. Within the exploration of behavioral philopatry through use of long-term
banding studies, we found dispersal to be less correlated to colony size and population structure
and instead linked to with foraging strategy, taxonomic order, and geographic region. Across
seabird orders, Procellariiformes, a historically philopatric order, showed no difference in genetic
diversity to those in the Charadriiformes, a less philopatric order. The Band-rumped Storm
Petrel, an endangered and philopatric seabird, had higher genetic diversity and population
structure than hypothesized in the Hawaiian Islands. Population genetics of the endangered O.
castro suggested moderate gene flow possibly due past population size, high mutation rates, and
complex population structure. Although BSTP populations in the Hawaiian Islands had relatively
high genetic diversity, there are still a multitude of threats to BSTP, from introduced predators to
climate change. This study suggests BSTP in the Hawaiian Islands do not appear to be in danger
of a genetics induced vortex but remain vulnerable to other threats (Gilpin & Soulé, 1986).
Consequently, management efforts should continue conservation actions at existing colonies and
seek to expand potential predator-free refuges, like Lehua Islet (Raine et al., 2017), to increase
population size within the Hawaiian Islands.
57
Appendix 1: Microsatellite markers (N=153) identified by PANDASeq using next-generation
ezRAD reads from Oceanodroma castro
Id
1
2
3
4
5
6
7
8
9
Forward Primer
TGCCTCAGCTGTTTGTTTCC
ACCAGGAAAATACCGAGGTCC
GATCCCTGCATAGAGCCTGC
CTCATCGTTTGATGAACCCG
GATCTGAGGGGTTAGTGGCG
CTTTCCATCCTCGCAATCG
ACAGCCTGTCCTGAGGATGC
TGTTCAGTTTATTGGCTTTTGCC
CTTCACTTAAGGCCCATGCC
10
11
12
13
14
15
16
CAACACGCACTTGAGACAGC
GATCCACCAAGAACCACACG
TCGACGATTTGTGTGTGTGC
ATGCCATTATCTTCACCGGG
TAAGATGCTGGTCGGTCGG
ATGGCCTTGCCAGAGATACC
AGTCATGAAAAGGAAGGCCC
17
18
GACCCACGCAGTCAAATCC
AACATTTACACATCGAGTAAGCA
GC
ATGCAGTACGGTGGCAAGG
TCACGTTTGGAGGAAAAGGG
GGCAATCCAACTCCAACTCC
CAAAGCCTGTGTTGCTGAGG
CCTAAGGGTAGGGATGTGGG
AGTGAGTGACAGCCTGGACG
GATGGTGGTGGATATGGACG
CAAACACTTCCCACCCAACC
CCAATGATAGACTAGACCGGCG
TTGTTGGACACTGTCGAGGC
GTGTGTTGCTGTGTTGCACG
GGTCTGAACTCTCAAAATATACA
GGC
19
20
21
22
23
24
25
26
27
28
29
30
Reverse Primer
GCAGCATGGAGGGAGATACC
ACACCCGTTATTGCTCAAAGG
CCTGTAAACTGTCCCCTGGC
AATTCATCCCATGTTTCACGC
ACGTGAACATGAATGACGGG
GAGGAAACGTGGAAAGGTGG
GATCATCCCTTTGTCCTGGG
GGCTGGATTTGAAGTGTGGG
GGTGGTACCAGTAGTGGTTTAGTG
G
CAGATGTAGCTGACGTACGGG
TGCTACCCTGTTTCAGCAGC
AATATCAATCTGCCGAGCCC
AAAACTGACTCCGCATTTTGC
AAATCAACATGTGGCCTCCC
CTATAAGACAGCACCCGCCC
GCACAAGGAAAGAAAGTGTAGTA
GG
CAGAGTCTGCTTAGGATTCTCCC
ACACTTCCAGAGGGGACCG
ATATGGCAGTCACGGTCACG
GATCCATGCTTGCTCCAGG
ACCTGAAGAAAACGCTTGGG
CTCCTATGTGTTGGGTCCGC
GAAGACACTGGAGCTGTTGACC
GTCTTCGGCGATACGAGCC
ACATTCCGGAGTTGGTTTCC
TGTGTGCATTTGTTTCTGCG
TGAGGGTCTCACATGTTCGC
TCAACACTGCCGTCTTCTCG
CAGCTTGATGGACGTTCTGC
TGGTGCATAAGTGTTCTCAATGG
58
Motifs
(bases)
TC(12)
TC(12)
TC(32)
TC(14)
AC(18)
TC(22)
AC(12)
AC(12)
AT(12)
AC(20)
AT(14)
AC(14)
TC(12)
AC(26)
AC(12)
TC(16)
TC(14)
AT(14)
AC(14)
AC(12)
TC(12)
AC(12)
AC(14)
AC(14)
AT(12)
AC(12)
AT(12)
TC(12)
AC(14)
AT(12)
31
32
33
34
35
36
37
38
39
40
TGTACAGTTCGTTCGTCCCC
CTGGCAGGGAGAATTATGGG
TGTACTAGCCATTGCCTGCC
GGTGCCTATAGTTGGCAGGC
TGTGTCGGGTCTTGTATGGG
CGAGTCTCACATTGGGCTCC
CTACAGCCAATGGCAACACC
GCAGAAACGAGAATGATGGG
TTAACATAAAACCTCCCACCCC
CCTTTGGCACAGAATGAAAGG
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
ACTGCAGCAGACACACAGGC
GGTCGAGGATATGCCTTCCC
TTTACCGATTCCGATGTGGC
CACAATTTATCTTGCCCGCC
CGGGGAACTAGTCATCGAGC
GGGTAGATCGAGCAAATCCG
ACCGCCCTTCTTCTACCTCC
TGCTTGCCAGTTCAATTTCG
ATGACACAGACTCGATGGGC
GCATGGCCTTTTCACTGTCC
TGCCACCAAGACTTCTTCCC
ATGTTTGAGCCCCATGTTGG
AGCTCTGATCTGCCCCTCC
CACCATGTCACCACCAAAGC
CCAGTCCTGTGACCATCAGC
CAAATCCCTGCAATTTTCGG
CAGTCGTGTAGCTTGCAGCC
TTTTGGGGCAATTTCTATGG
AATCCCAGTTGCAGACACCC
GCTCACCGGGAACTATTTGG
TCCTAAGGAATCTCGAGGCG
CTCTGCGGAGTTGTGACTCG
AGCCGAAGCCACAGTCTACC
GAAAAGCTGCTCAACGCTCC
GATCATGTGGTGAGATAAGCG
CTTCTGATTGTCACGAGCGG
GGAGACAGGAATGGGTGATGG
CTCTCCCATCTTCTCCCAGG
TGACTGCAGCAATCTTTGCC
CGGGTGAGCTGAGATTAGGG
ACTTTGCCTGCTGCATTTCC
CACATTGCCTTTACAGTTACTGCC
TCTGTCTCTTTGCAGACGGG
CGTCCAGAGTTGTCCCTTCC
CCTCGGAAGGAATCACTGACC
TCCAACTGGCAGTCAGAACG
TCTCTCTCTGCTGTGCCTGC
GAGACCAAAATAGACAGGAGAAG
AGC
ATAGGATGTGTGGGCAAGGG
TCACAGGAGAAGTCAAAGGGC
CTCATGGATAAAGGACCGGG
GAGATAGTCAAAGAGAGCCCTGC
CGACGTTGTTCGAGCAGG
CAAAGGATTGATTCCCTCCG
GTTGGTCGTCGTACTGGTCG
GGACTTTCCAGAAGTCGGGC
AAATACGTCGGACAGTCGGG
GTCTTCAAGGAGCCACTGGG
GCTAGATGTCGTGCTCGTGG
CTCCCTTGCTGTGTCATTGC
AGCCTGCTTCTCTCTTTGCC
ATGCCAACTCCTTGACCTCC
CAGATGGACCAAACAGCAGC
AAGAACTCACTTGGTGGCCC
TTTGTTGGAGGTTGCTGTGG
CTAATCCCTCCAAACCCTGG
AATGAAATGGCACAGCATGG
TAGCAAGTGCTCGTTCTCCG
CTTCCCCTTCTTCCATCCC
ACAAACCGACATACCCTGGC
ATTCGGTATAGCGACCGGG
TTCACCTCTGAGAGCATCCG
ATGTGTGAGGGAACAGGAGC
GCGAAACGGTTCTTCAAAGG
GCTATAGGCTGTCTGTCAGTGGC
GTCCAAGGGGAGAAGGAACC
59
AC(12)
TC(12)
AC(12)
AC(14)
TC(14)
TC(24)
AT(20)
AC(12)
AC(12)
TC(28)
AC(12)
TC(12)
AC(16)
AC(12)
TC(20)
AC(12)
AC(16)
TC(12)
TC(14)
TC(20)
TC(14)
AC(30)
TC(14)
TC(12)
TC(14)
AC(12)
AC(12)
AC(12)
TC(24)
TC(12)
TC(18)
AC(14)
AC(12)
AT(12)
AC(12)
TC(14)
AC(26)
TC(12)
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
GCAGCCAAGAAGACACATGG
GGAGGTCTGGGTTTCTGAGC
CCGTATCCAAAACAAAACGC
TTGCAAATTGCCCTTTATGG
GAAGAATTTCCCAGCAATCCC
CAACAGAAGCAGCTTGGACC
ATCCTGAAGACCCAGGATCG
CCCAGAGCTGAAGGGAAGG
CACAACCGTGACATCGAACC
TAGGTGCTCTGGCATTCTGC
AACCTCAGCTTCCTGCTTGC
CTTCCTTGTTCCACTTCGCC
ATACCCCACACTCCGTCTCG
GTACAAAGTGCCGTGCAAGC
ACACGCAACGTACCACAAGG
CACAGGTGAATTCAAGGGGC
CACAAGACCATCGGATAGCG
GGGTCTCTACAGTGCAGGGG
TAGGAATGTGGCGATGATGG
TAAACCCCACCTTCTGCTGG
AGACCGTCAATGGGTCAAGG
TGCACTAGAGCACACGTCCC
GGCATACTCTGCAGCTCACG
GACTCCATCAGCACCAAGAGC
ACTCCAACACACCCTCTCCC
ATCCAGAGAGCAAGCAAGCC
CTTGCTTTTCTTCTCCTCTCCC
GCCCATGTACATACCAGAAAGG
AGAGAGGGGCTGAGCAGAGG
GAAGCAATTTCAGGGCATGG
TGAGCCCATTCAGAAGAAATCC
TCATGCAAAAGAGGAGCTGG
ACAAGCCACCCGTAGTCTCG
AGCTCGGCATTTTCATTTGC
AGACGAGATGAAAGCGGAGG
TCGGGTAAGTATCATCCGGC
CCAAGAAGAACAAGACCGCC
TGCCAGAGATTACATACATGCC
GGGCCTAGTTTGGTGAGAGC
GGCGTAGGACATCAGTTCCC
GATCGAAAAGGTTGCTTAACG
TTGGGCTTAACTGGTGATTGG
TTAGGTGGTCGAGTGGAGGG
GAAAACGTTGTGCCCAATCC
AAATTCTTTTAAGCACTGGGAAGC
CATTCTTCCTGCCAACACCC
GAATACGAATCCTCCAACAGCC
AAGTCCAAAGCAGCCCTCC
AAGTTGATTGCACGTCCTCG
GCGTCCTTGTTAATGTGCGG
CTTTTGTCCTGCAAACACCC
CAGGAGACTTGGTGCATTGG
GACTCGCTTCTCACCGTTCC
AGCTCGTCAACCTTCATGGG
TTACAGCAAATTCGGCAAGC
GAAGACGGCAGCAAAGAACC
ATCTCTCCGTGAGTGCCAGC
CTGCTGGAGAGGCTTTGAGG
GAAGACGACAGTGAAAGGCG
AGCCTCTCTCACAAGCCAGC
ATTCCGACACTCCTTGTTGC
TCAGGCATTAAACAGCCTCG
TCAGCAGAGACAAGGCTTCG
TGTTTGTGTTTCGGTCTGGC
AATGGCTCAGGTTCTGCTGG
ACTCGCCAAAATGAATCACG
GACAGATCCCTTGGTCCTGC
CACAGGTCGTTCGAGTGCC
AAGCTGGCTGCTCAAGTTACG
CATTGATGGCGACTTTCAGC
AACCACGCCAAAAGACAAGG
CGTATGGGCTGTGAGAGACG
CGGTGTCCTCAAGACCTTCC
TCCAAAGATGATGACTGGCG
TGGTCAACACAGCACCAGC
AGCTGCTCTGATACCTGGGG
60
AC(16)
AT(18)
TC(18)
AT(14)
AT(18)
AC(26)
TC(18)
AC(22)
TC(14)
AT(12)
AC(12)
AC(12)
TC(14)
AC(14)
AC(12)
CG(12)
TC(22)
AC(12)
AC(16)
AC(12)
TC(14)
AC(12)
AC(12)
TC(18)
CG(16)
AC(16)
TC(14)
AC(14)
AC(22)
AC(12)
TC(12)
AC(12)
TC(14)
AC(12)
TC(12)
TC(12)
AC(12)
AT(14)
107
CATCGCATGATGTTTTCACG
108
109
AAACCGGGTGTTGGGAGG
AAATACTCCCCACACACCCC
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
GCTTCTGGGAAGAAAGCTCC
TTGTACGATGGCCTCTCTCG
AGACAAGCCATTGTTTGGGG
CTCATGCATTGAACAAGCCC
GATCCAGTCCTGCATAGGGC
GACGCGTTAGCTGGAGAAGG
CGTGAACATCACCACCAACC
AAAGTTCATTCATGACGGCG
TTTGTCTGTGATTACTGCTGCG
AAAATCCAATCCCCTGTCCC
CTGGAACTCTGACGCGACC
GTTGGATTGCATTTGTTCGC
GATCCAGTCCTGCATTGGG
CTTCTCTCGCTGCGTCTTGG
GCATCTGCGAAATGAACAGC
TCAGCTGCTGTCTCTTTGCC
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
CCTGAGATCATGACCTGGACC
CAACATCCCCAGATCTCTCTCC
GGCTGTTAGAGATGAGCCACG
TTTGAGGAGCGAGAAATGGC
GGTTCCCTTTACCCCTCACC
GATCTGTCATCGGTGGATGG
GATTAAGTACTGCCTGTGTCTCT
GC
AACATCAACAACCCAGGAACG
ACAGACGAGGACGACACAGG
TCCACAATTCGCCAGTTCG
TCATGTCCGAACAGCATCG
ATGGTGGCATAGACAAAGCG
GCTTAGCCGGACAGTTTTGG
CGTAGGATGGAGAGAAGGCG
TGTATCTCGGCGATTTGTCG
141
TCGTCATGTCTGTCAGCCG
AGAGGTTTAAATATTACTCCTCCG
C
GACAAGGATGAGCGACCAGC
TCATACTTGTTTCTTTATTCCTGTT
GC
CTTGAGATCAGCCTAGGGGC
AGAGGGATGAAACAGAGCCG
CTGCTTTTCCCACCATAGCC
ACGGAACCAACAGATGGACG
CTTCCATTGGGCATGTCTGG
ATCCCCACGGACAGGAGG
TTTGTTCCAGCAGCTTCACG
GGAGAAAGTGAGCAGTGGGG
TTTTCGAATGAAAGTCGACCC
AGCACTTCTCCATTGCTCCC
ATCTGGATGCTTTTCCGTGG
AAGTAGCGATTGTCCCGAGC
TTGAAAGAGACAGGATTTGAGTGC
CTCGTCGTACTTGGCACTGG
TATCAAGAGCGGTGTGACGG
CACACAAAGGAACTTTATTTAGTT
TTGC
TGCTAATTTTGTGTCCTCTGTGG
TGGTGAAGATGTGCAAAGACG
TAAAGAAGGGACTGCCACGC
CGAACTGCAATGACTCCAGG
CGGACTGGAAAGTTGAACTGC
CAGACTGGATTCGCTCATGC
GATCAGCTGGGAGCCTGC
AT(12)
TTGTCACCCACGACTCTTCG
GAGTTCATCGCAAGCTACGC
TGCTTACGCTTGGTCTTTGC
ACCTGTTCATCCTGGGTTGG
ATGGCTACATCACTGGTGCG
TCCGGTTCTTACAATTGGGC
GGACGAGTTTTGTCACCTCG
CGATGAATAGAGCCATGTAGAATG
C
TGTAGTCGTTGATGTCGGTGC
AC(26)
TC(12)
CG(12)
AC(12)
TC(18)
TC(12)
TC(16)
AC(34)
61
TC(12)
TC(12)
AT(12)
TC(16)
AT(12)
TC(14)
TC(12)
TC(24)
AC(12)
TC(12)
AT(12)
AC(14)
TC(18)
TC(12)
TC(14)
CG(12)
AT(16)
AT(16)
TC(18)
AC(26)
TC(12)
AT(18)
AT(16)
AC(12)
TC(32)
AC(12)
142
143
144
145
146
ACGGTTTGTAAGTGCGGAGC
CACCGAGACTCTGAACTGAGC
ATTCCTGCCACATGAAAGCC
GACGATGGCGATGTATCTGG
CTCGAGTCCAATCTCCTGCC
147
148
149
150
151
TATTCAGGTCCGACACACGC
AAGAAAAGCCCCTACCACGC
TTGCAGTGAGCACTGTTTGC
CATATGCGACATAGGAGGAGC
TGAAGAGACTAGATATGCAAGG
GC
GAACCCAAGGCTCAGAGAGG
152
CAGAGACGACCCATCTGTGG
TGCAGCAAGAGAAATCTTCACC
GTGTGAGGTCTGGACTCCCC
GGTGTTTTGGGCTTGCTAGG
GAGAGAAATGGTGGAGAAAAGAC
C
TGCGAATTGCTATGACAGGG
GAGCCGAGCTCTTTGTACCG
GAGAGCGGTCTACGCATGG
TGTGTTTGTGTGCAAATACTACG
GGCACTAAGAAAGCAGTAGGGG
TC(12)
AC(12)
AC(14)
TC(12)
AC(12)
TGCAGGAGTCTGCTTCTCCC
TC(16)
62
TC(24)
AC(28)
TC(20)
AC(12)
AC(12)
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