Ecological Interactions

For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna.

Aquatic plants fulfil a wide range of ecological roles, and make a substantial contribution to the structure, function and service provision of aquatic ecosystems. Given their well-documented importance in aquatic ecosystems, research into aquatic plants continues to blossom. The 14th International Symposium on Aquatic Plants, held in Edinburgh in September 2015, brought together 120 delegates from 28 countries and six continents. This special issue of Hydrobiologia includes a select number of papers on aspects of aquatic plants, covering a wide range of species, systems and issues. In this paper, we present an overview of current trends and future directions in aquatic plant research in the early twenty first century. Our understanding of aquatic plant biology, the range of scientific issues being addressed and the range of techniques available to researchers have all arguably never been greater; however, substantial challenges exist to the conservation and management of both aquatic plants and the ecosystems in which they are found. The range of countries and continents represented by conference delegates and authors of papers in the special issue illustrates the global relevance of aquatic plant research in the early twenty first century but also the many challenges that this burgeoning scientific discipline must address.

True agriculture-defined by habitual planting, cultivation, harvesting and dependence of a farmer on a crop-is known from fungi farmed by ants, termites or beetles, and plants farmed by humans or ants. Because farmers supply their crops with nutrients, they have the potential to modify crop nutrition over evolutionary time. Here we test this hypothesis in ant/plant farming symbioses. We used field experiments, phylogenetic-comparative analyses and computed-tomography scanning to investigate how the evolution of farming by ants has impacted the nutrition of locally coexisting species in the epiphytic genus Squamellaria (Rubiaceae). Using isotope-labelled mineral and organic nitrogen, we show that specialised ants actively and exclusively fertilise hyperabsorptive warts on the inner walls of plant-formed structures (domatia) where they nest, sharply contrasting with nitrogen provisioning by ants in nonfarm-ing generalist symbioses. Similar hyperabsorptive warts have evolved repeatedly in lineages colonised by farming ants. Our study supports the idea that millions of years of ant agriculture have remodelled plant physiology, shifting from ant-derived nutrients as by-products to active and targeted fertilisa-tion on hyperabsorptive sites. The increased efficiency of ant-derived nutrient provisioning appears to stem from a combination of farming ant behaviour and plant 'crop' traits.

A diversity of macro-and microparasitic species exert strong influences on wildlife population density, community structure, and ecosystem functioning, all through their impacts on individual host fitness. Through consuming, manipulating, and relocating wildlife feces, over 7,000 species of coprophagous dung beetles interact with a staggering diversity of wildlife parasites with fecal-oral transmission in ways that both increase and decrease transmission. Here, we review the mechanisms by which dung beetles influence micro-and macroparasite transmission and outline a future research framework that integrates theory and empirical insights to advance our understanding of how these relationships may interact with ongoing environmental change drivers to further influence wildlife populations and community structure. Any organism that significantly influences parasite transmission will impact multiple levels of biological organization. Therefore, improving our understanding of the role of dung beetle interactions within disease ecology will be key to future efforts to understand the overall dynamics of infection in wildlife and how parasites contribute to the maintenance of ecosystem structure and function and evolutionary processes in wild animals.

Neotropical frugivorous bats display a trophic structure composed of bat species with dietary preferences of core plant taxa (Artibeus-Ficus + Cecropia, Carollia-Piper, Sturnira-Solanum + Piper). This structure is hypothesized to be an ancestral trait, suggesting that similar diets would be observed throughout a species' range. However, most evidence comes from lowlands where data from montane habitats are scarce. In high mountain environments both diversity of bats and plants decreases with altitude; such decline in plant diversity produces less plants to feed from, which should ultimately affect the trophic structure of frugivorous bats in mountain environments. Here, we present a comprehensive review of the diet of frugivorous bats in Neotropical montane environments and evaluate their trophic structure in middle and higher elevations by combining a literature database with field data. We use the concept of modularity to test whether frugivorous montane bats have dietary preferences on core plant taxa. Our database revealed 47 species of montane bats feeding on 211 plant species. We find that the networks are modular, reflecting the trophic structure previously reported. We also found that in highlands the tribe Ectophyllini are Cecropia + Cavendishia-specialists rather than Ficus-specialists, and we describe new interactions reflecting 14 species of plants, including three botanical families previously not reported to be consumed by bats.

Vanilla palmarum is an obligately epiphytic orchid distributed widely throughout South America with emblematic specificity for species of palms. This epiphyte-phorophyte association was examined through the analysis of specimens available via the database of Centro de Referência em Informação Ambiental and from Brazilian herbaria. We recognized nine species as hosts of V. palmarum in Brazil: Acrocomia aculeata, Attalea phalerata, Attalea speciosa, Elaeis guineensis, Mauritia flexuosa, Syagrus cearensis, S. coronata, S. schizophylla, and S. vagans. The most important phorophytes of V. palmarum were found to be A. speciosa (Cerrado), A. phalerata (Pantanal), M. flexuosa (Amazon Forest) and S. coronata (Caatinga). Future management actions must consider the association between V. palmarum and its phorophyte palm species in order to ensure the protection of this ecological interaction. Resumo Vanilla palmarum (Orchidaceae) é uma holoepífita obrigatória, amplamente distribuída na América do Sul, e apresenta uma emblemática especificidade com palmeiras. A interação epífita-forófitos foi examinada através da análise de espécimes disponíveis na base de dados do Centro de Referência em Informação Ambiental e em herbários brasileiros. Nós reconhecemos nove espécies hospedeiras de V. palmarum no Brasil: Acrocomia aculeata, Attalea phalerata, Attalea speciosa, Elaeis guineensis, Mauritia flexuosa, Syagrus cearensis, S. coronata, S. schizophylla e S. vagans. Os principais forófitos de V. palmarum são: A. speciosa (Cerrado), A. phalerata (Pantanal), M. flexuosa (Floresta Amazônica) e S. coronata (Caatinga). As futuras ações de manejo devem considerar a associação entre V. palmarum e espécies de palmeiras, visando assegurar a proteção das interações ecológicas. Palavras-chave: coleções botânicas, interações ecológicas, endemismos, orquídea, domínios fitogeográficos.

Las interacciones ecológicas ocurren en todo el planeta y son vitales para el funcionamiento adecuado de los ecosistemas. Pueden ser sencillas, de especie a especie, o bien, integrar un ecosistema entero (interacciones multitróficas). El estudio de las interacciones contribuye al conocimiento de la naturaleza y brinda herramientas para temas de conservación de los sistemas naturales.

Apex predators play an important role in regulating ecological interactions, and therefore their loss can affect biodiversity across trophic levels. Large carnivores have experienced substantial population and range declines across Africa, and future climate change is likely to amplify these threats. Hence it is important to understand how future environmental changes will affect their long-term habitat suitability and population persistence. This study aims to identify the factors limiting the distribution of the endangered African wild dog, Lycaon pictus, and determine how biotic interactions and changing climate and land cover will affect future range suitability. We use Species Distribution Models (SDMs) to predict the current and future distribution of suitable conditions for L. pictus and its dominant competitor Panthera leo . We show that range suitability for L. pictus is limited by climatic and land cover variables, as well as high niche and range overlap with P. leo . Alth...

Aggressive behavioural interactions between animals are widespread in nature, with ecological and evolutionary consequences of such interactions reported for both individuals giving and receiving aggression. Yet despite the importance of aggressive interactions in determining social dominance and conferring fitness benefits to successful individuals, we lack a general understanding of the conditions that influence the variation in agonistic behaviours among individuals and species. We conducted a global meta-analysis of published time-activity budgets, using a data set comprising 555 values from 88 studies, to determine variation in the time that waterbirds engaged in aggressive interactions. The mean ± SD percentage of time devoted to aggression was 2.0 ± 3.6%, with a range of 0.0-35.0%. We used our data set to test four predictions regarding avian aggression, based on the findings of earlier site-based studies. We predicted that the time spent on aggression would be influenced by four factors: (1) age class, (2) sex, (3) seasonal timing and (4) functional feeding group. A comparison of linear mixed-effects models using an information theoretic approach indicated that the proportion of time waterbirds spent engaged in aggressive interactions was best explained by the age class and sex of the focal waterbird species. More time was spent on aggression by males than females, and by adults than juveniles. We found no evidence that the time spent on aggressive behaviours varied across latitudes or body mass, with seasonal timing, sexual dimorphism, migration or breeding strategies, or between different functional feeding groups. Our findings highlight the high levels of variation in the time devoted to aggression across species, feeding groups, latitudes and seasons. Furthermore, our study demonstrates the utility of the numerous published time-activity budget studies that are available as a valuable source of data that can be used to answer broad-scale questions regarding animal behaviour.

Premise of the study: Plant–herbivore networks are highly specialized in their interactions, yet they are highly variable with regard to the relative importance of specific host species for herbivores. How host species traits determine specialization and species strength in this antagonistic network is still an unanswered question that we addressed in this study.

Methods: We assessed plant cover and anti-herbivore resistance traits to assess the extent to which they accounted for the variation in specialization and strength of interactions among species in a plant–herbivore network. We studied a tropical antagonistic network including a diverse herbivore–host plant assemblages in different habitat types and climatic seasons, including host plants with different life histories.

Key results: Particular combinations of leaf toughness, trichome density, and phenolic compounds influenced herbivore specialization and host species strength, but with a significant spatiotemporal variation among plant life histories. Conversely, plant–herbivore network variables were not influenced by plant cover.

Conclusions: Our study highlights the importance of species-specific resistance traits of plants to understand the ecological and evolutionary consequences of plant–herbivore interaction networks. The novelty of our research lies in the use of a trait-based approach to understand the variation observed in diverse plant–herbivore networks.

Key words: plant–herbivore interactions; antagonistic networks; plant resistance traits; host plant cover; specialization; species strength

American Journal of Botany__ Article in Press · August  2016

Plant development is influenced by several abiotic factors, which in turn influence morphological traits and life history. We investigated whether leaf area, herbivory, toughness, fluctuating asymmetry, structural complexity and the number of inflorescences of Palicourea rigida are influenced by sun/shade conditions or by Cerrado phytophysiognomy (typical cerrado or rupestrian field). We expected to find greater structural complexity, leaf toughness and more inflorescences in sun plants; shaded plants were expected to exhibit a greater degree of fluctuating asymmetry (an index of plant stress), reduced leaf toughness and greater herbivory. As for phytophysiognomies, we expected to find higher levels of leaf toughness and reduced structural complexity in plants from the rupestrian field. We sampled plants in the sun and shade from both phytophysiognomies. Leaf area, toughness, herbivory and fluctuating asymmetry, were influenced more by sun/shade conditions than phytophysiognomy; leaf toughness was the only variable to show greater values in conditions of sun. Our results indicate that exposure to sunlight is not a requirement for increased plant development, but plants in shade are experiencing stress, as shown by increased fluctuating asymmetry; increased leaf area, which is a strategy to compensate for lower light exposure for plants and higher herbivory, which depicts lower toughness.

For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary bene...

Anthropogenic modification of natural environments is the main causes of species extinction in the globe, which directly leads to loss of interspecific links and modifies the structure of ecological networks. The objective of present study is to evaluate the effect of human-induced habitat modification on the connectivity and robustness of ecological interaction networks composed by plant-epiphyte and plant-parasite interactions. In total were analyzed eight distinct binary networks of plant-plant interactions in Brazil, being three epiphyte networks and five parasite networks occurring both in conserved and anthropized habitats. The results show that the human-induced habitat modification influences the connectance of plant-plant networks, since networks of anthropized habitats had greater connectance than the networks of conserved habitats. In addition, the results showed higher values of robustness in the plant-parasite networks when compared to plant-epiphyte networks, and these differences were mainly observed in anthropized habitats. This study presented a new approach for studies of plant-plant ecological interactions, because is the first to compare the effect of human-induced habitat modification on the plant-plant network robustness.

By noting the spatial location of captured individuals mark-recapture studies create a collection of discrete events spread in space and time. This setup is appropriate for network modeling where the vertices (or nodes) are the points of capture and links are established whenever a recapture occurs. Applying network analytical tools, it is possible to ascertain aspects of spatial structure and generate predictions regarding the likely causes of structure in the network. We studied the spatial network of two tropical butterfly species, Heliconius erato and H. melpomene, using a mark-recapture database from a 2-year survey in an Atlantic Forest remnant in Brazil. The overall network structure of both species was similar in number of vertices and average connectivity. Heliconius erato had a smaller, more disconnected network structure, suggesting shorter traveling paths. The distribution of connectivity of both species was better adjusted by a power-law distribution. We found hubs in both species; hubs are points of high capture and their location is correlated with the location of flowering plants visited by adults. In complex systems, hub elimination can have a notable collapsing effect in network structure. Because resource hubs are important for butterfly network organization we suggest management as well as experimental tests with regards to the role of resource hotspots for population structure.

Understanding the patterns and processes behind the high biological diversity of tropical ecosystems has been one of the most important issues in modern ecology. Plant-herbivore interactions constitute an important percentage of biodiversity in the tropics, and their ecological and evolutionary importance has been demonstrated in a large number of studies. However, it is only very recently that plant-herbivore antagonistic interactions are being addressed from the perspective of complex networks to evaluate how different factors influence their interaction patterns. In this chapter, we provide a summary of the processes that have been reported shaping the specialization and structuring of tropical plant-herbivore networks. From the limited availability of studies in such habitats we suggest that plant-herbivore networks are spatio-temporally dynamic, and are the result of multiple non-exclusive processes where seasonality, variation in resource availability, type and disturbance of habitat and species-specific attributes contribute to structuring these highly diverse and specialized antagonistic networks.

Functional traits can be used to identify various ecosystem processes that are influenced by natural and anthropogenic factors. We tested the hypothesis that the species composition and functional feeding traits of zooplankton are influenced by environmental gradients, such as depth, trophic status, and ion content. This hypothesis was tested in three lignite strip mine lakes in Central Poland. Two shallow, polymictic lakes were reclaimed (1994 and 2008), and the third deep, stratified lake has been reclaimed during the flooding process, since 2011. Samples were collected monthly in 2016 and 2017. The functional responses of zooplankton communities to environmental variables were tested through redundancy analyses. Both eutrophy and oligotrophy contributed to the taxonomic heterogeneity and functional homogeneity of zooplankton. In eutrophic condition small microphagous rotifers and small-sized crustaceans dominated, while oligotrophy and high ion concentrations favored dominance of...

Understanding the patterns and processes behind the high biological diversity of tropical ecosystems has been one of the most important issues in modern ecology. Plant-herbivore interactions constitute an important percentage of biodiversity in the tropics, and their ecological and evolutionary importance has been demonstrated in a large number of studies. However, it is only very recently that plant-herbivore antagonistic interactions are being addressed from the perspective of complex networks to evaluate how different factors influence their interaction patterns. In this chapter, we provide a summary of the processes that have been reported shaping the specialization and structuring of tropical plant-herbivore networks. From the limited availability of studies in such habitats we suggest that plant-herbivore networks are spatiotemporally dynamic and are the result of multiple non-exclusive processes where seasonality, variation in resource availability, habitat type, disturbance regime and species-specific attributes contribute to structuring these highly diverse and specialized antagonistic networks.

Apex predators play an important role in regulating ecological interactions, and therefore their loss can affect biodiversity across trophic levels. Large carnivores have experienced substantial population and range declines across Africa, and future climate change is likely to amplify these threats. Hence it is important to understand how future environmental changes will affect their long-term habitat suitability and population persistence. This study aims to identify the factors limiting the distribution of the endangered African wild dog, Lycaon pictus, and determine how biotic interactions and changing climate and land cover will affect future range suitability. We use Species Distribution Models (SDMs) to predict the current and future distribution of suitable conditions for L. pictus and its dominant competitor Panthera leo. We show that range suitability for L. pictus is limited by climatic and land cover variables, as well as high niche and range overlap with P. leo. Althou...

Este estudo teve como objetivo um levantamento do conhecimento que os indígenas Kayabi possuem sobre a avifauna de ocorrência natural na Terra Indígena Kayabi, localizada na Amazônia, entre os estados do Pará e Mato Grosso, Brasil. Para coleta de dados foram realizadas entrevistas com vinte e dois indígenas que citaram 165 espécies de aves e mostraram amplo conhecimento ecológico sobre estas aves, incluindo categorias relacionadas à morfologia, hábitos alimentares, hábitats e vocalização.

Kleptoparasitism involves the theft of resources such as food items from one individual by another. Such food-stealing behaviour can have important consequences for birds, in terms of individual fitness and population sizes. In order to understand avian host-kleptoparasite interactions, studies are needed which identify the factors which modulate the risk of kleptoparasitism. In temperate European intertidal areas, Eurasian oystercatchers (Haematopus ostralegus) feed primarily on bivalve molluscs, which may be stolen by kleptoparasitic species such as carrion crows (Corvus corone) and herring gulls (Larus argentatus). In this study we combined overwinter foraging observations of oystercatchers and their kleptoparasites on the Exe Estuary, UK, with statistical modelling to identify the factors that influence the likelihood of successful food stealing behaviour occurring. Across the winter, 16.4 % of oystercatcher foraging attempts ended in successful kleptoparasitism; the risk of theft was lowest in February (10.8 %) and highest in December (36.3 %). Using an information theoretic approach to compare multiple logistic regression models we present evidence that the outcome of host foraging attempts varied with the number of kleptoparasites per host within the foraging patch for two out of five individual months, and for all months grouped. Successful, kleptoparasitism was more likely to occur when the total number of all kleptoparasites per host was greater. Across the entire winter study period, oystercatcher foraging attempts that resulted in kleptoparasitism were associated with a mean number of kleptoparasites per host that was more than double that for foraging attempts that ended in the oystercatcher successfully consuming the mussel. Conversely, the stage of the tidal cycle within the estuary did not affect the outcome of oystercatcher foraging attempts. Our study provides evidence that bird numbers influence the risk of kleptoparasitism within avian assemblages.

The Moraceae family has been the theme of several ecological aproaches, their anatomy and phenology features provide a variety of interactions with wildlife, and relevant studies have highlighted the Ficus genus as an important source of food and resting resource for some animal species. The aim of the study was to investigate feeding interactions between the fig trees and animals, both the residents and the visitors at Parque Centenário in Barra Mansa south of Rio de Janeiro state. The study was carried out from August 2009 to July 2010 and the data collection involved observations of  14  fig trees in the area. Were considered target species birds and mammals that fed on any tree item, including the some fallen on the ground. On 56 sessions of observation, 12 species of birds have been recorded:  Rufous-bellied thrush (Turdus rufiventris Vieillot, 1818), Creamy-bellied Thrush (Turdus amaurochalinus Cabanis, 1850) , Sayaca Tanager (Thraupis sayaca Linnaeus, 1766) ,  Ruddy ground dove (Columbina talpacoti Temminck, 1810), Great Kiskadee (Pitangus sulphuratus Linnaeus, 1766), Green-barred Woodpecker(Colaptes melanochloros, Gmelin, 1788), Tropical Kingbird (Tyrannus melancholicus Vieillot, 1819),  White-rumped Monjita (Xolmis velatus
(Lichtenstein, 1823), Grey-fronted Dove (Leptotila rufaxilla Richard & Bernard, 1792),  Burnished-buff Tanager (Tangara cayana,  Linnaeus, 1766) and  Brazilian tanager (Ramphocelus bresilius Linnaeus, 1766). We also recorded the foraging tactics and potential spreader of which are highlighted as potentially more dispersers: T. rufiventris, T. amaurochalinus and T. sayaca. Among resident mammals were found two species introduced in the park, the  Brown-throated Three-toed Sloth (Bradypus variegatus Schinz, 1825) which eat leaves, shoots and figs and the Red-rumped agouti (Dasyprocta agouti Linnaeus, 1766 ) that despite being feed by the keepers, supplement their diet with figs fallen. The  Ficus species are an important food source for birds and mammals residents and also for those visitors the park area, possibly due to their asynchrony for flowering and fruiting, providing food all over the year.

The overgrowth of octocorals by sponges is generally disadvantageous for the octocorals. When
the growth of octocoral populations increases the reefs’ structural complexity, more substrate
space becomes available for epibionts to grow. One of these epibionts is the sponge Desmapsamma
anchorata, known to grow exponentially faster than other sponges, and for its ability to overwhelm
the substrate over which it grows. Our objective in this study is to determine if the overgrowth
of branching octocorals by varying sponges is defined only by species-specific interactions,
or if some physical attributes make this octocoral more susceptible to being overgrown than others.
To determine this, on a reef south of Carrie Bow Cay, Belize, we monitored the attachment of various
demosponges to branching octocorals in a series of experiments to assess the response effect
of the interactions and properties leading to attachment and subsequent sponge overgrowth on
branching octocorals. Substrate effects, species-specific reactions, and time of exposure were considered.
Additionally, following successful-attachment, preliminary growth rates of two sponge
species epizoic on two octocoral species were monitored. Differences in the observed interaction
between species and treatments were analyzed with a multinomial response model to isolate a
species-specific effect from other interacting effects of the properties tested. Results indicate that
time of exposure of a sponge in direct contact with the octocoral fragment significantly affects the
outcome of the interaction; secondly, physical properties and species-specific interactions also influence
the attachment. Following the successful attachment to an octocoral, the growth of the
sponge varies as a function of the sponge’s differential growth rate and the substrate species over
which it grows. In the context of species successions, understanding interactions between coralreef
organisms is important as these interactions explain species composition and diversity, and
provide a basis for the prediction of future changes in complex reef communities.