molecular genetics to gain insight into allopatric and sympatric speciation of topshells and thei... more molecular genetics to gain insight into allopatric and sympatric speciation of topshells and their parasitic trematodes
We have used the DNA sequences of Pacific topshells, belonging to the genera Diloma, Melagraphia ... more We have used the DNA sequences of Pacific topshells, belonging to the genera Diloma, Melagraphia and Austrocochlea, to ascertain how this group became established over a large area of the Pacific. Phylogenetic analyses of three genes revealed that Pacific topshell species belong to three major clades. The first two clades, including the most basal clade, consisted solely of Australian Austrocochlea species. The third clade contained the remainder of the Pacific species, representing all three genera, collected from sites in Australia, New Zealand, Chile, Samoa and Japan. Studying these molecular phylogenies, in conjunction with information available on the fossil record of this group and their life history, allowed us to explain how their Pacific wide dispersal evolved. Our results suggest that there were initially two dispersal events from Australia: a northeastward dispersal to an area stretching from Samoa to Japan and an eastward dispersal to New Zealand. From New Zealand there ...
Prevailing theory suggests that many parasite species have evolved in tight congruence with their... more Prevailing theory suggests that many parasite species have evolved in tight congruence with their hosts, with the parasite phylogeny mirroring that of the host. This theory is based largely on studies of host-parasite interactions between species where strong links would be expected. For example, the highly congruent evolutionary trees of procellariform seabirds and their feather lice (Paterson et al., 1993) are expected as oceanic seabirds breed in large, often monospecific, colonies and lice do not survive long away from their host. Consequently, in this case, there are few opportunities for host switching. Our research employs molecular techniques to test the theory of tight host-parasite congruence in a host-parasite system where high host specificity is not necessarily expected; Trochoidea (topshell snails) and digenean trematodes (flatworms). Due to the fine-scale sympatry of the topshell hosts and the complex life cycle of digeneans, the parasites are likely to encounter a ra...
We examined phylogeographic structure in the direct-developing New Zealand endemic intertidal mud... more We examined phylogeographic structure in the direct-developing New Zealand endemic intertidal mud whelk, Cominella glandiformis. Two hundred and ninety-six whelks from 12 sites were collected from sheltered shores around New Zealand’s four largest islands (North Island, South Island, Stewart Island and Chatham Island), encompassing the geographical range of this species. Despite being direct developers, gene flow among C. glandiformis populations may occur over short distances by adult floating, and over larger distances by rafting of egg masses. Primers were developed to amplify variable microsatellite regions at six loci. All loci were variable, with 8–34 alleles/loci. Observed and expected heterozygosities were high across all alleles, with minimal evidence of null alleles. The average number of alleles varied from 3.5 (Chatham Island) to 7.5 (Waitemata Harbour). Strong genetic structure was evident, with distinct ‘eastern’ and ‘western’ groups. Each group extended over a large g...
Digenean parasites infecting four Cominella whelk species (C. glandiformis, C. adspersa, C. macul... more Digenean parasites infecting four Cominella whelk species (C. glandiformis, C. adspersa, C. maculosa and C. virgata), which inhabit New Zealand's intertidal zone, were analysed using molecular techniques. Mitochondrial 16S and cytochrome oxidase 1 (COI) and nuclear rDNA ITS1 sequences were used to infer phylogenetic relationships amongst digenea. Host species were parasitized by a diverse range of digenea (Platyhelminthes, Trematoda), representing seven families: Echinostomatidae, Opecoelidae, Microphallidae, Strigeidae and three, as yet, undetermined families A, B and C. Each parasite family infected between one and three host whelk species, and infection levels were typically low (average infection rates ranged from 1·4 to 3·6%). Host specificity ranged from highly species-specific amongst the echinostomes, which were only ever observed infecting C. glandiformis, to the more generalist opecoelids and strigeids, which were capable of infecting three out of four of the Cominella...
Current taxonomic treatments of New Zealand and temperate Australian members of the gastropod sub... more Current taxonomic treatments of New Zealand and temperate Australian members of the gastropod subfamily Cantharidinae imply that species on either side of the Tasman Sea are closely related and, in some cases, congeneric. Such a close relationship, however, entails a relatively recent divergence of Australian and New Zealand lineages, which seems inconsistent with what is known about cantharidine larval development in general. In order to address these issues, mitochondrial and nuclear DNA sequences were used to ascertain how cantharidine genera became established over the wide geographical range of temperate Australia and New Zealand, including their subantarctic islands. Our robust and dated phylogenies (based on 16S, COI, 12S and 28S sequences) revealed that Australian and New Zealand species fall into endemic clades that have been separated for, at most, 35million years. This divergence date postdates a vicariant split by around 50million years and we suggest that, once again, long-distance trans-Tasman dispersal has played a pivotal role in molluscan evolution in this part of the world. Our results also show that the current classification requires revision. We recognize three genera (Cantharidus [comprising 2 subgenera: Cantharidus s.str. and Pseudomargarella n. subgen.], Micrelenchus [comprising 2 subgenera: Micrelenchus s.str. and Mawhero] and Roseaplagis n. gen.) for New Zealand cantharidine species. In our dated BEAST tree, these genera form a clade with the endemic Australian Prothalotia and South African Oxystele. Other temperate Australian cantharidines in our study fall into previously recognized genera (Phasianotrochus, Thalotia, Calthalotia), which are all quite distinct from Cantharidus in spite of some authors considering various of them to be possible synonyms. Finally, we remove the Australian genus Cantharidella from the Cantharidinae to the subfamily Trochinae and erect a new genus, Cratidentium n. gen., also in the Trochinae, to accommodate several Australian species previously considered to belong to Cantharidella.
In the marine cyanobacterium Synechococcus sp. strain WH7803, PstS is a 32-kDa cell wall-associat... more In the marine cyanobacterium Synechococcus sp. strain WH7803, PstS is a 32-kDa cell wall-associated phosphate-binding protein specifically synthesized under conditions of restricted inorganic phosphate (P1) availability (D. J. Scanlan, N. H. Mann, and N. G. Carr, Mol. Microbiol. 10:181-191, 1993). We have assessed its use as a potential diagnostic marker for the P status of photosynthetic picoplankton. Expression of PstS in Synechococcus sp. strain WH7803 was observed when the P1 concentration fell below 50 nM, demonstrating that the protein is induced at concentrations of P1 typical of oligotrophic conditions. PstS expression could be specifically detected by use of standard Western blotting (immunoblotting) techniques in natural mesocosm samples under conditions in which the N/P ratio was artificially manipulated to force P depletion. In addition, we have developed an immunofluorescence assay that can detect PstS expression in single Synechococcus cells both in laboratory cultures...
ABSTRACT The turritellid Maoricolpus roseus (Quoy & Gaimard, 1834) is abundant in low int... more ABSTRACT The turritellid Maoricolpus roseus (Quoy & Gaimard, 1834) is abundant in low intertidal and shallow water marine environments around the coasts of New Zealand. It is currently divided into two regional subspecies: M. roseus roseus, common around much of New Zealand’s coast; and M. roseus manukauensis, restricted to several west coast harbours in the North Island, specifically Manukau, Raglan and Kawhia. Molecular data, consisting of both mitochondrial (16S rRNA and cytochrome oxidase I (COI)) and nuclear (18S rRNA and 28S rRNA) genes, were collected and analysed to resolve the status of these subspecies. Our analyses reveal that neither subspecies is monophyletic in our phylogenetic trees, and that the genetic distances between them are no greater than those within. We thus argue that M. roseus manukauensis should be synonymised with the nominotypical subspecies. Maoricolpus roseus is a morphologically variable species, with low levels of 16S and COI genetic diversity within and among different populations.
The systematics of topshells (family Trochidae) is currently unresolved: at present even the gene... more The systematics of topshells (family Trochidae) is currently unresolved: at present even the generic boundaries within this group are poorly defined. In this study, we used sequence data of two mitochondrial genes (16S and cytochrome oxidase 1, COI) and one nuclear gene (actin) to resolve the phylogeny of a closely related subgroup of the Trochidae, 30 species of largely Southern Hemisphere monodontine topshells. The phylogenies constructed revealed five well-supported generic clades: a South African clade (genus Oxystele Philippi, 1847), which lay basally to four internal Pacific clades (genera Chlorodiloma Pilsbry, 1889; Monodonta Lamarck, 1799; Austrocochlea Fischer, 1885; and Diloma Philippi, 1845). The molecular phylogenies constructed in this study shed light on previously unresolved relationships between different groups of topshells, allowing for the first time assignation (based on DNA sequence) of clearly defined, well-supported taxonomic and nomenclatural classification of monodontine topshells species. Austrocochlea crinita (Philippi, 1849), A. odontis (Wood, 1828), A. adelaidae (Philippi, 1849), and A. millelineata (Bonnet, 1864) are placed in the genus Chlorodiloma, which we resurrect from synonymy with Austrocochlea. The Japanese M. confusa Tapparone-Canefri, 1874 is treated as a separate species from M. labio (Linné, 1758). Melagraphia Gray, 1847 is synonymised with Diloma and its sole member, M. aethiops (Gmelin, 1791), along with A. concamerata (Wood, 1828), is transferred to that genus. The Juan Fernandez endemic D. crusoeana (Pilsbry, 1889) is synonymised with D. nigerrima (Gmelin, 1791). We find that morphologically cryptic species are not necessarily close genetically.
Abstract Leucine aminopeptidase (LAP) belongs to a family of ubiquitous peptidases, with roles in... more Abstract Leucine aminopeptidase (LAP) belongs to a family of ubiquitous peptidases, with roles in growth and development, stress responses and adaptation to changing environmental conditions. The LAP gene was sequenced from a commercially important ...
In New Zealand, a single morphotype, comprising three genetically distinct opecoelid species, inf... more In New Zealand, a single morphotype, comprising three genetically distinct opecoelid species, infects four sympatric species of trochid snails. Two species (a and b) are specific to Diloma subrostrata while the third (c) is more general, capable of infecting three species, most commonly D. aethiops but never D. subrostrata. We sampled three D. subrostrata and D. aethiops populations, in which infection levels ranged from 0 to 29.2%, and attempted species assignation based on host information, restriction fragment length polymorphism (RFLP) analysis and morphology. Host information allowed reliable separation of species a and b from species c. Restriction mapping of ribosomal DNA internal transcriber spacer 2 (ITS2) demonstrated that the restriction enzyme SfuI only digested ITS2 from species b and c. Thus, restriction digests + host species information allowed reliable species assignation. Morphological measurements were taken for both sporocysts and cercariae dissected from 83 infected snails. Substantial overlap existed between measurements for the three species, and discriminant analysis showed that parasites could not be unequivocally assigned to a species--error rates ranged from 9 to 58%--despite statistically significant differences among several means. Amongst this group of digeneans, host information + RFLP provide a rapid, unambiguous method of species assignation that host information + morphological measurements cannot.
Journal of Experimental Marine Biology and Ecology, 2011
This study of population structure of two intertidal monodontine species: Diloma nigerrima and Di... more This study of population structure of two intertidal monodontine species: Diloma nigerrima and Diloma subrostrata, revealed the level of genetic connectedness among populations. Despite their markedly different geographic ranges (D. nigerrima is a geographically widespread species, inhabiting both Chile and New Zealand, including its subantarctic islands, whereas D. subrostrata is endemic to New Zealand), both species are believed to possess
molecular genetics to gain insight into allopatric and sympatric speciation of topshells and thei... more molecular genetics to gain insight into allopatric and sympatric speciation of topshells and their parasitic trematodes
We have used the DNA sequences of Pacific topshells, belonging to the genera Diloma, Melagraphia ... more We have used the DNA sequences of Pacific topshells, belonging to the genera Diloma, Melagraphia and Austrocochlea, to ascertain how this group became established over a large area of the Pacific. Phylogenetic analyses of three genes revealed that Pacific topshell species belong to three major clades. The first two clades, including the most basal clade, consisted solely of Australian Austrocochlea species. The third clade contained the remainder of the Pacific species, representing all three genera, collected from sites in Australia, New Zealand, Chile, Samoa and Japan. Studying these molecular phylogenies, in conjunction with information available on the fossil record of this group and their life history, allowed us to explain how their Pacific wide dispersal evolved. Our results suggest that there were initially two dispersal events from Australia: a northeastward dispersal to an area stretching from Samoa to Japan and an eastward dispersal to New Zealand. From New Zealand there ...
Prevailing theory suggests that many parasite species have evolved in tight congruence with their... more Prevailing theory suggests that many parasite species have evolved in tight congruence with their hosts, with the parasite phylogeny mirroring that of the host. This theory is based largely on studies of host-parasite interactions between species where strong links would be expected. For example, the highly congruent evolutionary trees of procellariform seabirds and their feather lice (Paterson et al., 1993) are expected as oceanic seabirds breed in large, often monospecific, colonies and lice do not survive long away from their host. Consequently, in this case, there are few opportunities for host switching. Our research employs molecular techniques to test the theory of tight host-parasite congruence in a host-parasite system where high host specificity is not necessarily expected; Trochoidea (topshell snails) and digenean trematodes (flatworms). Due to the fine-scale sympatry of the topshell hosts and the complex life cycle of digeneans, the parasites are likely to encounter a ra...
We examined phylogeographic structure in the direct-developing New Zealand endemic intertidal mud... more We examined phylogeographic structure in the direct-developing New Zealand endemic intertidal mud whelk, Cominella glandiformis. Two hundred and ninety-six whelks from 12 sites were collected from sheltered shores around New Zealand’s four largest islands (North Island, South Island, Stewart Island and Chatham Island), encompassing the geographical range of this species. Despite being direct developers, gene flow among C. glandiformis populations may occur over short distances by adult floating, and over larger distances by rafting of egg masses. Primers were developed to amplify variable microsatellite regions at six loci. All loci were variable, with 8–34 alleles/loci. Observed and expected heterozygosities were high across all alleles, with minimal evidence of null alleles. The average number of alleles varied from 3.5 (Chatham Island) to 7.5 (Waitemata Harbour). Strong genetic structure was evident, with distinct ‘eastern’ and ‘western’ groups. Each group extended over a large g...
Digenean parasites infecting four Cominella whelk species (C. glandiformis, C. adspersa, C. macul... more Digenean parasites infecting four Cominella whelk species (C. glandiformis, C. adspersa, C. maculosa and C. virgata), which inhabit New Zealand's intertidal zone, were analysed using molecular techniques. Mitochondrial 16S and cytochrome oxidase 1 (COI) and nuclear rDNA ITS1 sequences were used to infer phylogenetic relationships amongst digenea. Host species were parasitized by a diverse range of digenea (Platyhelminthes, Trematoda), representing seven families: Echinostomatidae, Opecoelidae, Microphallidae, Strigeidae and three, as yet, undetermined families A, B and C. Each parasite family infected between one and three host whelk species, and infection levels were typically low (average infection rates ranged from 1·4 to 3·6%). Host specificity ranged from highly species-specific amongst the echinostomes, which were only ever observed infecting C. glandiformis, to the more generalist opecoelids and strigeids, which were capable of infecting three out of four of the Cominella...
Current taxonomic treatments of New Zealand and temperate Australian members of the gastropod sub... more Current taxonomic treatments of New Zealand and temperate Australian members of the gastropod subfamily Cantharidinae imply that species on either side of the Tasman Sea are closely related and, in some cases, congeneric. Such a close relationship, however, entails a relatively recent divergence of Australian and New Zealand lineages, which seems inconsistent with what is known about cantharidine larval development in general. In order to address these issues, mitochondrial and nuclear DNA sequences were used to ascertain how cantharidine genera became established over the wide geographical range of temperate Australia and New Zealand, including their subantarctic islands. Our robust and dated phylogenies (based on 16S, COI, 12S and 28S sequences) revealed that Australian and New Zealand species fall into endemic clades that have been separated for, at most, 35million years. This divergence date postdates a vicariant split by around 50million years and we suggest that, once again, long-distance trans-Tasman dispersal has played a pivotal role in molluscan evolution in this part of the world. Our results also show that the current classification requires revision. We recognize three genera (Cantharidus [comprising 2 subgenera: Cantharidus s.str. and Pseudomargarella n. subgen.], Micrelenchus [comprising 2 subgenera: Micrelenchus s.str. and Mawhero] and Roseaplagis n. gen.) for New Zealand cantharidine species. In our dated BEAST tree, these genera form a clade with the endemic Australian Prothalotia and South African Oxystele. Other temperate Australian cantharidines in our study fall into previously recognized genera (Phasianotrochus, Thalotia, Calthalotia), which are all quite distinct from Cantharidus in spite of some authors considering various of them to be possible synonyms. Finally, we remove the Australian genus Cantharidella from the Cantharidinae to the subfamily Trochinae and erect a new genus, Cratidentium n. gen., also in the Trochinae, to accommodate several Australian species previously considered to belong to Cantharidella.
In the marine cyanobacterium Synechococcus sp. strain WH7803, PstS is a 32-kDa cell wall-associat... more In the marine cyanobacterium Synechococcus sp. strain WH7803, PstS is a 32-kDa cell wall-associated phosphate-binding protein specifically synthesized under conditions of restricted inorganic phosphate (P1) availability (D. J. Scanlan, N. H. Mann, and N. G. Carr, Mol. Microbiol. 10:181-191, 1993). We have assessed its use as a potential diagnostic marker for the P status of photosynthetic picoplankton. Expression of PstS in Synechococcus sp. strain WH7803 was observed when the P1 concentration fell below 50 nM, demonstrating that the protein is induced at concentrations of P1 typical of oligotrophic conditions. PstS expression could be specifically detected by use of standard Western blotting (immunoblotting) techniques in natural mesocosm samples under conditions in which the N/P ratio was artificially manipulated to force P depletion. In addition, we have developed an immunofluorescence assay that can detect PstS expression in single Synechococcus cells both in laboratory cultures...
ABSTRACT The turritellid Maoricolpus roseus (Quoy & Gaimard, 1834) is abundant in low int... more ABSTRACT The turritellid Maoricolpus roseus (Quoy & Gaimard, 1834) is abundant in low intertidal and shallow water marine environments around the coasts of New Zealand. It is currently divided into two regional subspecies: M. roseus roseus, common around much of New Zealand’s coast; and M. roseus manukauensis, restricted to several west coast harbours in the North Island, specifically Manukau, Raglan and Kawhia. Molecular data, consisting of both mitochondrial (16S rRNA and cytochrome oxidase I (COI)) and nuclear (18S rRNA and 28S rRNA) genes, were collected and analysed to resolve the status of these subspecies. Our analyses reveal that neither subspecies is monophyletic in our phylogenetic trees, and that the genetic distances between them are no greater than those within. We thus argue that M. roseus manukauensis should be synonymised with the nominotypical subspecies. Maoricolpus roseus is a morphologically variable species, with low levels of 16S and COI genetic diversity within and among different populations.
The systematics of topshells (family Trochidae) is currently unresolved: at present even the gene... more The systematics of topshells (family Trochidae) is currently unresolved: at present even the generic boundaries within this group are poorly defined. In this study, we used sequence data of two mitochondrial genes (16S and cytochrome oxidase 1, COI) and one nuclear gene (actin) to resolve the phylogeny of a closely related subgroup of the Trochidae, 30 species of largely Southern Hemisphere monodontine topshells. The phylogenies constructed revealed five well-supported generic clades: a South African clade (genus Oxystele Philippi, 1847), which lay basally to four internal Pacific clades (genera Chlorodiloma Pilsbry, 1889; Monodonta Lamarck, 1799; Austrocochlea Fischer, 1885; and Diloma Philippi, 1845). The molecular phylogenies constructed in this study shed light on previously unresolved relationships between different groups of topshells, allowing for the first time assignation (based on DNA sequence) of clearly defined, well-supported taxonomic and nomenclatural classification of monodontine topshells species. Austrocochlea crinita (Philippi, 1849), A. odontis (Wood, 1828), A. adelaidae (Philippi, 1849), and A. millelineata (Bonnet, 1864) are placed in the genus Chlorodiloma, which we resurrect from synonymy with Austrocochlea. The Japanese M. confusa Tapparone-Canefri, 1874 is treated as a separate species from M. labio (Linné, 1758). Melagraphia Gray, 1847 is synonymised with Diloma and its sole member, M. aethiops (Gmelin, 1791), along with A. concamerata (Wood, 1828), is transferred to that genus. The Juan Fernandez endemic D. crusoeana (Pilsbry, 1889) is synonymised with D. nigerrima (Gmelin, 1791). We find that morphologically cryptic species are not necessarily close genetically.
Abstract Leucine aminopeptidase (LAP) belongs to a family of ubiquitous peptidases, with roles in... more Abstract Leucine aminopeptidase (LAP) belongs to a family of ubiquitous peptidases, with roles in growth and development, stress responses and adaptation to changing environmental conditions. The LAP gene was sequenced from a commercially important ...
In New Zealand, a single morphotype, comprising three genetically distinct opecoelid species, inf... more In New Zealand, a single morphotype, comprising three genetically distinct opecoelid species, infects four sympatric species of trochid snails. Two species (a and b) are specific to Diloma subrostrata while the third (c) is more general, capable of infecting three species, most commonly D. aethiops but never D. subrostrata. We sampled three D. subrostrata and D. aethiops populations, in which infection levels ranged from 0 to 29.2%, and attempted species assignation based on host information, restriction fragment length polymorphism (RFLP) analysis and morphology. Host information allowed reliable separation of species a and b from species c. Restriction mapping of ribosomal DNA internal transcriber spacer 2 (ITS2) demonstrated that the restriction enzyme SfuI only digested ITS2 from species b and c. Thus, restriction digests + host species information allowed reliable species assignation. Morphological measurements were taken for both sporocysts and cercariae dissected from 83 infected snails. Substantial overlap existed between measurements for the three species, and discriminant analysis showed that parasites could not be unequivocally assigned to a species--error rates ranged from 9 to 58%--despite statistically significant differences among several means. Amongst this group of digeneans, host information + RFLP provide a rapid, unambiguous method of species assignation that host information + morphological measurements cannot.
Journal of Experimental Marine Biology and Ecology, 2011
This study of population structure of two intertidal monodontine species: Diloma nigerrima and Di... more This study of population structure of two intertidal monodontine species: Diloma nigerrima and Diloma subrostrata, revealed the level of genetic connectedness among populations. Despite their markedly different geographic ranges (D. nigerrima is a geographically widespread species, inhabiting both Chile and New Zealand, including its subantarctic islands, whereas D. subrostrata is endemic to New Zealand), both species are believed to possess
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