Mitochondrial DNA paradox: sex-specific genetic structure in a marine mussel despite maternal inheritance and passive dispersal
- Teske, Peter R, Papadopoulos, Isabelle, Barker, Nigel P, McQuaid, Christopher D
- Authors: Teske, Peter R , Papadopoulos, Isabelle , Barker, Nigel P , McQuaid, Christopher D
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6836 , http://hdl.handle.net/10962/d1010959
- Description: Background: When genetic structure is identified using mitochondrial DNA (mtDNA), but no structure is identified using biparentally-inherited nuclear DNA, the discordance is often attributed to differences in dispersal potential between the sexes. Results: We sampled the intertidal rocky shore mussel Perna perna in a South African bay and along the nearby open coast, and sequenced maternally-inherited mtDNA (there is no evidence for paternally-inherited mtDNA in this species) and a biparentally-inherited marker. By treating males and females as different populations, we identified significant genetic structure on the basis of mtDNA data in the females only. Conclusions: This is the first study to report sex-specific differences in genetic structure based on matrilineally-inherited mtDNA in a passively dispersing species that lacks social structure or sexual dimorphism. The observed pattern most likely stems from females being more vulnerable to selection in habitats from which they did not originate, which also manifests itself in a male-biased sex ratio. Our results have three important implications for the interpretation of population genetic data. First, even when mtDNA is inherited exclusively in the female line, it also contains information about males. For that reason, using it to identify sex-specific differences in genetic structure by contrasting it with biparentally-inherited markers is problematic. Second, the fact that sex-specific differences were found in a passively dispersing species in which sex-biased dispersal is unlikely highlights the fact that significant genetic structure is not necessarily a function of low dispersal potential or physical barriers. Third, even though mtDNA is typically used to study historical demographic processes, it also contains information about contemporary processes. Higher survival rates of males in non-native habitats can erase the genetic structure present in their mothers within a single generation.
- Full Text:
- Authors: Teske, Peter R , Papadopoulos, Isabelle , Barker, Nigel P , McQuaid, Christopher D
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6836 , http://hdl.handle.net/10962/d1010959
- Description: Background: When genetic structure is identified using mitochondrial DNA (mtDNA), but no structure is identified using biparentally-inherited nuclear DNA, the discordance is often attributed to differences in dispersal potential between the sexes. Results: We sampled the intertidal rocky shore mussel Perna perna in a South African bay and along the nearby open coast, and sequenced maternally-inherited mtDNA (there is no evidence for paternally-inherited mtDNA in this species) and a biparentally-inherited marker. By treating males and females as different populations, we identified significant genetic structure on the basis of mtDNA data in the females only. Conclusions: This is the first study to report sex-specific differences in genetic structure based on matrilineally-inherited mtDNA in a passively dispersing species that lacks social structure or sexual dimorphism. The observed pattern most likely stems from females being more vulnerable to selection in habitats from which they did not originate, which also manifests itself in a male-biased sex ratio. Our results have three important implications for the interpretation of population genetic data. First, even when mtDNA is inherited exclusively in the female line, it also contains information about males. For that reason, using it to identify sex-specific differences in genetic structure by contrasting it with biparentally-inherited markers is problematic. Second, the fact that sex-specific differences were found in a passively dispersing species in which sex-biased dispersal is unlikely highlights the fact that significant genetic structure is not necessarily a function of low dispersal potential or physical barriers. Third, even though mtDNA is typically used to study historical demographic processes, it also contains information about contemporary processes. Higher survival rates of males in non-native habitats can erase the genetic structure present in their mothers within a single generation.
- Full Text:
Connectivity between marine reserves and exploited areas in the philopatric reef fish Chrysoblephus laticeps (Teleostei: Sparidae)
- Teske, Peter R, Forget, Fabian R G, Cowley, Paul D, von der Heyden, S, Beheregaray, Luciano B
- Authors: Teske, Peter R , Forget, Fabian R G , Cowley, Paul D , von der Heyden, S , Beheregaray, Luciano B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6776 , http://hdl.handle.net/10962/d1008086
- Description: "No-take‟ Marine Protected Areas (MPAs) are successful in protecting populations of many exploited fish species, but it is often unclear whether networks of MPAs are adequately spaced to ensure connectivity among reserves, and whether spillover occurs into adjacent exploited areas. Such issues are particularly important in species with low dispersal potential, many of which exist as genetically distinct regional stocks.The roman, Chrysoblephus laticeps, is an overexploited, commercially important fishery species endemic to South Africa. Post-recruits display resident behavior and occupy small home ranges, making C. laticeps a suitable model species to investigate connectivity in marine teleosts with potentially low dispersal ability. We used multilocus data from two types of highly variable genetic markers (mitochondrial DNA control region and microsatellites) to clarify patterns of genetic connectivity and population structure in C. laticeps using samples from two MPAs and several moderately or severely exploited regions. Despite using analytical tools that are sensitive to detect even subtle genetic structure, we found that this species exists as a single, well-mixed stock throughout its core distribution. This finding lends supports to the status of MPAs as an adequate tool for managing overexploited marine teleosts. Even though adult dispersal out of MPAs is limited, the fact that the large adults in these reserves produce exponentially more offspring than their smaller counterparts in exploited areas makes MPAs a rich source of recruits. We nonetheless caution against concluding that the lack of structure identified in C. laticeps and several other southern African teleosts can be considered to be representative of marine teleosts in this region in general. Many such species are represented in more than one marine biogeographic province and may be comprised of regionally-adapted stocks that need to be managed individually.
- Full Text:
- Authors: Teske, Peter R , Forget, Fabian R G , Cowley, Paul D , von der Heyden, S , Beheregaray, Luciano B
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6776 , http://hdl.handle.net/10962/d1008086
- Description: "No-take‟ Marine Protected Areas (MPAs) are successful in protecting populations of many exploited fish species, but it is often unclear whether networks of MPAs are adequately spaced to ensure connectivity among reserves, and whether spillover occurs into adjacent exploited areas. Such issues are particularly important in species with low dispersal potential, many of which exist as genetically distinct regional stocks.The roman, Chrysoblephus laticeps, is an overexploited, commercially important fishery species endemic to South Africa. Post-recruits display resident behavior and occupy small home ranges, making C. laticeps a suitable model species to investigate connectivity in marine teleosts with potentially low dispersal ability. We used multilocus data from two types of highly variable genetic markers (mitochondrial DNA control region and microsatellites) to clarify patterns of genetic connectivity and population structure in C. laticeps using samples from two MPAs and several moderately or severely exploited regions. Despite using analytical tools that are sensitive to detect even subtle genetic structure, we found that this species exists as a single, well-mixed stock throughout its core distribution. This finding lends supports to the status of MPAs as an adequate tool for managing overexploited marine teleosts. Even though adult dispersal out of MPAs is limited, the fact that the large adults in these reserves produce exponentially more offspring than their smaller counterparts in exploited areas makes MPAs a rich source of recruits. We nonetheless caution against concluding that the lack of structure identified in C. laticeps and several other southern African teleosts can be considered to be representative of marine teleosts in this region in general. Many such species are represented in more than one marine biogeographic province and may be comprised of regionally-adapted stocks that need to be managed individually.
- Full Text:
Tri-locus sequence data reject a Gondwanan origin hypothesis for the African/South Pacific crab genus Hymenosoma
- Teske, Peter R, McLay, Colin L, Sandoval-Castillo, Jonathan, Papadopoulos, Isabelle, Newman, Brent K, Griffiths, Charles L, McQuaid, Christopher D, Barker, Nigel P, Borgonie, Gaetan, Beheregaray, Luciano B
- Authors: Teske, Peter R , McLay, Colin L , Sandoval-Castillo, Jonathan , Papadopoulos, Isabelle , Newman, Brent K , Griffiths, Charles L , McQuaid, Christopher D , Barker, Nigel P , Borgonie, Gaetan , Beheregaray, Luciano B
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6547 , http://hdl.handle.net/10962/d1006003
- Description: Crabs of the family Hymenosomatidae are common in coastal and shelf regions throughout much of the southern hemisphere. One of the genera in the family, Hymenosoma, is represented in Africa and the South Pacific (Australia and New Zealand). This distribution can be explained either by vicariance (presence of the genus on the Gondwanan supercontinent and divergence following its break-up) or more recent transoceanic dispersal from one region to the other. We tested these hypotheses by reconstructing phylogenetic relationships among the seven presently-accepted species in the genus, as well as examining their placement among other hymenosomatid crabs, using sequence data from two nuclear markers (Adenine Nucleotide Transporter [ANT] exon 2 and 18S rDNA) and three mitochondrial markers (COI, 12S and 16S rDNA). The five southern African representatives of the genus were recovered as a monophyletic lineage, and another southern African species, Neorhynchoplax bovis, was identified as their sister taxon. The two species of Hymenosoma from the South Pacific neither clustered with their African congeners, nor with each other, and should therefore both be placed into different genera. Molecular dating supports a post-Gondwanan origin of the Hymenosomatidae. While long-distance dispersal cannot be ruled out to explain the presence of the family Hymenosomatidae on the former Gondwanan land-masses and beyond, the evolutionary history of the African species of Hymenosoma indicates that a third means of speciation may be important in this group: gradual along-coast dispersal from tropical towards temperate regions, with range expansions into formerly inhospitable habitat during warm climatic phases, followed by adaptation and speciation during subsequent cooler phases.
- Full Text:
- Authors: Teske, Peter R , McLay, Colin L , Sandoval-Castillo, Jonathan , Papadopoulos, Isabelle , Newman, Brent K , Griffiths, Charles L , McQuaid, Christopher D , Barker, Nigel P , Borgonie, Gaetan , Beheregaray, Luciano B
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6547 , http://hdl.handle.net/10962/d1006003
- Description: Crabs of the family Hymenosomatidae are common in coastal and shelf regions throughout much of the southern hemisphere. One of the genera in the family, Hymenosoma, is represented in Africa and the South Pacific (Australia and New Zealand). This distribution can be explained either by vicariance (presence of the genus on the Gondwanan supercontinent and divergence following its break-up) or more recent transoceanic dispersal from one region to the other. We tested these hypotheses by reconstructing phylogenetic relationships among the seven presently-accepted species in the genus, as well as examining their placement among other hymenosomatid crabs, using sequence data from two nuclear markers (Adenine Nucleotide Transporter [ANT] exon 2 and 18S rDNA) and three mitochondrial markers (COI, 12S and 16S rDNA). The five southern African representatives of the genus were recovered as a monophyletic lineage, and another southern African species, Neorhynchoplax bovis, was identified as their sister taxon. The two species of Hymenosoma from the South Pacific neither clustered with their African congeners, nor with each other, and should therefore both be placed into different genera. Molecular dating supports a post-Gondwanan origin of the Hymenosomatidae. While long-distance dispersal cannot be ruled out to explain the presence of the family Hymenosomatidae on the former Gondwanan land-masses and beyond, the evolutionary history of the African species of Hymenosoma indicates that a third means of speciation may be important in this group: gradual along-coast dispersal from tropical towards temperate regions, with range expansions into formerly inhospitable habitat during warm climatic phases, followed by adaptation and speciation during subsequent cooler phases.
- Full Text:
Oceanic dispersal barriers, adaptation and larval retention: an interdisciplinary assessment of potential factors maintaining a phylogeographic break between sister lineages of an African prawn
- Teske, Peter R, Papadopoulos, Isabelle, Newman, Brent K, Dworschak, Peter C, McQuaid, Christopher D, Barker, Nigel P
- Authors: Teske, Peter R , Papadopoulos, Isabelle , Newman, Brent K , Dworschak, Peter C , McQuaid, Christopher D , Barker, Nigel P
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6546 , http://hdl.handle.net/10962/d1006002 , http://dx.doi.org/10.1186/1471-2148-8-341
- Description: Background. Genetic breaks separating regional lineages of marine organisms with potentially high broadcasting abilities are generally attributed either to dispersal barriers such as currents or upwelling, or to behavioural strategies promoting self-recruitment. We investigated whether such patterns could potentially also be explained by adaptations to different environmental conditions by studying two morphologically distinguishable genetic lineages of the estuarine mudprawn Upogebia africana across a biogeographic disjunction in south-eastern Africa. The study area encompasses a transition between temperate and subtropical biotas, where the warm, southward-flowing Agulhas Current is deflected away from the coast, and its inshore edge is characterised by intermittent upwelling. To determine how this phylogeographic break is maintained, we estimated gene flow among populations in the region, tested for isolation by distance as an indication of larval retention, and reared larvae of the temperate and subtropical lineages at a range of different temperatures. Results. Of four populations sampled, the two northernmost exclusively included the subtropical lineage, a central population had a mixture of both lineages, and the southernmost estuary had only haplotypes of the temperate lineage. No evidence was found for isolation by distance, and gene flow was bidirectional and of similar magnitude among adjacent populations. In both lineages, the optimum temperature for larval development was at about 23°C, but a clear difference was found at lower temperatures. While larvae of the temperate lineage could complete development at temperatures as low as 12°C, those of the subtropical lineage did not complete development below 17°C. Conclusion. The results indicate that both southward dispersal of the subtropical lineage inshore of the Agulhas Current, and its establishment in the temperate province, may be limited primarily by low water temperatures. There is no evidence that the larvae of the temperate lineage would survive less well in the subtropical province than in their native habitat, and their exclusion from this region may be due to a combination of upwelling, short larval duration with limited dispersal potential near the coast, plus transport away from the coast of larvae that become entrained in the Agulhas Current. This study shows how methods from different fields of research (genetics, physiology, oceanography and morphology) can be combined to study phylogeographic patterns.
- Full Text:
- Authors: Teske, Peter R , Papadopoulos, Isabelle , Newman, Brent K , Dworschak, Peter C , McQuaid, Christopher D , Barker, Nigel P
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6546 , http://hdl.handle.net/10962/d1006002 , http://dx.doi.org/10.1186/1471-2148-8-341
- Description: Background. Genetic breaks separating regional lineages of marine organisms with potentially high broadcasting abilities are generally attributed either to dispersal barriers such as currents or upwelling, or to behavioural strategies promoting self-recruitment. We investigated whether such patterns could potentially also be explained by adaptations to different environmental conditions by studying two morphologically distinguishable genetic lineages of the estuarine mudprawn Upogebia africana across a biogeographic disjunction in south-eastern Africa. The study area encompasses a transition between temperate and subtropical biotas, where the warm, southward-flowing Agulhas Current is deflected away from the coast, and its inshore edge is characterised by intermittent upwelling. To determine how this phylogeographic break is maintained, we estimated gene flow among populations in the region, tested for isolation by distance as an indication of larval retention, and reared larvae of the temperate and subtropical lineages at a range of different temperatures. Results. Of four populations sampled, the two northernmost exclusively included the subtropical lineage, a central population had a mixture of both lineages, and the southernmost estuary had only haplotypes of the temperate lineage. No evidence was found for isolation by distance, and gene flow was bidirectional and of similar magnitude among adjacent populations. In both lineages, the optimum temperature for larval development was at about 23°C, but a clear difference was found at lower temperatures. While larvae of the temperate lineage could complete development at temperatures as low as 12°C, those of the subtropical lineage did not complete development below 17°C. Conclusion. The results indicate that both southward dispersal of the subtropical lineage inshore of the Agulhas Current, and its establishment in the temperate province, may be limited primarily by low water temperatures. There is no evidence that the larvae of the temperate lineage would survive less well in the subtropical province than in their native habitat, and their exclusion from this region may be due to a combination of upwelling, short larval duration with limited dispersal potential near the coast, plus transport away from the coast of larvae that become entrained in the Agulhas Current. This study shows how methods from different fields of research (genetics, physiology, oceanography and morphology) can be combined to study phylogeographic patterns.
- Full Text:
Climate change, genetics or human choice: why were the shells of mankind’s earliest ornament larger in the Pleistocene than in the Holocene?
- Teske, Peter R, Papadopoulos, Isabelle, McQuaid, Christopher D, Newman, Brent K, Barker, Nigel P
- Authors: Teske, Peter R , Papadopoulos, Isabelle , McQuaid, Christopher D , Newman, Brent K , Barker, Nigel P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6952 , http://hdl.handle.net/10962/d1011984
- Description: The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest known ornamental object used by human beings. Shell beads dated from ~75,000 years ago (Pleistocene era) were found in a cave located on South Africa's south coast. Beads made from N. kraussianus shells have also been found in deposits in this region dating from the beginning of the Holocene era (<10,000 years ago). These younger shells were significantly smaller, a phenomenon that has been attributed to a change in human preference. We investigated two alternative hypotheses explaining the difference in shell size: a) N. kraussianus comprises at least two genetic lineages that differ in size; b) the difference in shell size is due to phenotypic plasticity and is a function of environmental conditions. To test these hypotheses, we first reconstructed the species' phylogeographic history, and second, we measured the shell sizes of extant individuals throughout South Africa. Although two genetic lineages were identified, the sharing of haplotypes between these suggests that there is no genetic basis for the size differences. Extant individuals from the cool temperate west coast had significantly larger shells than populations in the remainder of the country, suggesting that N. kraussianus grows to a larger size in colder water. The decrease in fossil shell size from Pleistocene to Holocene was likely due to increased temperatures as a result of climate change at the beginning of the present interglacial period. We hypothesise that the sizes of N. kraussianus fossil shells can therefore serve as indicators of the climatic conditions that were prevalent in a particular region at the time when they were deposited. Moreover, N. kraussianus could serve as a biomonitor to study the impacts of future climate change on coastal biota in southern Africa.
- Full Text:
- Authors: Teske, Peter R , Papadopoulos, Isabelle , McQuaid, Christopher D , Newman, Brent K , Barker, Nigel P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6952 , http://hdl.handle.net/10962/d1011984
- Description: The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest known ornamental object used by human beings. Shell beads dated from ~75,000 years ago (Pleistocene era) were found in a cave located on South Africa's south coast. Beads made from N. kraussianus shells have also been found in deposits in this region dating from the beginning of the Holocene era (<10,000 years ago). These younger shells were significantly smaller, a phenomenon that has been attributed to a change in human preference. We investigated two alternative hypotheses explaining the difference in shell size: a) N. kraussianus comprises at least two genetic lineages that differ in size; b) the difference in shell size is due to phenotypic plasticity and is a function of environmental conditions. To test these hypotheses, we first reconstructed the species' phylogeographic history, and second, we measured the shell sizes of extant individuals throughout South Africa. Although two genetic lineages were identified, the sharing of haplotypes between these suggests that there is no genetic basis for the size differences. Extant individuals from the cool temperate west coast had significantly larger shells than populations in the remainder of the country, suggesting that N. kraussianus grows to a larger size in colder water. The decrease in fossil shell size from Pleistocene to Holocene was likely due to increased temperatures as a result of climate change at the beginning of the present interglacial period. We hypothesise that the sizes of N. kraussianus fossil shells can therefore serve as indicators of the climatic conditions that were prevalent in a particular region at the time when they were deposited. Moreover, N. kraussianus could serve as a biomonitor to study the impacts of future climate change on coastal biota in southern Africa.
- Full Text:
Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
- Teske, Peter R, Lockyear, Jaqueline F, Hecht, Thomas, Kaiser, Horst
- Authors: Teske, Peter R , Lockyear, Jaqueline F , Hecht, Thomas , Kaiser, Horst
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6775 , http://hdl.handle.net/10962/d1008082
- Description: The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area.
- Full Text:
- Authors: Teske, Peter R , Lockyear, Jaqueline F , Hecht, Thomas , Kaiser, Horst
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6775 , http://hdl.handle.net/10962/d1008082
- Description: The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area.
- Full Text:
Phylogeographic structure of Octopus vulgaris in South Africa revisited: identification of a second lineage near Durban harbor
- Teske, Peter R, Oosthuizen, A, Papadopoulos, Isabelle, Barker, Nigel P
- Authors: Teske, Peter R , Oosthuizen, A , Papadopoulos, Isabelle , Barker, Nigel P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6544 , http://hdl.handle.net/10962/d1006000
- Description: In a previous study that investigated genetic structure of Octopus vulgaris along the South African coast by sequencing the mitochondrial cytochrome oxidase III gene (COIII), all sequences generated were identical. Such a finding is unusual, because mitochondrial DNA mutates quickly, and several marine invertebrates present in southern Africa show considerable genetic variation and structure. We reanalysed the samples using two different mitochondrial markers, namely cytochrome oxidase I (COI) and the large ribosomal subunit (16S rRNA). Sequences of both these markers showed variation. The conclusion of the previous study, that South Africa’s O. vulgaris population is characterised by a lack of genetic structure along the coast, is rejected. Some specimens from Durban (southeast Africa) were genetically more different from those found in the remainder of the country than were specimens from other regions (Tristan da Cunha and Senegal). We suggest that the lineage in Durban may have been recently introduced.
- Full Text:
- Authors: Teske, Peter R , Oosthuizen, A , Papadopoulos, Isabelle , Barker, Nigel P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6544 , http://hdl.handle.net/10962/d1006000
- Description: In a previous study that investigated genetic structure of Octopus vulgaris along the South African coast by sequencing the mitochondrial cytochrome oxidase III gene (COIII), all sequences generated were identical. Such a finding is unusual, because mitochondrial DNA mutates quickly, and several marine invertebrates present in southern Africa show considerable genetic variation and structure. We reanalysed the samples using two different mitochondrial markers, namely cytochrome oxidase I (COI) and the large ribosomal subunit (16S rRNA). Sequences of both these markers showed variation. The conclusion of the previous study, that South Africa’s O. vulgaris population is characterised by a lack of genetic structure along the coast, is rejected. Some specimens from Durban (southeast Africa) were genetically more different from those found in the remainder of the country than were specimens from other regions (Tristan da Cunha and Senegal). We suggest that the lineage in Durban may have been recently introduced.
- Full Text:
Signatures of seaway closures and founder dispersal in the phylogeny of a circumglobally distributed seahorse lineage
- Teske, Peter R, Hamilton, Healy, Matthee, Conrad A, Barker, Nigel P
- Authors: Teske, Peter R , Hamilton, Healy , Matthee, Conrad A , Barker, Nigel P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6549 , http://hdl.handle.net/10962/d1006005
- Description: The importance of vicariance events on the establishment of phylogeographic patterns in the marine environment is well documented, and generally accepted as an important cause of cladogenesis. Founder dispersal (i.e. long-distance dispersal followed by founder effect speciation) is also frequently invoked as a cause of genetic divergence among lineages, but its role has long been challenged by vicariance biogeographers. Founder dispersal is likely to be common in species that colonize remote habitats by means of rafting (e.g. seahorses), as long-distance dispersal events are likely to be rare and subsequent additional recruitment from the source habitat is unlikely. In the present study, the relative importance of vicariance and founder dispersal as causes of cladogenesis in a circumglobally distributed seahorse lineage was investigated using molecular dating. A phylogeny was reconstructed using sequence data from mitochondrial and nuclear markers, and the well-documented closure of the Central American seaway was used as a primary calibration point to test whether other bifurcations in the phylogeny could also have been the result of vicariance events. The feasibility of three other vicariance events was explored: a) the closure of the Indonesian Seaway, resulting in sister lineages associated with the Indian Ocean and West Pacific, respectively; b) the closure of the Tethyan Seaway, resulting in sister lineages associated with the Indo-Pacific and Atlantic Ocean, respectively, and c) continental break-up during the Mesozoic followed by spreading of the Atlantic Ocean, resulting in pairs of lineages with amphi-Atlantic distribution patterns.
- Full Text:
- Authors: Teske, Peter R , Hamilton, Healy , Matthee, Conrad A , Barker, Nigel P
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6549 , http://hdl.handle.net/10962/d1006005
- Description: The importance of vicariance events on the establishment of phylogeographic patterns in the marine environment is well documented, and generally accepted as an important cause of cladogenesis. Founder dispersal (i.e. long-distance dispersal followed by founder effect speciation) is also frequently invoked as a cause of genetic divergence among lineages, but its role has long been challenged by vicariance biogeographers. Founder dispersal is likely to be common in species that colonize remote habitats by means of rafting (e.g. seahorses), as long-distance dispersal events are likely to be rare and subsequent additional recruitment from the source habitat is unlikely. In the present study, the relative importance of vicariance and founder dispersal as causes of cladogenesis in a circumglobally distributed seahorse lineage was investigated using molecular dating. A phylogeny was reconstructed using sequence data from mitochondrial and nuclear markers, and the well-documented closure of the Central American seaway was used as a primary calibration point to test whether other bifurcations in the phylogeny could also have been the result of vicariance events. The feasibility of three other vicariance events was explored: a) the closure of the Indonesian Seaway, resulting in sister lineages associated with the Indian Ocean and West Pacific, respectively; b) the closure of the Tethyan Seaway, resulting in sister lineages associated with the Indo-Pacific and Atlantic Ocean, respectively, and c) continental break-up during the Mesozoic followed by spreading of the Atlantic Ocean, resulting in pairs of lineages with amphi-Atlantic distribution patterns.
- Full Text:
Impacts of marine biogeographic boundaries on phylogeographic patterns of three South African estuarine crustaceans
- Teske, Peter R, McQuaid, Christopher D, Froneman, P William, Barker, Nigel P
- Authors: Teske, Peter R , McQuaid, Christopher D , Froneman, P William , Barker, Nigel P
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6548 , http://hdl.handle.net/10962/d1006004 , http://dx.doi.org/10.3354/meps314283
- Description: The South African coastline comprises 3 main biogeographic provinces: (1) the cool-temperate west coast, (2) the warm-temperate south coast, and (3) the subtropical east coast. The boundaries between these regions are defined by changes in species compositions and hydrological conditions. It is possible that these affect phylogeographic patterns of coastal organisms differently, depending on the species’ ecologies and modes of dispersal. In the present study, genealogies of 3 estuarine crustaceans, each characterized by a different mode of passive dispersal and present in more than one biogeographic province, were reconstructed using mtDNA COI sequences, and the impacts of biogeographic boundaries on their phylogeographic patterns were compared. The species were (mode of dispersal in brackets): (1) the mudprawn Upogebia africana (planktonic larvae), (2) the isopod Exosphaeroma hylecoetes (adult rafting), and (3) the cumacean Iphinoe truncata (adult drifting). Two major mtDNA lineages with slightly overlapping distributions were identified in U. africana (the species with the highest dispersal potential). The other 2 species had 3 mtDNA lineages each, which were characterized by strict geographic segregation. Phylogeographic breaks in U. africana and E. hylecoetes coincided with biogeographic boundaries, whereas the phylogeographic patterns identified in I. truncata may reflect persistent palaeogeographic patterns. Ecological factors and modes of dispersal are likely to have played a role in both cladogenesis of the different lineages and in the establishment of their present-day distribution patterns.
- Full Text:
- Authors: Teske, Peter R , McQuaid, Christopher D , Froneman, P William , Barker, Nigel P
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6548 , http://hdl.handle.net/10962/d1006004 , http://dx.doi.org/10.3354/meps314283
- Description: The South African coastline comprises 3 main biogeographic provinces: (1) the cool-temperate west coast, (2) the warm-temperate south coast, and (3) the subtropical east coast. The boundaries between these regions are defined by changes in species compositions and hydrological conditions. It is possible that these affect phylogeographic patterns of coastal organisms differently, depending on the species’ ecologies and modes of dispersal. In the present study, genealogies of 3 estuarine crustaceans, each characterized by a different mode of passive dispersal and present in more than one biogeographic province, were reconstructed using mtDNA COI sequences, and the impacts of biogeographic boundaries on their phylogeographic patterns were compared. The species were (mode of dispersal in brackets): (1) the mudprawn Upogebia africana (planktonic larvae), (2) the isopod Exosphaeroma hylecoetes (adult rafting), and (3) the cumacean Iphinoe truncata (adult drifting). Two major mtDNA lineages with slightly overlapping distributions were identified in U. africana (the species with the highest dispersal potential). The other 2 species had 3 mtDNA lineages each, which were characterized by strict geographic segregation. Phylogeographic breaks in U. africana and E. hylecoetes coincided with biogeographic boundaries, whereas the phylogeographic patterns identified in I. truncata may reflect persistent palaeogeographic patterns. Ecological factors and modes of dispersal are likely to have played a role in both cladogenesis of the different lineages and in the establishment of their present-day distribution patterns.
- Full Text:
- «
- ‹
- 1
- ›
- »