Intraspecific mitochondrial gene variation can be as low as that of nuclear rRNA:
- Matumba, Tshifhiwa G, Oliver, Jody, Barker, Nigel P, McQuaid, Christopher D, Teske, Peter R
- Authors: Matumba, Tshifhiwa G , Oliver, Jody , Barker, Nigel P , McQuaid, Christopher D , Teske, Peter R
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160401 , vital:40442 , https://doi.org/10.12688/f1000research.23635.2
- Description: Mitochondrial DNA (mtDNA) has long been used to date historical demographic events. The idea that it is useful for molecular dating rests on the premise that its evolution is neutral. Even though this idea has long been challenged, the evidence against clock-like evolution of mtDNA is often ignored. Here, we present a particularly clear and simple example to illustrate the implications of violations of the assumption of selective neutrality.
- Full Text:
- Authors: Matumba, Tshifhiwa G , Oliver, Jody , Barker, Nigel P , McQuaid, Christopher D , Teske, Peter R
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160401 , vital:40442 , https://doi.org/10.12688/f1000research.23635.2
- Description: Mitochondrial DNA (mtDNA) has long been used to date historical demographic events. The idea that it is useful for molecular dating rests on the premise that its evolution is neutral. Even though this idea has long been challenged, the evidence against clock-like evolution of mtDNA is often ignored. Here, we present a particularly clear and simple example to illustrate the implications of violations of the assumption of selective neutrality.
- Full Text:
Microplastic leachates induce species-specific trait strengthening in intertidal mussels:
- Seuront, Laurent, Nicastro, Katy, McQuaid, Christopher D, Zardi, Gerardo I
- Authors: Seuront, Laurent , Nicastro, Katy , McQuaid, Christopher D , Zardi, Gerardo I
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158200 , vital:40162 , https://0-doi.org.wam.seals.ac.za/10.1002/eap.2222. https://doi.org/10.5061/dryad.905qftthq
- Description: Plastic pollution is ubiquitous with increasing recognition of its direct effects on species’ fitness. Little is known, however, about its more subtle effects, including the influence of plastic pollution on the morphological, functional and behavioural traits of organisms that are central to their ability to withstand disturbances. Among the least obvious but most pernicious forms of plastic-associated pollution are the chemicals that leach from microplastics. Here, we investigate how such leachates influence species’ traits by assessing functional trait compensation across four species of intertidal mussels, through investigations of byssal thread production, movement and aggregation behaviour for mussels held in natural seawater or seawater contaminated by microplastic leachates.
- Full Text:
- Authors: Seuront, Laurent , Nicastro, Katy , McQuaid, Christopher D , Zardi, Gerardo I
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158200 , vital:40162 , https://0-doi.org.wam.seals.ac.za/10.1002/eap.2222. https://doi.org/10.5061/dryad.905qftthq
- Description: Plastic pollution is ubiquitous with increasing recognition of its direct effects on species’ fitness. Little is known, however, about its more subtle effects, including the influence of plastic pollution on the morphological, functional and behavioural traits of organisms that are central to their ability to withstand disturbances. Among the least obvious but most pernicious forms of plastic-associated pollution are the chemicals that leach from microplastics. Here, we investigate how such leachates influence species’ traits by assessing functional trait compensation across four species of intertidal mussels, through investigations of byssal thread production, movement and aggregation behaviour for mussels held in natural seawater or seawater contaminated by microplastic leachates.
- Full Text:
Small scale habitat effects on anthropogenic litter material and sources in a coastal lagoon system:
- Velez, Nadja, Nicastro, Katy R, McQuaid, Christopher D, Zardi, Gerardi I
- Authors: Velez, Nadja , Nicastro, Katy R , McQuaid, Christopher D , Zardi, Gerardi I
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160489 , vital:40450 , https://doi.org/10.1016/j.marpolbul.2020.111689
- Description: Anthropogenic litter is ubiquitous throughout marine ecosystems, but its abundance and distribution are driven by complex interactions of distinct environmental factors and thus can be extremely heterogeneous. Here we compare the extent of anthropogenic litter pollution at a sheltered lagoon habitat and nearby open coast sites. Monthly surveys over a period of five months showed that both the types and sources of litter always differed significantly between lagoon and open coast sites.
- Full Text:
Small scale habitat effects on anthropogenic litter material and sources in a coastal lagoon system:
- Authors: Velez, Nadja , Nicastro, Katy R , McQuaid, Christopher D , Zardi, Gerardi I
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160489 , vital:40450 , https://doi.org/10.1016/j.marpolbul.2020.111689
- Description: Anthropogenic litter is ubiquitous throughout marine ecosystems, but its abundance and distribution are driven by complex interactions of distinct environmental factors and thus can be extremely heterogeneous. Here we compare the extent of anthropogenic litter pollution at a sheltered lagoon habitat and nearby open coast sites. Monthly surveys over a period of five months showed that both the types and sources of litter always differed significantly between lagoon and open coast sites.
- Full Text:
Evidence for rangewide panmixia despite multiple barriers to dispersal in a marine mussel
- Lourenço, Carla R, Nicastro, Katy R, McQuaid, Christopher D, Chefaoui, Rosa M, Assis, Jorge, Taleb, Mohammed Z, Zardi, Gerardo I
- Authors: Lourenço, Carla R , Nicastro, Katy R , McQuaid, Christopher D , Chefaoui, Rosa M , Assis, Jorge , Taleb, Mohammed Z , Zardi, Gerardo I
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59952 , vital:27714 , doi:10.1038/s41598-017-10753-9
- Description: Oceanographic features shape the distributional and genetic patterns of marine species by interrupting or promoting connections among populations. Although general patterns commonly arise, distributional ranges and genetic structure are species-specific and do not always comply with the expected trends. By applying a multimarker genetic approach combined with Lagrangian particle simulations (LPS) we tested the hypothesis that oceanographic features along northeastern Atlantic and Mediterranean shores influence dispersal potential and genetic structure of the intertidal mussel Perna perna. Additionally, by performing environmental niche modelling we assessed the potential and realized niche of P. perna along its entire native distributional range and the environmental factors that best explain its realized distribution. Perna perna showed evidence of panmixia across 4,000 km despite several oceanographic breaking points detected by LPS. This is probably the result of a combination of life history traits, continuous habitat availability and stepping-stone dynamics. Moreover, the niche modelling framework depicted minimum sea surface temperatures (SST) as the major factor shaping P. perna distributional range limits along its native areas. Forthcoming warming SST is expected to further change these limits and allow the species to expand its range polewards though this may be accompanied by retreat from warmer areas.
- Full Text:
- Authors: Lourenço, Carla R , Nicastro, Katy R , McQuaid, Christopher D , Chefaoui, Rosa M , Assis, Jorge , Taleb, Mohammed Z , Zardi, Gerardo I
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59952 , vital:27714 , doi:10.1038/s41598-017-10753-9
- Description: Oceanographic features shape the distributional and genetic patterns of marine species by interrupting or promoting connections among populations. Although general patterns commonly arise, distributional ranges and genetic structure are species-specific and do not always comply with the expected trends. By applying a multimarker genetic approach combined with Lagrangian particle simulations (LPS) we tested the hypothesis that oceanographic features along northeastern Atlantic and Mediterranean shores influence dispersal potential and genetic structure of the intertidal mussel Perna perna. Additionally, by performing environmental niche modelling we assessed the potential and realized niche of P. perna along its entire native distributional range and the environmental factors that best explain its realized distribution. Perna perna showed evidence of panmixia across 4,000 km despite several oceanographic breaking points detected by LPS. This is probably the result of a combination of life history traits, continuous habitat availability and stepping-stone dynamics. Moreover, the niche modelling framework depicted minimum sea surface temperatures (SST) as the major factor shaping P. perna distributional range limits along its native areas. Forthcoming warming SST is expected to further change these limits and allow the species to expand its range polewards though this may be accompanied by retreat from warmer areas.
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Morphologically similar, coexisting hard corals (Porites lobata and P. solida) display similar trophic isotopic ratios across reefs and depths
- Plass-Johnson, Jeremiah G, McQuaid, Christopher D, Hill, Jaclyn M
- Authors: Plass-Johnson, Jeremiah G , McQuaid, Christopher D , Hill, Jaclyn M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444598 , vital:74253 , https://doi.org/10.1071/MF14248
- Description: Recent studies using stable isotope analysis in scleractinian corals have highlighted strong inter- and intra-specific variability in isotopic ratios, but few have excluded the effects of morphology, which affects resource acquisition, potentially confounding this with metabolic differences among species. Differences in the stable isotopic (δ13C and δ15N) ratios of the coral host tissue and photosymbionts of two co-existing, morphologically similar Porites corals (P. lobata and P. solida) were examined across nested spatial scales (inter-reefs and intra-reef) and across depths in Zanzibar, Tanzania. There were few differences between species in either coral host or photosymbiont isotopic ratios, but the two tissues showed different spatial patterns. Photosymbionts showed variation only in their δ13C ratios, which differed among reefs, but not by depth. In contrast, the coral hosts differed in δ13C and δ15N values among reefs and also by depth. Within-reef differences among sites occurred only for photosymbionts at one reef. The absence of differences in isotopic ratios between the two Porites species across reefs and depths, confirms that highly related and morphologically similar scleractinian corals may occupy similar ecosystem niches, metabolising resources in a similar fashion. This suggests that resource partitioning among corals, and subsequent isotopic variability, is most likely driven by resource acquisition, rather than being inherently species-specific.
- Full Text:
- Authors: Plass-Johnson, Jeremiah G , McQuaid, Christopher D , Hill, Jaclyn M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444598 , vital:74253 , https://doi.org/10.1071/MF14248
- Description: Recent studies using stable isotope analysis in scleractinian corals have highlighted strong inter- and intra-specific variability in isotopic ratios, but few have excluded the effects of morphology, which affects resource acquisition, potentially confounding this with metabolic differences among species. Differences in the stable isotopic (δ13C and δ15N) ratios of the coral host tissue and photosymbionts of two co-existing, morphologically similar Porites corals (P. lobata and P. solida) were examined across nested spatial scales (inter-reefs and intra-reef) and across depths in Zanzibar, Tanzania. There were few differences between species in either coral host or photosymbiont isotopic ratios, but the two tissues showed different spatial patterns. Photosymbionts showed variation only in their δ13C ratios, which differed among reefs, but not by depth. In contrast, the coral hosts differed in δ13C and δ15N values among reefs and also by depth. Within-reef differences among sites occurred only for photosymbionts at one reef. The absence of differences in isotopic ratios between the two Porites species across reefs and depths, confirms that highly related and morphologically similar scleractinian corals may occupy similar ecosystem niches, metabolising resources in a similar fashion. This suggests that resource partitioning among corals, and subsequent isotopic variability, is most likely driven by resource acquisition, rather than being inherently species-specific.
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The effects of tissue type and body size on δ13C and δ15N values in parrotfish (Labridae) from Zanzibar, Tanzania
- Plass-Johnson, Jeremiah G, McQuaid, Christopher D, Hill, Jaclyn M
- Authors: Plass-Johnson, Jeremiah G , McQuaid, Christopher D , Hill, Jaclyn M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444638 , vital:74256 , https://doi.org/10.1111/jai.12746
- Description: Differences between the stable isotopic ratios (δ13C and δ15N) of two tissues (blood and muscle) from four species of East African coral reef parrotfishes (family: Labridae, tribe: Scarini) were analysed across a broad spectrum of body sizes. Comparison of isotopic ratios between the tissues allowed the assessment of using blood as an alternative tissue to muscle. In 2010–2011, constant differences between tissues (δblood minus δmuscle) were found across a broad range of sampled fish lengths. Linear relationships between the tissues, specific for an isotope, indicate that constants could be generated for converting blood isotope into muscle isotope values. Only one species, Chlorurus sordidus, displayed an inconsistent difference between tissues in δ15N, indicating that this ratio was dependent on fish length. The δ13C of both tissues was positively related linearly to fish length for three species, while δ15N showed no relationship with body length. The results are interpreted as indicating dietary consistency over days to weeks, the time of tissue turnover for blood and muscle, respectively. Lastly, differences among the species, even closely related species, show that the generation of tissue conversion constants is species‐specific.
- Full Text:
- Authors: Plass-Johnson, Jeremiah G , McQuaid, Christopher D , Hill, Jaclyn M
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444638 , vital:74256 , https://doi.org/10.1111/jai.12746
- Description: Differences between the stable isotopic ratios (δ13C and δ15N) of two tissues (blood and muscle) from four species of East African coral reef parrotfishes (family: Labridae, tribe: Scarini) were analysed across a broad spectrum of body sizes. Comparison of isotopic ratios between the tissues allowed the assessment of using blood as an alternative tissue to muscle. In 2010–2011, constant differences between tissues (δblood minus δmuscle) were found across a broad range of sampled fish lengths. Linear relationships between the tissues, specific for an isotope, indicate that constants could be generated for converting blood isotope into muscle isotope values. Only one species, Chlorurus sordidus, displayed an inconsistent difference between tissues in δ15N, indicating that this ratio was dependent on fish length. The δ13C of both tissues was positively related linearly to fish length for three species, while δ15N showed no relationship with body length. The results are interpreted as indicating dietary consistency over days to weeks, the time of tissue turnover for blood and muscle, respectively. Lastly, differences among the species, even closely related species, show that the generation of tissue conversion constants is species‐specific.
- Full Text:
Biogeographical boundaries, functional group structure and diversity of rocky shore communities along the Argentinean coast
- Wieters, Evie A, McQuaid, Christopher D, Palomo, Gabriela, Pappalardo, Paula
- Authors: Wieters, Evie A , McQuaid, Christopher D , Palomo, Gabriela , Pappalardo, Paula
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6835 , http://hdl.handle.net/10962/d1010956
- Description: We investigate the extent to which functional structure and spatial variability of intertidal communities coincide with major biogeographical boundaries, areas where extensive compositional changes in the biota are observed over a limited geographic extension. We then investigate whether spatial variation in the biomass of functional groups, over geographic (10′s km) and local (10′s m) scales, could be associated to species diversity within and among these groups. Functional community structure expressed as abundance (density, cover and biomass) and composition of major functional groups was quantified through field surveys at 20 rocky intertidal shores spanning six degrees of latitude along the southwest Atlantic coast of Argentina and extending across the boundaries between the Argentinean and Magellanic Provinces. Patterns of abundance of individual functional groups were not uniformly matched with biogeographical regions. Only ephemeral algae showed an abrupt geographical discontinuity coincident with changes in biogeographic boundaries, and this was limited to the mid intertidal zone. We identified 3–4 main ‘groups’ of sites in terms of the total and relative abundance of the major functional groups, but these did not coincide with biogeographical boundaries, nor did they follow latitudinal arrangement. Thus, processes that determine the functional structure of these intertidal communities are insensitive to biogeographical boundaries. Over both geographical and local spatial scales, and for most functional groups and tidal levels, increases in species richness within the functional group was significantly associated to increased total biomass and reduced spatial variability of the group. These results suggest that species belonging to the same functional group are sufficiently uncorrelated over space (i.e. metres and site-to-site ) to stabilize patterns of biomass variability and, in this manner, provide a buffer, or “insurance”, against spatial variability in environmental conditions.
- Full Text:
- Authors: Wieters, Evie A , McQuaid, Christopher D , Palomo, Gabriela , Pappalardo, Paula
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6835 , http://hdl.handle.net/10962/d1010956
- Description: We investigate the extent to which functional structure and spatial variability of intertidal communities coincide with major biogeographical boundaries, areas where extensive compositional changes in the biota are observed over a limited geographic extension. We then investigate whether spatial variation in the biomass of functional groups, over geographic (10′s km) and local (10′s m) scales, could be associated to species diversity within and among these groups. Functional community structure expressed as abundance (density, cover and biomass) and composition of major functional groups was quantified through field surveys at 20 rocky intertidal shores spanning six degrees of latitude along the southwest Atlantic coast of Argentina and extending across the boundaries between the Argentinean and Magellanic Provinces. Patterns of abundance of individual functional groups were not uniformly matched with biogeographical regions. Only ephemeral algae showed an abrupt geographical discontinuity coincident with changes in biogeographic boundaries, and this was limited to the mid intertidal zone. We identified 3–4 main ‘groups’ of sites in terms of the total and relative abundance of the major functional groups, but these did not coincide with biogeographical boundaries, nor did they follow latitudinal arrangement. Thus, processes that determine the functional structure of these intertidal communities are insensitive to biogeographical boundaries. Over both geographical and local spatial scales, and for most functional groups and tidal levels, increases in species richness within the functional group was significantly associated to increased total biomass and reduced spatial variability of the group. These results suggest that species belonging to the same functional group are sufficiently uncorrelated over space (i.e. metres and site-to-site ) to stabilize patterns of biomass variability and, in this manner, provide a buffer, or “insurance”, against spatial variability in environmental conditions.
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Environmental domains and range-limiting mechanisms: testing the Abundant Centre Hypothesis using southern African sandhoppers
- Baldanzi, Simone, McQuaid, Christopher D, Cannicci, Stefano, Porri, Francesca
- Authors: Baldanzi, Simone , McQuaid, Christopher D , Cannicci, Stefano , Porri, Francesca
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6848 , http://hdl.handle.net/10962/d1011108
- Description: Predicting shifts of species geographical ranges is a fundamental challenge for conservation ecologists given the great complexity of factors involved in setting range limits. Distributional patterns are frequently modelled to “simplify” species responses to the environment, yet the central mechanisms that drive a particular pattern are rarely understood. We evaluated the distributions of two sandhopper species (Crustacea, Amphipoda, Talitridae), Talorchestia capensis and Africorchestia quadrispinosa along the Namibian and South African coasts, encompassing three biogeographic regions influenced by two different oceanographic systems, the Benguela and Agulhas currents. We aimed to test whether the Abundant Centre Hypothesis (ACH) can explain the distributions of these species’ abundances, sizes and sex ratios and examined which environmental parameters influence/drive these distributions. Animals were collected during a once-off survey at 29 sites over c.3500 km of coastline. The ACH was tested using a non-parametric constraint space analysis of the goodness of fit of five hypothetical models. Distance Based Linear Modelling (DistLM) was performed to evaluate which environmental traits influenced the distribution data. Abundance, size and sex ratio showed different patterns of distribution. A ramped model fitted the abundance (Ramped North) and size (Ramped South) distribution for A. quadrispinosa. The Inverse Quadratic model fitted the size distribution of T. capensis. Beach slope, salinity, sand temperature and percentage of detritus found on the shore at the time of collection played important roles in driving the abundance of A. quadrispinosa. T. capensis was mainly affected by salinity and the morphodynamic state of the beach. Our results provided only some support for the ACH predictions. The DistLM confirmed that the physical state of the beach is an important factor for sandy beach organisms. The effect of salinity and temperature suggest metabolic responses to local conditions and a role in small to mesoscale shifts in the range of these populations.
- Full Text:
- Authors: Baldanzi, Simone , McQuaid, Christopher D , Cannicci, Stefano , Porri, Francesca
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6848 , http://hdl.handle.net/10962/d1011108
- Description: Predicting shifts of species geographical ranges is a fundamental challenge for conservation ecologists given the great complexity of factors involved in setting range limits. Distributional patterns are frequently modelled to “simplify” species responses to the environment, yet the central mechanisms that drive a particular pattern are rarely understood. We evaluated the distributions of two sandhopper species (Crustacea, Amphipoda, Talitridae), Talorchestia capensis and Africorchestia quadrispinosa along the Namibian and South African coasts, encompassing three biogeographic regions influenced by two different oceanographic systems, the Benguela and Agulhas currents. We aimed to test whether the Abundant Centre Hypothesis (ACH) can explain the distributions of these species’ abundances, sizes and sex ratios and examined which environmental parameters influence/drive these distributions. Animals were collected during a once-off survey at 29 sites over c.3500 km of coastline. The ACH was tested using a non-parametric constraint space analysis of the goodness of fit of five hypothetical models. Distance Based Linear Modelling (DistLM) was performed to evaluate which environmental traits influenced the distribution data. Abundance, size and sex ratio showed different patterns of distribution. A ramped model fitted the abundance (Ramped North) and size (Ramped South) distribution for A. quadrispinosa. The Inverse Quadratic model fitted the size distribution of T. capensis. Beach slope, salinity, sand temperature and percentage of detritus found on the shore at the time of collection played important roles in driving the abundance of A. quadrispinosa. T. capensis was mainly affected by salinity and the morphodynamic state of the beach. Our results provided only some support for the ACH predictions. The DistLM confirmed that the physical state of the beach is an important factor for sandy beach organisms. The effect of salinity and temperature suggest metabolic responses to local conditions and a role in small to mesoscale shifts in the range of these populations.
- Full Text:
Stable isotope analysis indicates a lack of inter-and intra-specific dietary redundancy among ecologically important coral reef fishes
- Plass-Johnson, Jeremiah G, McQuaid, Christopher D, Hill, Jaclyn M
- Authors: Plass-Johnson, Jeremiah G , McQuaid, Christopher D , Hill, Jaclyn M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444611 , vital:74254 , https://doi.org/10.1007/s00338-012-0988-7
- Description: Parrotfish are critical consumers on coral reefs, mediating the balance between algae and corals, and are often categorised into three functional groups based on adult morphology and feeding behaviour. We used stable isotope analysis (δ13C, δ15N) to investigate size-related ontogenetic dietary changes in multiple species of parrotfish on coral reefs around Zanzibar. We compared signatures among species and functional groups (scrapers, excavators and browsers) as well as ontogenetic stages (immature, initial and terminal phase) within species. Stable isotope analysis suggests that ontogenetic dietary shifts occurred in seven of the nine species examined; larger individuals had enriched δ13C values, with no relationship between size and δ15N. The relationship between fish length and δ13C signature was maintained when species were categorised as scrapers and excavators, but was more pronounced for scrapers than excavators, indicating stronger ontogenetic changes. Isotopic mixing models classified the initial phase of both the most abundant excavator (Chlorurus sordidus) as a scraper and the immature stage of the scraper Scarus ghobban (the largest species) as an excavator, indicating that diet relates to size rather than taxonomy. The results indicate that parrotfish may show similar intra-group changes in diet with length, but that their trophic ecology is more complex than suggested by morphology alone. Stable isotope analyses indicate that feeding ecology may differ among species within functional groups, and according to ontogenetic stage within a species.
- Full Text:
- Authors: Plass-Johnson, Jeremiah G , McQuaid, Christopher D , Hill, Jaclyn M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444611 , vital:74254 , https://doi.org/10.1007/s00338-012-0988-7
- Description: Parrotfish are critical consumers on coral reefs, mediating the balance between algae and corals, and are often categorised into three functional groups based on adult morphology and feeding behaviour. We used stable isotope analysis (δ13C, δ15N) to investigate size-related ontogenetic dietary changes in multiple species of parrotfish on coral reefs around Zanzibar. We compared signatures among species and functional groups (scrapers, excavators and browsers) as well as ontogenetic stages (immature, initial and terminal phase) within species. Stable isotope analysis suggests that ontogenetic dietary shifts occurred in seven of the nine species examined; larger individuals had enriched δ13C values, with no relationship between size and δ15N. The relationship between fish length and δ13C signature was maintained when species were categorised as scrapers and excavators, but was more pronounced for scrapers than excavators, indicating stronger ontogenetic changes. Isotopic mixing models classified the initial phase of both the most abundant excavator (Chlorurus sordidus) as a scraper and the immature stage of the scraper Scarus ghobban (the largest species) as an excavator, indicating that diet relates to size rather than taxonomy. The results indicate that parrotfish may show similar intra-group changes in diet with length, but that their trophic ecology is more complex than suggested by morphology alone. Stable isotope analyses indicate that feeding ecology may differ among species within functional groups, and according to ontogenetic stage within a species.
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Effects of patch-size on populations of intertidal limpets, Siphonaria spp., in a linear landscape
- Cole, Victoria J, Johnson, Linda G, McQuaid, Christopher D
- Authors: Cole, Victoria J , Johnson, Linda G , McQuaid, Christopher D
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6845 , http://hdl.handle.net/10962/d1011050
- Description: Organisms with different life-histories and abilities to disperse often utilise habitat patches in different ways. We investigated the influence of the size of patches of rock (separated by stretches of sand) on the density of pulmonate limpets (Siphonaria spp.) along 1500 km of the linear landscape of the South African coastline. We compared the influence of patch-size on two congeneric species with different modes of development, S. serrata a direct developer, and S. concinna a planktonic developer. We tested the spatial and temporal consistency of the effects of patch-size by sampling 7 independent regions spanning the distributional range of both species of limpets, and by sampling one region at monthly intervals for 1 year. Within each region or month, 4 small patches (<20 m in length) interspersed with the 4 large patches (>60 m in length) were sampled. Across the entire geographic range and throughout the year, there were more of both species of limpets in large patches than in small patches. In most regions, there was greater variability in large patches than small patches. Variability within patches in a single region was similar throughout the year, with greater variability of both species in large than in small patches. We found little influence of the mode of development on the response of limpets to patch-size. Our findings highlight the importance of understanding patterns of distribution of species with respect to habitat heterogeneity in linear landscapes, and contradict the idea that organism mobility at an early ontogenetic stage directly affects habitat use.
- Full Text:
- Authors: Cole, Victoria J , Johnson, Linda G , McQuaid, Christopher D
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6845 , http://hdl.handle.net/10962/d1011050
- Description: Organisms with different life-histories and abilities to disperse often utilise habitat patches in different ways. We investigated the influence of the size of patches of rock (separated by stretches of sand) on the density of pulmonate limpets (Siphonaria spp.) along 1500 km of the linear landscape of the South African coastline. We compared the influence of patch-size on two congeneric species with different modes of development, S. serrata a direct developer, and S. concinna a planktonic developer. We tested the spatial and temporal consistency of the effects of patch-size by sampling 7 independent regions spanning the distributional range of both species of limpets, and by sampling one region at monthly intervals for 1 year. Within each region or month, 4 small patches (<20 m in length) interspersed with the 4 large patches (>60 m in length) were sampled. Across the entire geographic range and throughout the year, there were more of both species of limpets in large patches than in small patches. In most regions, there was greater variability in large patches than small patches. Variability within patches in a single region was similar throughout the year, with greater variability of both species in large than in small patches. We found little influence of the mode of development on the response of limpets to patch-size. Our findings highlight the importance of understanding patterns of distribution of species with respect to habitat heterogeneity in linear landscapes, and contradict the idea that organism mobility at an early ontogenetic stage directly affects habitat use.
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Love thy neighbour : group properties of gaping behaviour in mussel aggregations
- Nicastro, Katy R, Zardi, Gerardo I, McQuaid, Christopher D, Pearson, Gareth A, Serrão, Ester A
- Authors: Nicastro, Katy R , Zardi, Gerardo I , McQuaid, Christopher D , Pearson, Gareth A , Serrão, Ester A
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6841 , http://hdl.handle.net/10962/d1010991
- Description: By associating closely with others to form a group, an animal can benefit from a number of advantages including reduced risk of predation, amelioration of environmental conditions, and increased reproductive success, but at the price of reduced resources. Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism. Here we show that very simple behaviour in intertidal mussels shows new effects in dense aggregations but not in isolated individuals. Perna perna and Mytilus galloprovincialis are gaping (periodic valve movement during emersion) and non-gaping mussels respectively. P. perna gaping behaviour had no effect on body temperatures of isolated individuals, while it led to increased humidity and decreased temperatures in dense groups (beds). Gaping resulted in cooler body temperatures for P. perna than M. galloprovincialis when in aggregations, while solitary individuals exhibited the highest temperatures. Gradients of increasing body temperature were detected from the center to edges of beds, but M. galloprovincialis at the edge had the same temperature as isolated individuals. Furthermore, a field study showed that during periods of severe heat stress, mortality rates of mussels within beds of the gaping P. perna were lower than those of isolated individuals or within beds of M. galloprovincialis, highlighting the determinant role of gaping on fitness and group functioning. We demonstrate that new effects of very simple individual behaviour lead to amelioration of abiotic conditions at the aggregation level and that these effects increase mussel resistance to thermal stress.
- Full Text:
- Authors: Nicastro, Katy R , Zardi, Gerardo I , McQuaid, Christopher D , Pearson, Gareth A , Serrão, Ester A
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6841 , http://hdl.handle.net/10962/d1010991
- Description: By associating closely with others to form a group, an animal can benefit from a number of advantages including reduced risk of predation, amelioration of environmental conditions, and increased reproductive success, but at the price of reduced resources. Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism. Here we show that very simple behaviour in intertidal mussels shows new effects in dense aggregations but not in isolated individuals. Perna perna and Mytilus galloprovincialis are gaping (periodic valve movement during emersion) and non-gaping mussels respectively. P. perna gaping behaviour had no effect on body temperatures of isolated individuals, while it led to increased humidity and decreased temperatures in dense groups (beds). Gaping resulted in cooler body temperatures for P. perna than M. galloprovincialis when in aggregations, while solitary individuals exhibited the highest temperatures. Gradients of increasing body temperature were detected from the center to edges of beds, but M. galloprovincialis at the edge had the same temperature as isolated individuals. Furthermore, a field study showed that during periods of severe heat stress, mortality rates of mussels within beds of the gaping P. perna were lower than those of isolated individuals or within beds of M. galloprovincialis, highlighting the determinant role of gaping on fitness and group functioning. We demonstrate that new effects of very simple individual behaviour lead to amelioration of abiotic conditions at the aggregation level and that these effects increase mussel resistance to thermal stress.
- Full Text:
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.
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Associations in ephemeral systems: the lack of trophic relationships between sandhoppers and beach wrack
- Porri, Francesca, Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Porri, Francesca , Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444552 , vital:74250 , https://doi.org/10.3354/meps08951
- Description: In ephemeral systems, material subsidies can play a key role in the persistence and connectivity of populations, especially if the organisms living within them are trophically dependent on imported resources. Sandy beaches are heavily subsidized by organic material of both terrestrial and marine origin. For highly mobile supratidal fringe species, such as amphipods, which are marine but with a high tolerance of aerial conditions, such material potentially provides both food and shelter. We investigated the relationship between beach wrack and amphipods by examining the trophic contribution of allochthonous food sources to sandhopper diets using stable isotope analysis. Replicate samples of the sandhopper Talorchestia capensis and several types of beach wrack (including seagrass, wood and different macrophytes) colonized by these amphipods were collected from 11 sites within one biogeographical region along the south coast of South Africa.
- Full Text:
- Authors: Porri, Francesca , Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444552 , vital:74250 , https://doi.org/10.3354/meps08951
- Description: In ephemeral systems, material subsidies can play a key role in the persistence and connectivity of populations, especially if the organisms living within them are trophically dependent on imported resources. Sandy beaches are heavily subsidized by organic material of both terrestrial and marine origin. For highly mobile supratidal fringe species, such as amphipods, which are marine but with a high tolerance of aerial conditions, such material potentially provides both food and shelter. We investigated the relationship between beach wrack and amphipods by examining the trophic contribution of allochthonous food sources to sandhopper diets using stable isotope analysis. Replicate samples of the sandhopper Talorchestia capensis and several types of beach wrack (including seagrass, wood and different macrophytes) colonized by these amphipods were collected from 11 sites within one biogeographical region along the south coast of South Africa.
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Geographic variation in the trophic ecology of an avian rocky shore predator, the African black oystercatcher, along the southern African coastline
- Kohler, Sophie A, Connan, Maëlle, Hill, Jaclyn M, Mablouké, Cécile, Bonnevie, Bo T, Ludynia, Katrin, Kemper, Jessica, Huisamen, Johan, Underhill, Leslie G, Cherel, Yves, McQuaid, Christopher D, Jaquemet, Sébastien
- Authors: Kohler, Sophie A , Connan, Maëlle , Hill, Jaclyn M , Mablouké, Cécile , Bonnevie, Bo T , Ludynia, Katrin , Kemper, Jessica , Huisamen, Johan , Underhill, Leslie G , Cherel, Yves , McQuaid, Christopher D , Jaquemet, Sébastien
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444576 , vital:74252 , https://doi.org/10.3354/meps09215
- Description: The reflection of baseline isotopic signals along marine food chains up to higher trophic levels has been widely used in the study of oceanic top predators but rarely for intertidal predators. We investigated variation in the δ 13 C and δ 15 N ratios of a sedentary, rocky shore predator, the African black oystercatcher Haematopus moquini, over~ 2000 km of the southern African coastline, which is characterized by strong biogeographic patterns in primary productivity and intertidal communities. Blood and feathers from breeding adults and chicks and muscle tissues from primary prey items (mussels and limpets) were sampled between southern Namibia and the southeast coast of South Africa. 15 N enrichment was observed between the southeast and west coasts in oystercatcher tissues and their prey, mirroring an isotope shift between the oligotrophic Agulhas Current on the east coast and the eutrophic Benguela upwelling system on the west coast.
- Full Text:
- Authors: Kohler, Sophie A , Connan, Maëlle , Hill, Jaclyn M , Mablouké, Cécile , Bonnevie, Bo T , Ludynia, Katrin , Kemper, Jessica , Huisamen, Johan , Underhill, Leslie G , Cherel, Yves , McQuaid, Christopher D , Jaquemet, Sébastien
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444576 , vital:74252 , https://doi.org/10.3354/meps09215
- Description: The reflection of baseline isotopic signals along marine food chains up to higher trophic levels has been widely used in the study of oceanic top predators but rarely for intertidal predators. We investigated variation in the δ 13 C and δ 15 N ratios of a sedentary, rocky shore predator, the African black oystercatcher Haematopus moquini, over~ 2000 km of the southern African coastline, which is characterized by strong biogeographic patterns in primary productivity and intertidal communities. Blood and feathers from breeding adults and chicks and muscle tissues from primary prey items (mussels and limpets) were sampled between southern Namibia and the southeast coast of South Africa. 15 N enrichment was observed between the southeast and west coasts in oystercatcher tissues and their prey, mirroring an isotope shift between the oligotrophic Agulhas Current on the east coast and the eutrophic Benguela upwelling system on the west coast.
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Stable isotope methods: the effect of gut contents on isotopic ratios of zooplankton
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444623 , vital:74255 , https://doi.org/10.1016/j.ecss.2011.02.002
- Description: In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the δ13C and δ15N ratios of three size classes of zooplankton (1.0–2.0, 2.0–4.0 and >4.0mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444623 , vital:74255 , https://doi.org/10.1016/j.ecss.2011.02.002
- Description: In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the δ13C and δ15N ratios of three size classes of zooplankton (1.0–2.0, 2.0–4.0 and >4.0mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations.
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First oceanographic survey of the entire continental shelf adjacent to the northern Agulhas Current
- Lutjeharms, Johan R E, Durgadoo, Jonathan V, Schapira, Mathilde, McQuaid, Christopher D
- Authors: Lutjeharms, Johan R E , Durgadoo, Jonathan V , Schapira, Mathilde , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6867 , http://hdl.handle.net/10962/d1011499 , http://www.sajs.co.za/index.php/SAJS/article/view/410
- Description: [from introduction] The Agulhas Current is by far the largest western boundary current of the southern hemisphere1 and carries about 70 × 106 m3/s of seawater past the eastern shores of South Africa.2 Being more than 2000 m deep, it follows the continental shelf edge quite closely. Its northern part, all the way downstream to Algoa Bay, has a very stable trajectory whereas the southern part meanders widely to either side of a mean geographical location,3 in the process creating shear edge eddies and attendant plumes of warm surface water over the shelf.4 However, the direct influence of the Agulhas Current on the waters and ecosystems of the adjacent shelf of South Africa remains largely unknown.
- Full Text:
- Authors: Lutjeharms, Johan R E , Durgadoo, Jonathan V , Schapira, Mathilde , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6867 , http://hdl.handle.net/10962/d1011499 , http://www.sajs.co.za/index.php/SAJS/article/view/410
- Description: [from introduction] The Agulhas Current is by far the largest western boundary current of the southern hemisphere1 and carries about 70 × 106 m3/s of seawater past the eastern shores of South Africa.2 Being more than 2000 m deep, it follows the continental shelf edge quite closely. Its northern part, all the way downstream to Algoa Bay, has a very stable trajectory whereas the southern part meanders widely to either side of a mean geographical location,3 in the process creating shear edge eddies and attendant plumes of warm surface water over the shelf.4 However, the direct influence of the Agulhas Current on the waters and ecosystems of the adjacent shelf of South Africa remains largely unknown.
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Mechanisms of habitat segregation between an invasive (Mytilus galloprovincialis) and an indigenous (Perna perna) mussel: adult growth and mortality
- Bownes, Sarah J, McQuaid, Christopher D
- Authors: Bownes, Sarah J , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6868 , http://hdl.handle.net/10962/d1011500
- Description: The invasive mussel Mytilus galloprovincialis and the indigenous mussel Perna perna coexist intertidally on the south coast of South Africa through partial vertical habitat segregation: M. galloprovincialis dominates the upper shore and P. perna the lower shore. Recruitment patterns can explain the zonation of P. perna, but not the invasive species. We examined the role of post-recruitment interactions by measuring spatial and temporal differences in adult growth and mortality rates of the two species. Specifically, we tested the hypothesis that interspecific differences in growth and mortality reflect adult distribution patterns. The two study locations, Plettenberg Bay and Tsitsikamma, are 70 km apart with two sites (separated by 300–400 m) per location, each divided into three vertical zones. Growth was measured seasonally using different marking methods in 2001 and 2003. Cumulative adult mortality was measured through summer in 2003/2004. Both species generally grew more slowly upshore, but they showed different effects of season. For P. perna, growth was significantly reduced in winter in the low zone, but unaffected by season in the high zone. For M. galloprovincialis, growth was either unaffected by season or increased in winter, even in the high zone. Thus, growth of P. perna and M. galloprovincialis was reduced under cool winter and warm summer temperatures, respectively; and while growth was more similar between species in summer, M. galloprovincialis grew much faster than P. perna in winter. Mortality of P. perna increased upshore. For M. galloprovincialis, mortality was not zone-dependent and was significantly greater than for P. perna on the low-shore and (generally) across the shore in Tsitsikamma. Both species had higher growth and mortality rates in Plettenberg Bay than in Tsitsikamma. Thus, P. perna seems able to maintain spatial dominance on the low-shore and at certain sites because of higher mortality of M. galloprovincialis. We conclude that seasonality in growth of the two species reflects their biogeographic affinities and that coexistence is possible through pre-recruitment effects that limit the vertical distribution of P. perna and post-recruitment effects that limit M. galloprovincialis.
- Full Text:
- Authors: Bownes, Sarah J , McQuaid, Christopher D
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6868 , http://hdl.handle.net/10962/d1011500
- Description: The invasive mussel Mytilus galloprovincialis and the indigenous mussel Perna perna coexist intertidally on the south coast of South Africa through partial vertical habitat segregation: M. galloprovincialis dominates the upper shore and P. perna the lower shore. Recruitment patterns can explain the zonation of P. perna, but not the invasive species. We examined the role of post-recruitment interactions by measuring spatial and temporal differences in adult growth and mortality rates of the two species. Specifically, we tested the hypothesis that interspecific differences in growth and mortality reflect adult distribution patterns. The two study locations, Plettenberg Bay and Tsitsikamma, are 70 km apart with two sites (separated by 300–400 m) per location, each divided into three vertical zones. Growth was measured seasonally using different marking methods in 2001 and 2003. Cumulative adult mortality was measured through summer in 2003/2004. Both species generally grew more slowly upshore, but they showed different effects of season. For P. perna, growth was significantly reduced in winter in the low zone, but unaffected by season in the high zone. For M. galloprovincialis, growth was either unaffected by season or increased in winter, even in the high zone. Thus, growth of P. perna and M. galloprovincialis was reduced under cool winter and warm summer temperatures, respectively; and while growth was more similar between species in summer, M. galloprovincialis grew much faster than P. perna in winter. Mortality of P. perna increased upshore. For M. galloprovincialis, mortality was not zone-dependent and was significantly greater than for P. perna on the low-shore and (generally) across the shore in Tsitsikamma. Both species had higher growth and mortality rates in Plettenberg Bay than in Tsitsikamma. Thus, P. perna seems able to maintain spatial dominance on the low-shore and at certain sites because of higher mortality of M. galloprovincialis. We conclude that seasonality in growth of the two species reflects their biogeographic affinities and that coexistence is possible through pre-recruitment effects that limit the vertical distribution of P. perna and post-recruitment effects that limit M. galloprovincialis.
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Effects of food quality on tissue-specific isotope ratios in the mussel Perna perna
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444563 , vital:74251 , https://doi.org/10.1007/s10750-009-9865-y
- Description: Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis. The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444563 , vital:74251 , https://doi.org/10.1007/s10750-009-9865-y
- Description: Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis. The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months.
- 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.
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Variability in the fractionation of stable isotopes during degradation of two intertidal red algae
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444649 , vital:74257 , https://doi.org/10.1016/j.ecss.2009.02.001
- Description: Macroalgae contribute to intertidal food webs primarily as detritus, with unclear implications for food web studies using stable isotope analysis. We examined differences in the thallus parts of two South African rhodophytes (Gelidium pristoides and Hypnea spicifera) and changes in overall δ13C, δ15N signatures and C:N ratios during degradation in both the field and laboratory. We hypothesized that both degrading macroalgal tissue and macroalgal-derived suspended particulate material (SPM) would show negligible changes in δ13C, but enriched δ15N signatures and lower C:N ratios relative to healthy plants. Only C:N laboratory ratios conformed to predictions, with both species of macroalgae showing decomposition related changes in δ13C and significant depletions in δ15N in both the field and laboratory. In the laboratory, algal tissue and SPM from each species behaved similarly (though some effects were non-significant) but with differing strengths. Gelidium pristoides δ13C increased and C:N ratios decreased over time in tissue and SPM; δ15N became depleted only in SPM. Hypnea spicifera, δ13C, δ15N and C:N ratios all decreased during degradation in both SPM and algae.
- Full Text:
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444649 , vital:74257 , https://doi.org/10.1016/j.ecss.2009.02.001
- Description: Macroalgae contribute to intertidal food webs primarily as detritus, with unclear implications for food web studies using stable isotope analysis. We examined differences in the thallus parts of two South African rhodophytes (Gelidium pristoides and Hypnea spicifera) and changes in overall δ13C, δ15N signatures and C:N ratios during degradation in both the field and laboratory. We hypothesized that both degrading macroalgal tissue and macroalgal-derived suspended particulate material (SPM) would show negligible changes in δ13C, but enriched δ15N signatures and lower C:N ratios relative to healthy plants. Only C:N laboratory ratios conformed to predictions, with both species of macroalgae showing decomposition related changes in δ13C and significant depletions in δ15N in both the field and laboratory. In the laboratory, algal tissue and SPM from each species behaved similarly (though some effects were non-significant) but with differing strengths. Gelidium pristoides δ13C increased and C:N ratios decreased over time in tissue and SPM; δ15N became depleted only in SPM. Hypnea spicifera, δ13C, δ15N and C:N ratios all decreased during degradation in both SPM and algae.
- Full Text: