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Raymond D. Semlitsch - One of the best experts on this subject based on the ideXlab platform.
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Intermorph breeding and the potential for reproductive isolation in polymorphic Mole Salamanders (Ambystoma talpoideum)
Behavioral Ecology and Sociobiology, 2006Co-Authors: Howard H Whiteman, John D. Krenz, Raymond D. SemlitschAbstract:The study of reproductive isolation as a prerequisite to sympatric speciation has been limited by the focus on species that have already experienced such isolation. However, a complete understanding of how such processes evolve depends on observing taxa before they complete the speciation process. We studied the potential for sexual isolation in the polyphenic Mole Salamander, Ambystoma talpoideum , using a series of laboratory and field experiments. This species consists of aquatic paedomorphic adults and terrestrial metamorphic adults which are exhibited by both sexes and which mate in the same aquatic habitat. Previous field studies on this species suggested that intermorph breeding would be less common during the winter months, because paedomorphic adults begin breeding in early autumn and thus may have less energy available for reproduction in the winter. Laboratory experiments conducted during the winter showed that the mating behavior of paedomorphic males occurred at a much lower frequency than that of metamorphic males. In contrast, field experiments that best mimicked natural conditions revealed symmetric intermorph breeding and included multiple paternity shared among males of each morph. This and other studies suggest that there is little evidence of sexual isolation among morphs based on behavioral interactions alone. However, the potential for partial isolation still occurs because of temporal and spatial differences in the frequencies of each morph in nature. Our results suggest that further studies on this system, and other similar polyphenisms, may provide valuable insight into the mechanisms that underlie the evolution of reproductive isolation.
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Asymmetric reproductive isolation among polymorphic Salamanders
Biological Journal of the Linnean Society, 2005Co-Authors: Howard H Whiteman, Raymond D. SemlitschAbstract:The study of reproductive isolation (RI) as a prerequisite to sympatric speciation has been limited by a focus on species that have already experienced isolation. However, a complete understanding of speciation depends on observing taxa before they complete the speciation process. We estimated RI in field populations of the polyphenic Mole Salamander, Ambystoma talpoideum, by capturing paedomorphic (aquatic) and metamorphic (terrestrial) adults during the breeding season from two natural populations. We found evidence for asymmetric RI between morphs, such that paedomorphic males and metamorphic females had functionally zero RI, whereas metamorphic males and paedomorphic females had substantial RI. Evidence suggests that ecological factors such as the abundance of each morph, timing of rainfall, and water depth of the breeding habitat play a large role in the production of these asymmetries. Spatial aspects of RI had a greater relative impact on overall isolation than temporal differences, in part because metamorphic adults were often captured in shallower water than paedomorphic adults. However, morph separation varied across populations and year, suggesting that environmental heterogeneity likely plays a large role in the potential for RI, particularly between metamorphic males and paedomorphic females. In addition, body-size variation and behavioural differences could also influence the RI estimates presented here. Although facultative paedomorphosis appears to have played a large role in macroevolutionary change via allopatric speciation in some taxa, our results suggest that there is little potential for sympatric speciation in the future within these populations. However, asymmetric RI creates the opportunity for fitness differences between morphs and sexes that would directly affect the maintenance of this polymorphism. Our results suggest that further studies on this and other polyphenisms may provide valuable insight into the evolution of RI and the role of environmental heterogeneity in the production and maintenance of biological diversity. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86, 265−281.
Mary E. Brown - One of the best experts on this subject based on the ideXlab platform.
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Life history plasticity does not confer resilience to environmental change in the Mole Salamander (Ambystoma talpoideum)
Oecologia, 2017Co-Authors: Courtney L. Davis, David A.w. Miller, Susan C. Walls, William J. Barichivich, Jeffrey Riley, Mary E. BrownAbstract:Plasticity in life history strategies can be advantageous for species that occupy spatially or temporally variable environments. We examined how phenotypic plasticity influences responses of the Mole Salamander, Ambystoma talpoideum , to disturbance events at the St. Marks National Wildlife Refuge (SMNWR), FL, USA from 2009 to 2014. We observed periods of extensive drought early in the study, in contrast to high rainfall and expansive flooding events in later years. Flooding facilitated colonization of predatory fishes to isolated wetlands across the refuge. We employed multistate occupancy models to determine how this natural experiment influenced the occurrence of aquatic larvae and paedomorphic adults and what implications this may have for the population. We found that, in terms of occurrence, responses to environmental variation differed between larvae and paedomorphs, but plasticity (i.e. the ability to metamorphose rather than remain in aquatic environment) was not sufficient to buffer populations from declining as a result of environmental perturbations. Drought and fish presence negatively influenced occurrence dynamics of larval and paedomorphic Mole Salamanders and, consequently, contributed to observed short-term declines of this species. Overall occurrence of larval Salamanders decreased from 0.611 in 2009 to 0.075 in 2014 and paedomorph occurrence decreased from 0.311 in 2009 to 0.121 in 2014. Although variation in selection pressures has likely maintained this polyphenism previously, our results suggest that continued changes in environmental variability and the persistence of fish in isolated wetlands could lead to a loss of paedomorphosis in the SMNWR population and, ultimately, impact regional persistence in the future.
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Species interactions and the effects of climate variability on a wetland amphibian metacommunity
Ecological applications : a publication of the Ecological Society of America, 2017Co-Authors: Courtney L. Davis, David A.w. Miller, Susan C. Walls, William J. Barichivich, Jeffrey W. Riley, Mary E. BrownAbstract:Disentangling the role that multiple interacting factors have on species responses to shifting climate poses a significant challenge. However, our ability to do so is of utmost importance to predict the effects of climate change on species distributions. We examined how populations of three species of wetland breeding amphibians, which varied in life history requirements, responded to a six-year period of extremely variable in precipitation. This interval was punctuated by both extensive drought and heavy precipitation and flooding, providing a natural experiment to measure community responses to environmental perturbations. We estimated occurrence dynamics using a discrete hidden Markov modeling approach that incorporated information regarding habitat state and predator-prey interactions. This approach allowed us to measure how metapopulation dynamics of each amphibian species was affected by interactions among weather, wetland hydroperiod, and co-occurrence with fish predators. The pig frog, a generalist, proved most resistant to perturbations, with both colonization and persistence being unaffected by seasonal variation in precipitation or co-occurrence with fishes. The ornate chorus frog, an ephemeral wetland specialist, responded positively to periods of drought owing to increased persistence and colonization rates during periods of low-rainfall. Low probabilities of occurrence of the ornate chorus frog in long-duration wetlands were driven by interactions with predators due to low colonization rates when fishes were present. The Mole Salamander was most sensitive to shifts in water availability. In our study area, this species never occurred in short-duration wetlands and persistence probabilities decreased during periods of drought. At the same time, negative effects occurred with extreme precipitation because flooding facilitated colonization of fishes to isolated wetlands and Mole Salamanders did not colonize wetlands once fishes were present. We demonstrate that the effects of changes in water availability depend on interactions with predators and wetland type and are influenced by the life history of each of our species. The dynamic species occurrence modeling approach we used offers promise for other systems when the goal is to disentangle the complex interactions that determine species responses to environmental variability. This article is protected by copyright. All rights reserved.
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Drought, deluge and declines: the impact of precipitation extremes on amphibians in a changing climate.
Biology, 2013Co-Authors: Susan C. Walls, William J. Barichivich, Mary E. BrownAbstract:The Class Amphibia is one of the most severely impacted taxa in an on-going global biodiversity crisis. Because amphibian reproduction is tightly associated with the presence of water, climatic changes that affect water availability pose a particularly menacing threat to both aquatic and terrestrial-breeding amphibians. We explore the impacts that one facet of climate change—that of extreme variation in precipitation—may have on amphibians. This variation is manifested principally as increases in the incidence and severity of both drought and major storm events. We stress the need to consider not only total precipitation amounts but also the pattern and timing of rainfall events. Such rainfall “pulses” are likely to become increasingly more influential on amphibians, especially in relation to seasonal reproduction. Changes in reproductive phenology can strongly influence the outcome of competitive and predatory interactions, thus potentially altering community dynamics in assemblages of co-existing species. We present a conceptual model to illustrate possible landscape and metapopulation consequences of alternative climate change scenarios for pond-breeding amphibians, using the Mole Salamander, Ambystoma talpoideum, as an example. Although amphibians have evolved a variety of life history strategies that enable them to cope with environmental uncertainty, it is unclear whether adaptations can keep pace with the escalating rate of climate change. Climate change, especially in combination with other stressors, is a daunting challenge for the persistence of amphibians and, thus, the conservation of global biodiversity.
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Influence of Drought on Salamander Occupancy of Isolated Wetlands on the Southeastern Coastal Plain of the United States
Wetlands, 2013Co-Authors: Susan C. Walls, William J. Barichivich, Mary E. Brown, David E. Scott, Blake R. HossackAbstract:In the southeastern U.S., changes in temperature and precipitation over the last three decades have been the most dramatic in winter and spring seasons. Continuation of these trends could negatively impact pond-breeding amphibians, especially those that rely on winter and spring rains to fill seasonal wetlands, trigger breeding, and ensure reproductive success. From 2009 to 2012, we monitored Spring and Fall presence of aquatic stages (larval and paedomorphic, gilled adult) of a winter-breeding amphibian (the Mole Salamander, Ambystoma talpoideum) and used multi-season models to estimate occupancy, local colonization and extinction. Seasonal estimates of occupancy, corrected for imperfect detection, declined from 22.3 % of ponds in Spring 2009 to 9.9 % in Fall 2012. Our best supported model suggested that changes in occupancy were driven by increased rates of extinction that corresponded with drought-related drying of ponds. Based on uncertainty in climate change projections for the Southeast, we present a conceptual model of predicted changes in wetland hydroperiods across a landscape with projected decreases and increases in future precipitation. Such precipitation changes could alter wetland hydroperiods, facilitate extinctions of species adapted to short, intermediate or long hydroperiod environments and, ultimately, modify the composition of amphibian communities within freshwater wetland ecosystems.
Susan C. Walls - One of the best experts on this subject based on the ideXlab platform.
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Life history plasticity does not confer resilience to environmental change in the Mole Salamander (Ambystoma talpoideum)
Oecologia, 2017Co-Authors: Courtney L. Davis, David A.w. Miller, Susan C. Walls, William J. Barichivich, Jeffrey Riley, Mary E. BrownAbstract:Plasticity in life history strategies can be advantageous for species that occupy spatially or temporally variable environments. We examined how phenotypic plasticity influences responses of the Mole Salamander, Ambystoma talpoideum , to disturbance events at the St. Marks National Wildlife Refuge (SMNWR), FL, USA from 2009 to 2014. We observed periods of extensive drought early in the study, in contrast to high rainfall and expansive flooding events in later years. Flooding facilitated colonization of predatory fishes to isolated wetlands across the refuge. We employed multistate occupancy models to determine how this natural experiment influenced the occurrence of aquatic larvae and paedomorphic adults and what implications this may have for the population. We found that, in terms of occurrence, responses to environmental variation differed between larvae and paedomorphs, but plasticity (i.e. the ability to metamorphose rather than remain in aquatic environment) was not sufficient to buffer populations from declining as a result of environmental perturbations. Drought and fish presence negatively influenced occurrence dynamics of larval and paedomorphic Mole Salamanders and, consequently, contributed to observed short-term declines of this species. Overall occurrence of larval Salamanders decreased from 0.611 in 2009 to 0.075 in 2014 and paedomorph occurrence decreased from 0.311 in 2009 to 0.121 in 2014. Although variation in selection pressures has likely maintained this polyphenism previously, our results suggest that continued changes in environmental variability and the persistence of fish in isolated wetlands could lead to a loss of paedomorphosis in the SMNWR population and, ultimately, impact regional persistence in the future.
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Species interactions and the effects of climate variability on a wetland amphibian metacommunity
Ecological applications : a publication of the Ecological Society of America, 2017Co-Authors: Courtney L. Davis, David A.w. Miller, Susan C. Walls, William J. Barichivich, Jeffrey W. Riley, Mary E. BrownAbstract:Disentangling the role that multiple interacting factors have on species responses to shifting climate poses a significant challenge. However, our ability to do so is of utmost importance to predict the effects of climate change on species distributions. We examined how populations of three species of wetland breeding amphibians, which varied in life history requirements, responded to a six-year period of extremely variable in precipitation. This interval was punctuated by both extensive drought and heavy precipitation and flooding, providing a natural experiment to measure community responses to environmental perturbations. We estimated occurrence dynamics using a discrete hidden Markov modeling approach that incorporated information regarding habitat state and predator-prey interactions. This approach allowed us to measure how metapopulation dynamics of each amphibian species was affected by interactions among weather, wetland hydroperiod, and co-occurrence with fish predators. The pig frog, a generalist, proved most resistant to perturbations, with both colonization and persistence being unaffected by seasonal variation in precipitation or co-occurrence with fishes. The ornate chorus frog, an ephemeral wetland specialist, responded positively to periods of drought owing to increased persistence and colonization rates during periods of low-rainfall. Low probabilities of occurrence of the ornate chorus frog in long-duration wetlands were driven by interactions with predators due to low colonization rates when fishes were present. The Mole Salamander was most sensitive to shifts in water availability. In our study area, this species never occurred in short-duration wetlands and persistence probabilities decreased during periods of drought. At the same time, negative effects occurred with extreme precipitation because flooding facilitated colonization of fishes to isolated wetlands and Mole Salamanders did not colonize wetlands once fishes were present. We demonstrate that the effects of changes in water availability depend on interactions with predators and wetland type and are influenced by the life history of each of our species. The dynamic species occurrence modeling approach we used offers promise for other systems when the goal is to disentangle the complex interactions that determine species responses to environmental variability. This article is protected by copyright. All rights reserved.
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Drought, deluge and declines: the impact of precipitation extremes on amphibians in a changing climate.
Biology, 2013Co-Authors: Susan C. Walls, William J. Barichivich, Mary E. BrownAbstract:The Class Amphibia is one of the most severely impacted taxa in an on-going global biodiversity crisis. Because amphibian reproduction is tightly associated with the presence of water, climatic changes that affect water availability pose a particularly menacing threat to both aquatic and terrestrial-breeding amphibians. We explore the impacts that one facet of climate change—that of extreme variation in precipitation—may have on amphibians. This variation is manifested principally as increases in the incidence and severity of both drought and major storm events. We stress the need to consider not only total precipitation amounts but also the pattern and timing of rainfall events. Such rainfall “pulses” are likely to become increasingly more influential on amphibians, especially in relation to seasonal reproduction. Changes in reproductive phenology can strongly influence the outcome of competitive and predatory interactions, thus potentially altering community dynamics in assemblages of co-existing species. We present a conceptual model to illustrate possible landscape and metapopulation consequences of alternative climate change scenarios for pond-breeding amphibians, using the Mole Salamander, Ambystoma talpoideum, as an example. Although amphibians have evolved a variety of life history strategies that enable them to cope with environmental uncertainty, it is unclear whether adaptations can keep pace with the escalating rate of climate change. Climate change, especially in combination with other stressors, is a daunting challenge for the persistence of amphibians and, thus, the conservation of global biodiversity.
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Influence of Drought on Salamander Occupancy of Isolated Wetlands on the Southeastern Coastal Plain of the United States
Wetlands, 2013Co-Authors: Susan C. Walls, William J. Barichivich, Mary E. Brown, David E. Scott, Blake R. HossackAbstract:In the southeastern U.S., changes in temperature and precipitation over the last three decades have been the most dramatic in winter and spring seasons. Continuation of these trends could negatively impact pond-breeding amphibians, especially those that rely on winter and spring rains to fill seasonal wetlands, trigger breeding, and ensure reproductive success. From 2009 to 2012, we monitored Spring and Fall presence of aquatic stages (larval and paedomorphic, gilled adult) of a winter-breeding amphibian (the Mole Salamander, Ambystoma talpoideum) and used multi-season models to estimate occupancy, local colonization and extinction. Seasonal estimates of occupancy, corrected for imperfect detection, declined from 22.3 % of ponds in Spring 2009 to 9.9 % in Fall 2012. Our best supported model suggested that changes in occupancy were driven by increased rates of extinction that corresponded with drought-related drying of ponds. Based on uncertainty in climate change projections for the Southeast, we present a conceptual model of predicted changes in wetland hydroperiods across a landscape with projected decreases and increases in future precipitation. Such precipitation changes could alter wetland hydroperiods, facilitate extinctions of species adapted to short, intermediate or long hydroperiod environments and, ultimately, modify the composition of amphibian communities within freshwater wetland ecosystems.
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Differences in foraging behaviour explain interspecific growth inhibition in competing Salamanders
Animal Behaviour, 1996Co-Authors: Susan C. WallsAbstract:Abstract Co-existence in a species-pair of pond-breeding Salamanders has been attributed to a trade-off in the competitive abilities of their larvae: the Mole Salamander,Ambystoma talpoideum, is aggressively superior to the spotted Salamander,A. maculatum. Conversely,A. maculatuminhibits the growth of both conspecifics andA. talpoideum, yet the mechanism of this growth inhibition is unknown. Interspecific variation in foraging behaviour was examined to test the hypothesis thatA. maculatumreduces the growth of competitors through its superior performance as a forager. In replicated trials, the behaviour of individual larvae was recorded as each foraged on a single type of prey,Daphnia pulex, provided at a constant density.A. maculatumwas exploitatively superior totalpoideum: larvae of the former species had significantly faster rates of prey capture than did their interspecific competitors. Moreover, relative to the behaviour ofA. talpoideum,A. maculatumlooked towards prey items at a significantly greater rate, spent a greater proportion of time in pursuit of prey and spent less time handling each prey item. These interspecific differences in foraging behaviour provide a mechanism by which larvae ofA. maculatummay inhibit the growth of competitors. The results support the hypothesis that exploitative superiority inA. maculatumcounteracts aggression byA. talpoideum, thus emphasizing the importance of ‘trade-offs’ in competitive abilities to co-existence in this species-pair.
Howard H Whiteman - One of the best experts on this subject based on the ideXlab platform.
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asymmetric effects of intra and interspecific competition on a pond breeding Salamander
Ecology, 2015Co-Authors: Thomas L Anderson, Howard H WhitemanAbstract:A fundamental goal of evolutionary ecology is to understand how asymmetric competition influences phenotype expression, yet few studies have quantified the relative effects of intra- and interspecific competition on phenotypes. We examined the effects of intra- and interspecific larval competition on both discrete and continuous phenotype expression of the facultatively paedomorphic Mole Salamander (Ambystoma talpoideum). We manipulated the density and frequency of larval A. talpoideum and a common competitor, the spotted Salamander (A. maculatum), in experimental mesocosms within a response surface design. The production of discrete ontogenetic morphs (metamorphs, paedomorphs, and overwintering larvae) was affected more by intraspecific than interspecific competition, but the effect varied between morphs. Paedomorph and metamorph production were more strongly affected by intraspecific than interspecific competition, while the production of overwintering larvae was affected by each type of competition app...
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Intermorph breeding and the potential for reproductive isolation in polymorphic Mole Salamanders (Ambystoma talpoideum)
Behavioral Ecology and Sociobiology, 2006Co-Authors: Howard H Whiteman, John D. Krenz, Raymond D. SemlitschAbstract:The study of reproductive isolation as a prerequisite to sympatric speciation has been limited by the focus on species that have already experienced such isolation. However, a complete understanding of how such processes evolve depends on observing taxa before they complete the speciation process. We studied the potential for sexual isolation in the polyphenic Mole Salamander, Ambystoma talpoideum , using a series of laboratory and field experiments. This species consists of aquatic paedomorphic adults and terrestrial metamorphic adults which are exhibited by both sexes and which mate in the same aquatic habitat. Previous field studies on this species suggested that intermorph breeding would be less common during the winter months, because paedomorphic adults begin breeding in early autumn and thus may have less energy available for reproduction in the winter. Laboratory experiments conducted during the winter showed that the mating behavior of paedomorphic males occurred at a much lower frequency than that of metamorphic males. In contrast, field experiments that best mimicked natural conditions revealed symmetric intermorph breeding and included multiple paternity shared among males of each morph. This and other studies suggest that there is little evidence of sexual isolation among morphs based on behavioral interactions alone. However, the potential for partial isolation still occurs because of temporal and spatial differences in the frequencies of each morph in nature. Our results suggest that further studies on this system, and other similar polyphenisms, may provide valuable insight into the mechanisms that underlie the evolution of reproductive isolation.
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Asymmetric reproductive isolation among polymorphic Salamanders
Biological Journal of the Linnean Society, 2005Co-Authors: Howard H Whiteman, Raymond D. SemlitschAbstract:The study of reproductive isolation (RI) as a prerequisite to sympatric speciation has been limited by a focus on species that have already experienced isolation. However, a complete understanding of speciation depends on observing taxa before they complete the speciation process. We estimated RI in field populations of the polyphenic Mole Salamander, Ambystoma talpoideum, by capturing paedomorphic (aquatic) and metamorphic (terrestrial) adults during the breeding season from two natural populations. We found evidence for asymmetric RI between morphs, such that paedomorphic males and metamorphic females had functionally zero RI, whereas metamorphic males and paedomorphic females had substantial RI. Evidence suggests that ecological factors such as the abundance of each morph, timing of rainfall, and water depth of the breeding habitat play a large role in the production of these asymmetries. Spatial aspects of RI had a greater relative impact on overall isolation than temporal differences, in part because metamorphic adults were often captured in shallower water than paedomorphic adults. However, morph separation varied across populations and year, suggesting that environmental heterogeneity likely plays a large role in the potential for RI, particularly between metamorphic males and paedomorphic females. In addition, body-size variation and behavioural differences could also influence the RI estimates presented here. Although facultative paedomorphosis appears to have played a large role in macroevolutionary change via allopatric speciation in some taxa, our results suggest that there is little potential for sympatric speciation in the future within these populations. However, asymmetric RI creates the opportunity for fitness differences between morphs and sexes that would directly affect the maintenance of this polymorphism. Our results suggest that further studies on this and other polyphenisms may provide valuable insight into the evolution of RI and the role of environmental heterogeneity in the production and maintenance of biological diversity. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86, 265−281.
Armando Sunny - One of the best experts on this subject based on the ideXlab platform.
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Genetic diversity and structure of two endangered Mole Salamander species of the Trans-Mexican Volcanic Belt
Herpetozoa, 2019Co-Authors: Octavio Monroy-vilchis, Rosa-laura Heredia-bobadilla, Martha M. Zarco-gonzález, Víctor Ávila-akerberg, Armando SunnyAbstract:The most important factor leading to amphibian population declines and extinctions is habitat degradation and destruction. To help prevent further extinctions, studies are needed to make appropriate conservation decisions in small and fragmented populations. The goal of this study was to provide data from the population genetics of two micro-endemic Mole Salamanders from the Trans-Mexican Volcanic Belt. Nine microsatellite markers were used to study the population genetics of 152 individuals from two Ambystoma species. We sampled 38 individuals in two localities for A. altamirani and A. rivualre. We found medium to high levels of genetic diversity expressed as heterozygosity in the populations. However, all the populations presented few alleles per locus and genotypes. We found strong genetic structure between populations for each species. Effective population size was small but similar to that of the studies from other Mole Salamanders with restricted distributions or with recently fragmented habitats. Despite the medium to high levels of genetic diversity expressed as heterozygosity, we found few alleles, evidence of a genetic bottleneck and that the effective population size is small in all populations. Therefore, this study is important to propose better management plans and conservation efforts for these species.
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Genetic diversity and demography of the critically endangered Roberts’ false brook Salamander (Pseudoeurycea robertsi) in Central Mexico
Genetica, 2019Co-Authors: Armando Sunny, Octavio Monroy-vilchis, Luis Duarte-dejesus, Arlene Aguilera-hernández, Fabiola Ramírez-corona, Marco Suárez-atilano, Ruth Percino-daniel, Javier Manjarrez, Andrea González-fernándezAbstract:Land use changes are threatening the maintenance of biodiversity. Genetic diversity is one of the main indicators of biological diversity and is highly important as it shapes the capability of populations to respond to environmental changes. We studied eleven populations of Pseudoeurycea robertsi , a micro-endemic and critically endangered species from the Nevado de Toluca Volcano, a mountain that is part of the Trans-Mexican Volcanic Belt, Mexico. We sequenced the mitochondrial cytochrome b gene from 71 individuals and genotyped 9 microsatellites from 150 individuals. Our results based on the cytochrome b showed two divergent lineages, with moderate levels of genetic diversity and a recently historical demographic expansion. Microsatellite-based results indicated low levels of heterozygosity for all populations and few alleles per locus, as compared with other Mole Salamander species. We identified two genetically differentiated subpopulations with a significant level of genetic structure. These results provide fundamental data for the development of management plans and conservation efforts for this critically endangered species.
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Genetic variability and structure of an isolated population of Ambystoma altamirani, a Mole Salamander that lives in the mountains of one of the largest urban areas in the world
Journal of Genetics, 2017Co-Authors: Rosa-laura Heredia-bobadilla, Octavio Monroy-vilchis, Martha M. Zarco-gonzález, Daniel Martínez-gómez, Germán David Mendoza-martínez, Armando SunnyAbstract:Amphibians are globally threatened by habitat loss and fragmentation; species within the order Ambystoma are not the exception, as there are 18 species of Mole Salamanders in México, of which 16 are endemic and all species are under some national or international status of protection. The Mole Salamander, Ambystoma altamirani is a microendemic species, which is distributed in central México, within the trans-Mexican volcanic belt, and is one of the most threatened species due to habitat destruction and the introduction of exotic species. Nine microsatellite markers were used to determine the genetic structure, genetic variability, effective population size, presence of bottlenecks and inbreeding coefficient of one population of A. altamirani to generate information which might help to protect and conserve this threatened species. We found two genetic subpopulations with significant level of genetic structure ( $$F_{\mathrm{ST}}= 0.005$$ F ST = 0.005 ) and high levels of genetic variability ( $$H_{\mathrm{o}}= 0.883$$ H o = 0.883 ; $$H_{\mathrm{e}}= 0.621$$ H e = 0.621 ); we also found a small population size ( $$N_{\mathrm{e}} = 8.8$$ N e = 8.8 ), the presence of historical ( $$M =$$ M = 0.486) and recent bottlenecks under IAM and TPM models, with a low, but significant coefficient of inbreeding ( $$F_{\mathrm{IS}} = -$$ F IS = - 0.451). This information will help us to raise conservation strategies of this microendemic Mole Salamander species.
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Genetic structure and diversity in an isolated population of an endemic Mole Salamander (Ambystoma rivulare Taylor, 1940) of central Mexico
Genetica, 2016Co-Authors: Rosa-laura Heredia-bobadilla, Octavio Monroy-vilchis, Martha M. Zarco-gonzález, Daniel Martínez-gómez, Germán David Mendoza-martínez, Armando SunnyAbstract:Human activities are affecting the distribution of species worldwide by causing fragmentation and isolation of populations. Isolation and fragmentation lead to populations with lower genetic variability and an increased chance of inbreeding and genetic drift, which results in a loss of biological fitness over time. Studies of the genetic structure of small and isolated populations are critically important for management and conservation decisions. Ambystoma rivulare is a micro-endemic Mexican Mole Salamander from central Mexico. It is found in the most ecologically disturbed region in Mexico, the Trans-Mexican Volcanic Belt. The goal of this study of the population genetics of the micro-endemic Mole Salamander was to provide information to be used as a basis for future research and conservation planning of this species and other species of the Ambystoma genus in Mexico. The structural analysis found two subpopulations, one for each river sampled, with no signs of admixture and very high levels of genetic differentiation. Medium to high levels of heterozygosity and few alleles and genotypes were observed. Evidence of an ancestral genetic bottleneck, low values of effective population size, small inbreeding coefficients, and low gene flow were also found.
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Microhabitat types promote the genetic structure of a micro-endemic and critically endangered Mole Salamander (Ambystoma leorae) of Central Mexico.
PloS one, 2014Co-Authors: Armando Sunny, Octavio Monroy-vilchis, Carlos Reyna-valencia, Martha M. Zarco-gonzálezAbstract:The reduced immigration and emigration rates resulting from the lack of landscape connectivity of patches and the hospitality of the intervening matrix could favor the loss of alleles through genetic drift and an increased chance of inbreeding. In order for isolated populations to maintain sufficient levels of genetic diversity and adapt to environmental changes, one important conservation goal must be to preserve or reestablish connectivity among patches in a fragmented landscape. We studied the last known population of Ambystoma leorae, an endemic and critically threatened species. The aims of this study were: (1) to assess the demographic parameters of A. leorae and to distinguish and characterize the microhabitats in the river, (2) to determine the number of existing genetic groups or demes of A. leorae and to describe possible relationships between microhabitats types and demes, (3) to determine gene flow between demes, and (4) to search for geographic locations of genetic discontinuities that limit gene flow between demes. We found three types of microhabitats and three genetically differentiated subpopulations with a significant level of genetic structure. In addition, we found slight genetic barriers. Our results suggest that Mole Salamander’s species are very sensitive to microhabitat features and relatively narrow obstacles in their path. The estimates of bidirectional gene flow are consistent with the pattern of a stepping stone model between demes, where migration occurs between adjacent demes, but there is low gene flow between distant demes. We can also conclude that there is a positive correlation between microhabitats and genetic structure in this population.