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Author: Joseph E. Bartoszek
Publisher:
ISBN:
Category : Ambystomatidae
Languages : en
Pages : 173
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Book Description
It is generally recognized that amphibian populations declining across the globe. Habitat loss is the primary cause of decline. The salamander family Ambystomatidae has experienced significantly more rapid decline than the average for amphibians. Coefficients of Conservatism (CoC) have been developed for amphibians in Ohio. These are based primarily on habitat requirements with high CoCs for amphibians with stringent habitat requirements (e.g. vernal pools associated with large, intact, undisturbed forest), and low CoCs for amphibians with less stringent habitat requirements. Genetic diversity in five species and one hybrid complex of ambystomatid salamander in southwest Ohio were examined and compared to their respective CoC. Less gene flow across inhospitable habitat and consequently lower genetic diversity in that species would be expected compared with a species with less restrictive habitat requirements, i.e. a lower CoC. Microsatellites were used to determine conformation to Hardy Weinberg Equilibrium expectations, allelic and genotypic differences between populations, and inbreeding coefficients Fis and Fst. Genetic differences between woodlots and between ponds within a woodlot were examined. It was found that, for different species in the same habitat, species with higher CoCs have lower genetic diversity than species with lower CoCs. It was also found that habitat quality influences genetic diversity in all species. In some habitats, the genetic diversity of all species in that habitat will be lower than that of the same species in a more suitable habitat. In some cases presence of the hybrid complex (kleptogens) appears to have negatively impacted species that act as a sperm donor to the hybrid complex. In some species (e.g. smallmouth salamanders) genetic structure can be seen in different ponds within a woodlot. In other species (e.g. tiger salamanders) no such structure appears. It was also found that a railroad track acts as a barrier to marbled salamanders creating two genetically distinct populations. It was found that maternal ancestor of the kleptogens, A. barbouri, also acts as a sperm donor but does not replace the A. laterale genome in the nucleus. In addition to species specific differences in genetic diversity, habitat quality, and presence of kleptogens also influence genetic diversity in ambystomatid salamanders.
Author: Joseph E. Bartoszek
Publisher:
ISBN:
Category : Ambystomatidae
Languages : en
Pages : 173
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Book Description
It is generally recognized that amphibian populations declining across the globe. Habitat loss is the primary cause of decline. The salamander family Ambystomatidae has experienced significantly more rapid decline than the average for amphibians. Coefficients of Conservatism (CoC) have been developed for amphibians in Ohio. These are based primarily on habitat requirements with high CoCs for amphibians with stringent habitat requirements (e.g. vernal pools associated with large, intact, undisturbed forest), and low CoCs for amphibians with less stringent habitat requirements. Genetic diversity in five species and one hybrid complex of ambystomatid salamander in southwest Ohio were examined and compared to their respective CoC. Less gene flow across inhospitable habitat and consequently lower genetic diversity in that species would be expected compared with a species with less restrictive habitat requirements, i.e. a lower CoC. Microsatellites were used to determine conformation to Hardy Weinberg Equilibrium expectations, allelic and genotypic differences between populations, and inbreeding coefficients Fis and Fst. Genetic differences between woodlots and between ponds within a woodlot were examined. It was found that, for different species in the same habitat, species with higher CoCs have lower genetic diversity than species with lower CoCs. It was also found that habitat quality influences genetic diversity in all species. In some habitats, the genetic diversity of all species in that habitat will be lower than that of the same species in a more suitable habitat. In some cases presence of the hybrid complex (kleptogens) appears to have negatively impacted species that act as a sperm donor to the hybrid complex. In some species (e.g. smallmouth salamanders) genetic structure can be seen in different ponds within a woodlot. In other species (e.g. tiger salamanders) no such structure appears. It was also found that a railroad track acts as a barrier to marbled salamanders creating two genetically distinct populations. It was found that maternal ancestor of the kleptogens, A. barbouri, also acts as a sperm donor but does not replace the A. laterale genome in the nucleus. In addition to species specific differences in genetic diversity, habitat quality, and presence of kleptogens also influence genetic diversity in ambystomatid salamanders.
Author: Elizabeth Anne Rhoads
Publisher:
ISBN:
Category : Ambystomatidae
Languages : en
Pages : 102
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Book Description
Habitat loss is the leading cause of species declines and extinctions worldwide. Fragmentation of original habitat into patches often accompanies habitat loss and spatially separates breeding populations across a landscape. Habitat fragmentation poses additional challenges for species by degrading habitat quality, altering population abundance and density, and decreasing gene flow among breeding populations in separate patches. Wetland loss and deforestation in western Ohio has fragmented both breeding and terrestrial habitat for woodland amphibians, where agriculture is now the dominant landuse. This project utilized genetic markers to study the effect of habitat fragmentation on the population structure of a woodland amphibian, the small-mouthed salamander (Ambystoma texanum), in Hardin County, Ohio. This species breeds in vernal pools within forest patches, and has low vagility. It was hypothesized that salamanders were not migrating between forest patches; and that populations in different forest patches would show genetic differentiation and small populations would have decreased genetic diversity. A method was developed to screen for unisexual Ambystoma salamanders, which also reproduce in vernal pools in the study area and whose larvae are difficult to distinguish from A. texanum larvae. For the population genetic analysis, a total of 160 A. texanum from eight breeding populations in five forest patches were genotyped for eight highly polymorphic microsatellite loci. The results indicate that all sampled populations have within-population structure, with the two most isolated populations having the highest inbreeding coefficients. Estimates of historical migration rates reveal that gene flow occurred in the past among sites that today show genetic differentiation. Overall our results suggest that forest fragmentation and wetland loss have reduced the connectivity of breeding populations, which supports numerous studies that implicate landscape change as the main threat to species decline.
Author: Stephen Spear
Publisher:
ISBN:
Category : Microsatellites (Genetics)
Languages : en
Pages : 12
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Book Description
The field of landscape genetics has great potential to identify habitat features that influence population genetic structure. To identify landscape correlates of genetic differentiation in a quantitative fashion, we developed a novel approach using geographical information systems analysis. We present data on blotched tiger salamanders (Ambystoma tigrinum melanostictum) from 10 sites across the northern range of Yellowstone National Park in Montana and Wyoming, USA. We used eight microsatellite loci to analyse population genetic structure. We tested whether landscape variables, including topographical distance, elevation, wetland likelihood, cover type and number of river and stream crossings, were correlated with genetic subdivision (FST ). We then compared five hypothetical dispersal routes with a straight-line distance model using two approaches: (i) partial Mantel tests using Akaike?s information criterion scores to evaluate model robustness and (ii) the BIOENV procedure, which uses a Spearman rank correlation to determine the combination of environmental variables that best fits the genetic data. Overall, gene flow appears highly restricted among sites, with a global FST of 0.24. While there is a significant isolation-bydistance pattern, incorporating landscape variables substantially improved the fit of the model (from an r2 of 0.3 to 0.8) explaining genetic differentiation. It appears that gene flow follows a straight-line topographic route, with river crossings and open shrub habitat correlated with lower FST and thus, decreased differentiation, while distance and elevation difference appear to increase differentiation. This study demonstrates a general approach that can be used to determine the influence of landscape variables on population genetic structure.
Author: Bradley J. Cosentino
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Metapopulation biology has been integral for understanding the impact of spatial habitat structure on ecological and evolutionary processes. In fragmented landscapes, theory predicts that species occupancy and turnover dynamics depend on habitat area and isolation, and isolation has historically been an important predictor of gene flow. However, metapopulation theory is neutral with respect to the effects of habitat heterogeneity on population processes. Landscape ecology approaches have begun to account for effects of habitat quality and matrix structure on occupancy and gene flow, but few empirical studies have integrated the area-isolation and habitat paradigms to understand metapopulation dynamics and genetic structure in the same system. Here, I employ both approaches to understand the spatial population dynamics and genetic structure of tiger salamanders (Ambystoma tigrinum tigrinum) in an agricultural landscape in Illinois. First, I assessed the degree to which matrix heterogeneity influences A. tigrinum movement behavior. Using a field experiment, I showed that a physiological constraint, desiccation risk, varied significantly among matrix habitats (corn, soybean, forest, prairie). Water loss was greater in corn and prairie than in forest and soybean, indicating that dispersal costs can vary among agricultural crops. To assess whether movement decisions were influenced by desiccation risk, I tracked the movements of individuals released on habitat boundaries for two treatment combinations: soybean-corn, soybean-prairie. I observed that movements were oriented towards soybean in both cases, suggesting that variation in desiccation risk among matrix habitats influenced salamander movement decisions. Next, I examined the effects of area, isolation, and habitat heterogeneity on metapopulation dynamics of A. tigrinum. Emphasis was placed on understanding the role of connectivity in moderating interactions between A. tigrinum and predatory fish. Occupancy and turnover of A. tigrinum were documented in 90 wetlands for three years. Since desiccation risk influenced A. tigrinum movements, I tested whether a connectivity metric that accounted for desiccation was a better predictor of occupancy and turnover than metrics based on Euclidean distance or expert opinion. Occupancy and colonization probabilities were related positively to connectivity and negatively to fish presence. Extinction probability was related positively to fish presence, but extinction risk was low in connected networks, suggesting a rescue effect. A desiccation-informed connectivity metric was a better predictor of colonization probability than alternative metrics, whereas a Euclidean model was the best predicator of occupancy and extinction probabilities. The results indicated that the effect of desiccation risk on individual movement can scale up to influence metapopulation processes, and that the effects of predatory fish on metapopulation dynamics depended on spatial connectivity. Finally, I evaluated whether ecological factors underlying occupancy and turnover were also important predictors of metapopulation genetic structure. Newly colonized populations were more genetically differentiated than established populations, indicating that founder effects influenced genetic structure. However, the degree of genetic differentiation varied spatially. Genetic differentiation was related negatively to both wetland area and spatial connectivity. Differentiation was not strongly related to habitat quality, suggesting that metapopulation factors were more effective at reflecting the historical strength of genetic drift and gene flow than current habitat suitability.
Author: William Earl Peterman
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 95
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Inferring process from pattern can be a challenging undertaking when dealing with ecological complexity. The distribution and abundance of organisms on the landscape is often interpreted through the lens of competition, movement, or physiology, as well as interactions with the abiotic environment. Further, movement, distribution, and abundance often coincide with favorable abiotic environments such as temperature, moisture, or nutrients. At its core, landscape genetics seeks to identify the spatial processes shaping the observed patterns of genetic diversity across the landscape, but most landscape genetic studies are predominantly exploratory and lack well-established hypotheses. To increase understanding of process-driven patterns in landscape genetics, I studied the western slimy salamander (Plethodon albagula) in east-central Missouri with three specific questions: (1) Where are salamanders on the landscape, and what environmental factors influence local abundance? (2) Is there a physiological constraint underlying the observed patterns of distribution and abundance? (3) How is spatial genetic structure shaped by abundance and physiology across the landscape? I utilized a combination of abundance modeling, spatial quantification of water loss using plaster of Paris models, and landscape genetics analyses to assess the factors contributing to genetic differentiation across a 1300 ha landscape. Plethodontid salamanders are highly sensitive to water loss, in part due to their lack of lungs and cutaneous respiration. I found that abundance of salamanders was best predicted by canopy cover, topographic position (ridge, slope, ravine), and the interaction between wetness and solar exposure. The spatial relationships of these factors are such that abundance is predicted to be highest in forested ravines with lower solar exposure. Plaster models deployed across the landscape served as surrogates for live salamanders to quantify rates of water loss. I found that rates of water loss across the landscape were inversely related to predicted abundance, suggesting that water loss is likely a physiologically-limiting process underlying the distribution of salamanders. Finally, I determined that genetic distances were significantly correlated with ecological surfaces, and that the independent landscape features underlying these processes were poor predictors of genetic differentiation. My results highlight the importance of understanding basic ecological and physiological factors as mechanisms for interpreting spatial genetic patterns.
Author: Robert D. Denton
Publisher:
ISBN:
Category : Biology
Languages : en
Pages :
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Every year, there is at least one widespread news story documenting a "virgin birth" in a variety of animals as diverse as snakes and sharks. These events capture our attention because they represent departures from an assumed necessity of vertebrate life: having sex. Yet, vertebrates do not always reproduce via sex, and biologists have long studied the evolutionary costs and benefits of this type of reproduction. One of the main costs of sex are males, who cannot directly generate offspring and use up resources from reproductive females that cannot be put towards additional offspring. Eastern North America is home to one of the strangest vertebrates that lack males and appear to be sexual and asexual at the same time: an all-female group of salamanders that appear to “steal” sperm from males of other species. These all-female salamanders can potentially retain the advantage of gaining new genetic diversity from other species without males of their own. However, the extent and flexibility of this mating systems is still not understood, and the factors that promote the coexistence of all-female salamander lineages and the sexual species from which they use reproductive material are mysterious. I have investigated three primary questions concerning these unusual animals. First, how do we identify an all-female salamander in Ohio? Because of their cryptic morphology compared to similar sexual species, all-female Ambystoma salamanders are only reliably identified by sequencing their mitochondrial DNA, which is independently transferred maternally. However, mitochondrial sequences that closely resembled those of all-female salamanders were previously found in salamander individuals across Ohio that were identified morphologically as either the smallmouthed or streamside salamander. I gathered microsatellite data from these potentially misidentified animals and evaluated three hypotheses for why the mitochondrial data does not match the nuclear DNA or morphological species identity. The best supported hypothesis was one of mitochondrial introgression, where the mitochondrial haplotypes of one species (streamside salamanders) were introgressed into populations of another species (smallmouth salamanders). This chapter describes the evolutionary basis for the discordance between mitochondrial and nuclear DNA markers and provides necessary diagnostic information to correctly identify all-female salamander lineages in Ohio. Second, can differences in dispersal between breeding environments dictate the coexistence between all-female salamanders and other salamander species, preventing mutual extinction? I inferred salamander movements across a fragmented agricultural landscape in Ohio with genetic data and treadmill endurance trials, and I found that sexual species traveled significantly greater distances between breeding sites and fatigue much more slowly than unisexuals, contrary to a hypothesis that would explain the ecological coexistence between these groups. Third, what environmental factors determine the coexistence of all-female salamanders and their sexual relatives at broad scales? I gathered rangewide occurrence data for blue-spotted, Jefferson's salamanders, and all-female salamanders that vary by the number of nuclear genomes possessed from either sexual species. By comparing the niche overlap from ecological niche models representing all-female salamander groups and each sexual species, I found that neither the total number of genomes or the composition of all-female salamander genomes explained the amount of niche overlap. Instead, niche overlap was significantly greater than expected for all comparisons between sexual species and the all-female lineage. I additionally used joint species modeling techniques to suggest that species interactions, in this case the all-female salamanders' reproductive requirement for sperm, are the most powerful predictor of ecological niche in all-female salamanders and limit their ability to differentiate from their sexual relatives. Taken together, these chapters have expanded our understanding of how all-female salamanders have evolved to navigate the tradeoffs of intermediacy between sexual and asexual reproduction while providing new avenues of research for the future, including physiological limitations in members of the all-female lineage and molecular discordance between their separate mitochondrial and nuclear genomes.
Author: Stephen Randal Voss
Publisher:
ISBN:
Category :
Languages : en
Pages : 248
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Author: Miranda Gaupp
Publisher:
ISBN:
Category : Ambystoma
Languages : en
Pages : 0
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Author's abstract: The Reticulated flatwoods salamander (Ambystoma bishopi) is a federally endangered amphibian endemic to the longleaf-pine ecosystem of the southeastern U.S. This study used analyses of single-nucleotide polymorphism (SNP) data, collected from 2,255 unique individuals across 5 breeding seasons, spread across the known extant range of A. bishopi, to characterize the genetic diversity and demographics of populations, genetic relationships among populations, and patterns and spatial extents of gene flow, and to evaluate potential effects of management on A. bishopi’s resiliency. Population structure was strongly hierarchical, with individual breeding ponds (n = 38) acting as semi-connected subpopulations within five regional metapopulations (Mayhaw in Georgia; Oglesby, Eastbay, Garcon, and Escribano in Florida). Likewise, gene flow among populations was scale-dependent: negligible genetic differentiation, indicative of high gene flow, was observed only between pairs of ponds separated by 0.5 km, whereas between 0.5 and 5 km I observed steep genetic isolation by distance, and beyond 5 km genetic differentiation was generally high and only weakly related to distance. Across several breeding seasons, the effective number of breeders (Nb) per pond per year averaged 26 individuals (range 4 to 104). Larger-area, slower-drying ponds located closer to other occupied ponds exhibited larger Nb and greater genetic diversity. Based on genetically-reconstructed pedigrees, the ongoing headstarting program at Escribano successfully captured 97.9% of the estimated total number of alleles, but only 63% of the total number families, in each cohort. Based on these results, I recommend the following: 1) Given its genetic distinctiveness, Georgia populations merit elevated priority for protection and restoration. 2) Resiliency and redundancy (a la the species’ recovery plan) should be assessed at the spatial grain of individual breeding ponds. 3) Attempts to restore habitat connectivity should consider dispersal over distances 500 m to be relatively unlikely. 4) Finally, to the extent that headstarted individuals are used to augment existing or introduce new populations, managers should consider the potential risks of founder effects, and reduce these risks by creating genetically and demographically diverse headstart samples, for example by maximizing the diversity of egg/larva collections over time and space within ponds.
Author: Jennifer Lyn Purrenhage
Publisher:
ISBN:
Category : Spotted salamander
Languages : en
Pages : 60
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Author: C. Kenneth Dodd
Publisher: Oxford University Press
ISBN: 0199541191
Category : Nature
Languages : en
Pages : 585
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Describes the latest methodologies used to study the ecology of amphibians throughout the world. Each of the 27 chapters explains a research approach or technique, with emphasis on careful planning and the potential biases of techniques. Statistical modelling, landscape ecology, and disease are covered for the first time in a techniques handbook.
