Publications by authors named "Elizabeth G Mandeville"

5 Publications

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Investigating the morphological and genetic divergence of arctic char ( populations in lakes of arctic Alaska.

Ecol Evol 2021 Apr 5;11(7):3040-3057. Epub 2021 Mar 5.

Department of Watershed Sciences and the Ecology Center Utah State University Logan UT USA.

Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char ( sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length-frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present-day char populations. Although some lakes exhibit bimodal size distributions, using model-based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food-limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.
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http://dx.doi.org/10.1002/ece3.7211DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8019052PMC
April 2021

Model-based genotype and ancestry estimation for potential hybrids with mixed-ploidy.

Mol Ecol Resour 2021 Jul 9;21(5):1434-1451. Epub 2021 Feb 9.

Department of Botany, University of Wyoming, Laramie, WY, USA.

Non-random mating among individuals can lead to spatial clustering of genetically similar individuals and population stratification. This deviation from panmixia is commonly observed in natural populations. Consequently, individuals can have parentage in single populations or involving hybridization between differentiated populations. Accounting for this mixture and structure is important when mapping the genetics of traits and learning about the formative evolutionary processes that shape genetic variation among individuals and populations. Stratified genetic relatedness among individuals is commonly quantified using estimates of ancestry that are derived from a statistical model. Development of these models for polyploid and mixed-ploidy individuals and populations has lagged behind those for diploids. Here, we extend and test a hierarchical Bayesian model, called entropy, which can use low-depth sequence data to estimate genotype and ancestry parameters in autopolyploid and mixed-ploidy individuals (including sex chromosomes and autosomes within individuals). Our analysis of simulated data illustrated the trade-off between sequencing depth and genome coverage and found lower error associated with low-depth sequencing across a larger fraction of the genome than with high-depth sequencing across a smaller fraction of the genome. The model has high accuracy and sensitivity as verified with simulated data and through analysis of admixture among populations of diploid and tetraploid Arabidopsis arenosa.
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http://dx.doi.org/10.1111/1755-0998.13330DOI Listing
July 2021

Variable hybridization outcomes in trout are predicted by historical fish stocking and environmental context.

Mol Ecol 2019 08 11;28(16):3738-3755. Epub 2019 Aug 11.

Department of Botany, University of Wyoming, Laramie, WY, USA.

Hybridization can profoundly affect the genomic composition and phenotypes of closely related species, and provides an opportunity to identify mechanisms that maintain reproductive isolation between species. Recent evidence suggests that hybridization outcomes within a species pair can vary across locations. However, we still do not know how variable outcomes of hybridization are across geographic replicates, and what mechanisms drive that variation. In this study, we described hybridization outcomes across 27 locations in the North Fork Shoshone River basin (Wyoming, USA) where native Yellowstone cutthroat trout and introduced rainbow trout co-occur. We used genomic data and hierarchical Bayesian models to precisely identify ancestry of hybrid individuals. Hybridization outcomes varied across locations. In some locations, only rainbow trout and advanced backcrossed hybrids towards rainbow trout were present, while trout in other locations had a broader range of ancestry, including both parental species and first-generation hybrids. Later-generation intermediate hybrids were rare relative to backcrossed hybrids and rainbow trout individuals. Using an individual-based simulation, we found that outcomes of hybridization in the North Fork Shoshone River basin deviate substantially from what we would expect under null expectations of random mating and no selection against hybrids. Since this deviation implies that some mechanisms of reproductive isolation function to maintain parental taxa and a diversity of hybrid types, we then modelled hybridization outcomes as a function of environmental variables and stocking history that are likely to affect prezygotic barriers to hybridization. Variables associated with history of fish stocking were the strongest predictors of hybridization outcomes, followed by environmental variables that might affect overlap in spawning time and location.
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http://dx.doi.org/10.1111/mec.15175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6775767PMC
August 2019

Inconsistent reproductive isolation revealed by interactions between fish species.

Evol Lett 2017 Nov 27;1(5):255-268. Epub 2017 Oct 27.

Department of Botany and Program in Ecology University of Wyoming Laramie Wyoming 82071.

Interactions between species are central to evolution and ecology, but we do not know enough about how outcomes of interactions between species vary across geographic locations, in heterogeneous environments, or over time. Ecological dimensions of interactions between species are known to vary, but evolutionary interactions such as the establishment and maintenance of reproductive isolation are often assumed to be consistent across instances of an interaction between species. Hybridization among fish species occurs over a large and heterogeneous geographic area and across taxa with distinct evolutionary histories, which allows us to assess consistency in species interactions. We analyzed hybridization among six species across the Upper Colorado River basin (US mountain west) and found extreme variation in hybridization across locations. Different hybrid crosses were present in different locations, despite similar species assemblages. Within hybrid crosses, hybridization varied from only first generation hybrids to extensive hybridization with backcrossing. Variation in hybridization outcomes might result from uneven fitness of hybrids across locations, polymorphism in genetic incompatibilities, chance, unidentified historical contingencies, or some combination thereof. Our results suggest caution in assuming that one or a few instances of hybridization represent all interactions between the focal species, as species interactions vary substantially across locations.
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http://dx.doi.org/10.1002/evl3.29DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6121845PMC
November 2017

Highly variable reproductive isolation among pairs of Catostomus species.

Mol Ecol 2015 Apr 23;24(8):1856-72. Epub 2015 Mar 23.

Department of Botany, University of Wyoming, Laramie, WY, 82071, USA; Program in Ecology, University of Wyoming, Laramie, WY, 82071, USA.

Hybridization between diverged taxa tests the strength of reproductive isolation and can therefore reveal mechanisms of reproductive isolation. However, it remains unclear how consistent reproductive isolation is across species' ranges and to what extent reproductive isolation might remain polymorphic as species diverge. To address these questions, we compared outcomes of hybridization across species pairs of Catostomus fishes in three rivers in the Upper Colorado River basin, where an introduced species, C. commersoni, hybridizes with at least two native species, C. discobolus and C. latipinnis. We observed substantial heterogeneity in outcomes of hybridization, both between species pairs and across geographically separate rivers within each species pair. We also observed hybridization of additional related species with our focal species, suggesting that reproductive isolation in this group involves interactions of multiple evolutionary and ecological factors. These findings suggest that a better understanding of the determinants of variation in reproductive isolation is needed and that studies of reproductive isolation in hybrids should consider how the dynamics and mechanisms of reproductive isolation vary over ecological space and over evolutionary time. Our results also have implications for the conservation and management of native catostomids in the Colorado River basin. Heterogeneity in outcomes of hybridization suggests that the threat posed by hybridization and genetic introgression to the persistence of native species probably varies with extent of reproductive isolation, both across rivers and across species pairs.
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http://dx.doi.org/10.1111/mec.13118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4390503PMC
April 2015