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opencc-zeroAug 2020View details →

Data from: Genome-wide diversity and habitat underlie fine-scale phenotypic differentiation in the rainbow darter (Etheostoma caeruleum)

Adaptation to environmental change requires that populations harbor the necessary genetic variation to respond to selection. However, dispersal-limited species with fragmented populations and reduced genetic diversity may lack this variation and are at an increased risk of local extinction. In freshwater fish species, environmental change in the form of increased stream temperatures places many cold-water species at-risk. We present a study of rainbow darters (Etheostoma caeruleum) in which we evaluated the importance of genetic variation on adaptive potential and determined responses to extreme thermal stress. We compared fine-scale patterns of morphological and thermal tolerance differentiation across eight sites, including a unique lake habitat. We also inferred contemporary population structure using genomic data and characterized the relationship between individual genetic diversity and stress tolerance. We found site-specific variation in thermal tolerance that generally matched local conditions and morphological differences associated with lake-stream divergence. We detected patterns of population structure on a highly local spatial scale that could not be explained by isolation by distance or stream connectivity. Finally, we showed that individual thermal tolerance was positively correlated with genetic variation, suggesting that sites with increased genetic diversity may be better at tolerating novel stress. Our results highlight the importance of considering intraspecific variation in understanding population vulnerability and stress response.

opencc-zeroJan 2021View details →

Reinforcement in the banded darter Etheostoma zonale: the effect of sex and sympatry on preferences

Reinforcement occurs when selection against hybrid offspring strengthens behavioral isolation between parental species and may be an important factor in speciation. Theoretical models and experimental evidence indicate that both female and male preferences can be strengthened upon secondary contact via reinforcement. However, the question remains whether this process is more likely to affect the preferences of one sex or the other. Males of polygynous species are often predicted to exhibit weaker preferences than females, potentially limiting the ability for reinforcement to shape male preferences. Yet, in darters (Percidae: Etheostoma), male preference for conspecific mates appears to arise before female preferences during the early stages of allopatric speciation, and research suggests that male, but not female, preferences become reinforced upon secondary contact. In the current study, we aimed to determine whether the geographically widespread darter species Etheostoma zonale exhibits a signature of reinforcement, by comparing the strength of preference for conspecific mates between populations that are sympatric and allopatric with respect to a close congener, E. barrenense. We examined the strength of preference for conspecifics for males and females separately to determine if the preferences of one or both sexes have been strengthened by reinforcement. Our results show that both sexes of E. zonale from sympatric populations exhibit stronger conspecific preferences than E. zonale from allopatric populations, but that female preferences appear to be more strongly reinforced than male preferences. Results therefore suggest that reinforcement of female preferences may promote behavioral isolation upon secondary contact, even in a genus that is characterized by pervasive male mate choice.

opencc-zeroSep 2019View details →

Data from: Genetic structure and diversity of the blueface darter Etheostoma cyanoprosopum, a microendemic freshwater fish in the southeastern United States

Darters represent one of the most diverse groups of freshwater fishes in North America, but approximately 33% of the 215 recognized species are considered imperiled on the IUCN Red List. Discovery and description of new darter species continues at a relatively rapid pace, with many exhibiting microendemic geographic distributions and little baseline data for conservation decisions. The Blueface Darter Etheostoma cyanoprosopum is a newly described species that occupies < 20 km of stream reaches in the Bear Creek system of the Tennessee River drainage and the Hubbard Creek system of the Black Warrior River drainage in the Mobile Basin (Alabama, USA). In addition to restricted distribution, the species is threatened by habitat degradation and several natural and man-made barriers that putatively fragment connectivity among populations. This study used microsatellite and mitochondrial (mt) DNA data with comparisons to the relatively broadly distributed sister species (Bandfin Darter E. zonistium) to evaluate multiple objectives about genetic connectivity and diversity among Blueface Darter populations. Analysis of mtDNA data indicated a lack of historical structuring across the Tennessee-Black Warrior river drainage divide and within the Bear Creek system. However, microsatellite-based Bayesian cluster analyses and F-statistics suggested contemporary isolation across the drainage divide and evidence for reservoir-induced fragmentation within the Bear Creek system. Compared to the sister Bandfin Darter, Blueface Darter populations exhibited reduced levels of genetic diversity, rendering them more susceptible to local extirpation and reduced fitness. Continued monitoring and quantitative ecological studies are recommended to understand population-specific measures of occurrence and abundance.

opencc-zeroDec 2016View details →

Data from: Genetic diversity and divergence in the fountain darter (Etheostoma fonticola): implications for conservation of an endangered species

The endangered fountain darter Etheostoma fonticola is found only in the Comal and San Marcos rivers in the Guadalupe River basin in central Texas, USA. Comal River fountain darters were believed to be extir- pated following a severe drought in the 1950s and were reintroduced in the early 1970s using 457 darters from the San Marcos River. In this study we used 23 microsatellite loci to describe and evaluate the genetic diversity, population structure and effective population size (Ne) of fountain darters. We also evaluated the genetic effect of the Comal River reintroduction and the influence of low-head dams (dams) on dispersal in both rivers. Bayesian analysis of individual genotypes and Analysis of Molecular Variation supported two distinct populations concordant with the two rivers. Estimates of Ne were much smaller (<10 %) than census size (Nc) in both rivers but did not indicate the populations are at risk of an immediate and rapid loss of genetic diversity. Coalescent-based estimates of the genetically effective number of founders (Nf) for the Comal River averaged about 49 darters and, together with the indices of genetic diversity and the bottleneck test (heterozygosity excess) results, were consistent with a founder event following the reintroduction in the Comal River. Finally, our results regarding the influence of dams on fountain darter dispersal were equivocal and did not support a conclusion. We recommend this issue be examined further as part of the fountain darter recovery program.

opencc-zeroOct 2022View details →

Data from: Phylogeography, hybridization, and species discovery in the Etheostoma nigrum complex (Percidae: Etheostoma: Boleosoma)

The history of riverine fish diversification is largely a product of geographic isolation. Physical barriers that reduce or eliminate gene flow between populations facilitate divergence via genetic drift and natural selection, eventually leading to speciation. For freshwater organisms, diversification is often the product of drainage basin rearrangements. In young clades where the history of isolation is the most recent, evolutionary relationships can resemble a tangled web. One especially recalcitrant group of freshwater fishes is the Johnny Darter (Etheostoma nigrum) species complex, where traditional taxonomy and molecular phylogenetics indicate a history of gene flow and conflicting inferences of species diversity. Here we assemble a genomic dataset using double digest restriction site associated DNA (ddRAD) sequencing and use phylogenomic and population genetic approaches to investigate the evolutionary history of the complex of species that includes E. nigrum, E. olmstedi, E. perlongum, and E. susanae. We reveal and validate several evolutionary lineages that we delimit as species, highlighting the need for additional work to formally describe the diversity of the Etheostoma nigrum complex. Our analyses also identify gene flow among recently diverged lineages, including one instance involving E. susanae, a localized and endangered species. Phylogeographic structure within the Etheostoma nigrum species complex coincides with major geologic events, such as parallel divergence in river basins during Pliocene inundation of the Atlantic coastal plain and multiple northward post-glacial colonization routes tracking river basin rearrangements. Our study serves as a nuanced example of how low dispersal rates coupled with geographic isolation among disconnected river systems in eastern North America have produced one of the world's freshwater biodiversity hotspots.

opencc-zeroJan 2023View details →

Trans-specific polymorphism and the convergent evolution of supertypes in MHC class II genes in Darters (Etheostoma)

Major Histocompatibility Complex (MHC) genes are one of the most polymorphic gene groups known in vertebrates. MHC genes also exhibit allelic variants that are shared among taxa, referred to as trans-specific polymorphism (TSP). The role that selection plays in maintaining such high diversity within species, as well as TSP, is an ongoing discussion in biology. In this study we used deep-sequencing techniques to characterize MHC class IIb gene diversity in three sympatric species of darters. We found at least 5 copies of the MHC gene in darters, with 126 genetic variants encoding 122 unique amino acid sequences. We identified four supertypes based on the binding properties of proteins encoded by the sequences. Although each species had a unique pool of variants, many variants were shared between species pairs and across all three species. Phylogenetic analysis showed that the variants did not group together monophyletically based on species identity or on supertype. An expanded phylogenetic analysis showed that some darter alleles grouped together with alleles from other percid fishes. Our findings show that TSP occurs in darters, which suggests that balancing selection is acting at the genotype level. Supertypes, however, are most likely evolving convergently, as evidenced by the fact that alleles do not form monophyletic groups based on supertype. Our research demonstrates that selection may be acting differently on MHC genes at the genotype and supertype levels, selecting for the maintenance of high genotypic diversity while driving the convergent evolution of similar MHC phenotypes across different species.

opencc-zeroSep 2023View details →

Data from: Conservation genomics of the threatened Trispot Darter (Etheostoma trisella)

The southeastern United States is a hotspot of biodiversity, but aquatic habitats are fragmented by anthropogenic activities such as hydrologic alteration. Small-stream-inhabiting fish can suffer population declines, loss of genetic diversity, and migration impediment from riverine impoundment. The Trispot Darter (Etheostoma trisella) is a small, freshwater fish endemic to the southeastern United States. E. trisella was previously believed to be extinct and has now been listed as threatened under the U.S. Endangered Species Act, due to destruction of its limited habitat and a restricted range. We used mitochondrial DNA (NADH dehydrogenase subunit 2 gene), seven microsatellite loci, and 9732 single nucleotide polymorphisms (SNPs) to evaluate population structure and diversity in E. trisella. Mitochondrial data provided evidence of historical connectivity between populations, with haplotype sharing across populations and weak support for population structure. Microsatellite and SNP data, however, indicate that populations have more recently become isolated. Furthermore, we detect three distinct management units (i.e., genetic groups) which reflect isolated geographic localities (i.e., Little Canoe Creek, Ballplay Creek, and a system including the Conasauga and Coosawattee rivers). We also detected a recent bottleneck event in the Ballplay Creek population as well as a low effective population size. Tests of isolation by distance further suggest that populations are structured by riverine isolation rather than geographic distance. A better understanding about the distribution, abundance, and habitat occupancy of all E. trisella populations will be important for informing future decisions for conservation of the species.

publicOct 2021View details →

Reinforcement in the banded darter Etheostoma zonale: the effect of sex and sympatry on preferences

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publicSep 2020View details →

Data from: Genome-wide diversity and habitat underlie fine-scale phenotypic differentiation in the rainbow darter (Etheostoma caeruleum)

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publicSep 2019View details →

Data from: Genetic structure and diversity of the blueface darter Etheostoma cyanoprosopum, a microendemic freshwater fish in the southeastern United States

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publicOct 2021View details →

Data from: Genetic diversity and divergence in the fountain darter (Etheostoma fonticola): implications for conservation of an endangered species

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publicSep 2023View details →

Data from: Conservation genomics of the threatened Trispot Darter (Etheostoma trisella)

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publicOct 2022View details →

Data from: Phylogeography, hybridization, and species discovery in the Etheostoma nigrum complex (Percidae: Etheostoma: Boleosoma)

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publicJan 2023View details →

Trans-specific polymorphism and the convergent evolution of supertypes in MHC class II genes in Darters (Etheostoma)

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North Temperate Lakes site, station Allequash Lake, study of animal abundance of Etheostoma nigrum in units of numberPerEffort on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from North Temperate Lakes (NTL) contains animal abundance of Etheostoma nigrum measurements in numberPerEffort units and were aggregated to a yearly timescale.

North Temperate Lakes site, station Allequash Lake, study of animal abundance of Etheostoma exile in units of numberPerEffort on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from North Temperate Lakes (NTL) contains animal abundance of Etheostoma exile measurements in numberPerEffort units and were aggregated to a yearly timescale.

North Temperate Lakes site, station Allequash Lake, study of animal abundance of Etheostoma flabellare in units of numberPerEffort on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from North Temperate Lakes (NTL) contains animal abundance of Etheostoma flabellare measurements in numberPerEffort units and were aggregated to a yearly timescale.

North Temperate Lakes site, station Big Muskellunge Lake, study of animal abundance of Etheostoma in units of numberPerEffort on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from North Temperate Lakes (NTL) contains animal abundance of Etheostoma measurements in numberPerEffort units and were aggregated to a yearly timescale.