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opencc-zeroJan 2024View details →

A lack of genetic diversity and minimal adaptive evolutionary divergence in introduced Mysis shrimp after 50 years

The successes of introduced populations in novel habitats often provide powerful examples of evolution and adaptation. In the 1950's, opossum shrimp (Mysis diluviana) individuals from Clearwater Lake in Minnesota, USA were transported and introduced to Twin Lakes in Colorado, USA by fisheries managers to supplement food sources for trout. Shrimp were subsequently introduced from Twin Lakes into numerous lakes throughout Colorado. Because managers kept detailed records of the timing of the introductions, we had the opportunity to test for evolutionary divergence within a known time interval. Here, we used reduced representation genomic data to investigate patterns of genetic diversity and test for genetic divergence between populations and for evidence of adaptive evolution within the introduced populations in Colorado. We found overall very low levels of genetic diversity across all populations, with evidence for some genetic divergence between the Minnesota source population and the introduced populations in Colorado. There was also little differentiation among the Colorado populations, consistent with the known provenance of a single founding population, with the exception of the population from Gross Reservoir, Colorado. Demographic modeling suggests that the population in Gross Reservoir is of hybrid origin, with an earlier founding population from an unknown source being later supplemented from another population. Despite the overall low genetic diversity we observed, FST outlier and environmental association analyses identified multiple loci exhibiting signatures of selection and adaptive variation related to elevation and lake depth. The success of introduced species is thought to be limited by genetic variation, but our results imply that populations with limited genetic variation can become established in a wide range of novel environments.

FIGURE 1 in A new species of Knodus (Characiformes: Characidae), with deep genetic divergence, from the Mearim and Munim river basins, Northeastern Brazil, and evidence for hidden diversity in adjacent river basins

FIGURE 1 | Knodus guajajara, holotype, CICCAA 4883, 31.4 mm SL, Alto Alegre do Pindaré municipality, Igarapé Arapapá, Pindaré River drainage, Mearim River basin.

FIGURE 4 in A new species of Knodus (Characiformes: Characidae), with deep genetic divergence, from the Mearim and Munim river basins, Northeastern Brazil, and evidence for hidden diversity in adjacent river basins

FIGURE 4 | Knodus guajajara, CICCAA 4861, paratype, male, 31.9 mm SL Maranhão, Mearim River basin. A. Hooks on pelvic fin. B. Hooks on anal fin. (Photographed by F. P. Ottoni).

FIGURE 2 in A new species of Knodus (Characiformes: Characidae), with deep genetic divergence, from the Mearim and Munim river basins, Northeastern Brazil, and evidence for hidden diversity in adjacent river basins

FIGURE 2 | Knodus guajajara, paratypes. A. CICCAA 1518, 22.8 mm SL, Brazil, Maranhão, Alto Alegre do Pindaré municipality, igarapé Jenipapo, Pindaré River drainage, Mearim River basin. B. CICCAA 2696, 40.2 mm SL, Brazil, Maranhão, Chapadinha municipality, stream in riparian forest on the road BR–222, Munim River basin.

FIGURE 3 in A new species of Knodus (Characiformes: Characidae), with deep genetic divergence, from the Mearim and Munim river basins, Northeastern Brazil, and evidence for hidden diversity in adjacent river basins

FIGURE 3 | Knodus guajajara, CICCAA 4861, paratype, 31.9 mm SL, jaw suspensorium. A. Premaxillary. B. Maxilla. C. Dentary. Scale bar = 1 mm.

opencc-zeroJan 2023View details →

Whole genome demographic models indicate divergent effective population size histories shape contemporary genetic diversity gradients in a montane bumble bee

Understanding historical range shifts and population size variation provides important context for interpreting contemporary genetic diversity. Methods to predict changes in species distributions and model changes in effective population size (Ne) using whole genomes make it feasible to examine how temporal dynamics influence diversity across populations. We investigate Ne variation and climate-associated range shifts to examine the origins of a previously observed latitudinal heterozygosity gradient in the bumble bee Bombus vancouverensis Cresson (Hymenoptera: Apidae: Bombus Latreille) in western North America. We analyze whole genomes from a latitude-elevation cline using sequentially Markovian coalescent models of Ne through time to test whether relatively low diversity in southern high-elevation populations is a result of long-term differences in Ne. We use Maxent models of the species range over the last 130,000 years to evaluate range shifts and stability. Ne fluctuates with climate across populations, but more genetically diverse northern populations have maintained greater Ne over the late Pleistocene and experienced larger expansions with climatically favorable time periods. Northern populations also experienced larger bottlenecks during the last glacial period which matched the loss of range area near these sites, however, bottlenecks were not sufficient to erode diversity maintained during periods of large Ne. A genome sampled from an island population indicated a severe postglacial bottleneck, indicating that large recent post-glacial declines are detectable if they have occurred. Genetic diversity was not related to niche stability or glacial-period bottleneck size. Instead, spatial expansions and increased connectivity during favorable climates likely maintain diversity in the north while restriction to high elevations maintains relatively low diversity despite greater stability in southern regions. Results suggest genetic diversity gradients reflect long-term differences in Ne dynamics and also emphasize the unique effects of isolation on insular habitats for bumble bees. Patterns are discussed in the context of conservation under climate change.

publicJan 2024View details →

A lack of genetic diversity and minimal adaptive evolutionary divergence in introduced Mysis shrimp after 50 years

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publicJan 2023View details →

Whole genome demographic models indicate divergent effective population size histories shape contemporary genetic diversity gradients in a montane bumble bee

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opencc-zeroJan 2024View details →

High sexual display trait diversity without measured genetic divergence in a montane hybrid zone involving young species (Habronattus americanus subgroup, Araneae, Salticidae)

Genetic introgression, allele exchange across species boundaries, is a commonly recognized feature of animal evolution. Under such a paradigm contemporary contact zones provide first-hand and complementary insight into the geographic, phenotypic, and genetic details of introgression. Also, when mate choice phenotypes are conspicuous and variable in hybrids, contact zones provide potential insight into how sexual selection interacts with species boundary maintenance, particularly when postzygotic reproductive isolation is weak. The Habronattus americanus subgroup includes several recently evolved jumping spider species, with an estimated age of about 200,000 years, and substantial evidence for hybridization and introgression. We explored a contact zone involving H. americanus (Keyserling, 1885) and H. kubai (Griswold, 1979) on Mount Shasta, California, in alpine habitats that would have been unavailable (under ice) at the Last Glacial Maximum. We characterized morphological diversity within the contact zone, including the fine-scale geographic distribution of hybrid and parental individuals, and assessed genetic variation using ddRADseq data. Combined results indicate a lack of measured genomic differentiation between specimens with distinct morphologies, including individuals with phenotypes of the parental species. We identified a diverse array of hybrid morphologies, with phenotypic evidence for backcrossing, essentially forming a phenotypic bridge between parental taxa. The study area is characterized by more hybrid than parental individuals, with a significantly larger number of red-palped morphologies than white and/or yellow-palped morphologies; the novel, white-palped phenotype is perhaps transgressive. Overall, these results contribute to a better understanding of the expected ebb and flow of lineage interactions during the early stages of speciation.

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.

zenodo36/100

FIGURE 5 in A new species of Knodus (Characiformes: Characidae), with deep genetic divergence, from the Mearim and Munim river basins, Northeastern Brazil, and evidence for hidden diversity in adjacent river basins

FIGURE 5 | Geographical distribution of Knodus guajajara.

opencc-zeroSep 2023View details →

Data and Code for: Reproductive strategies and their consequences for divergence, gene flow, and genetic diversity in three taxa of Clarkia

Differences in reproductive strategies can have important implications for macro- and micro-evolutionary processes. We used a comparative approach through a population genetics lens to evaluate how three distinct reproductive strategies shape patterns of divergence among as well as gene flow and genetic diversity within three closely related taxa in the genus Clarkia. One taxon is a predominantly autonomous self-fertilizer and the other two taxa are predominantly outcrossing but vary in the primary pollinator they attract. In genotyping populations using genotyping-by-sequencing and comparing loci shared across taxa, our results suggest that differences in reproductive strategies in part promote evolutionary divergence among these closely related taxa. Contrary to expectations, we found that the selfing taxon had the highest levels of heterozygosity but a low rate of polymorphism. The high levels of fixed heterozygosity for a subset of loci suggests this pattern is driven by the presence of structural rearrangements in chromosomes common in other Clarkia taxa. In evaluating patterns within taxa, we found a complex interplay between reproductive strategy and geographic distribution. Differences in the mobility of primary pollinators did not translate to a difference in rates of genetic diversity and gene flow within taxa – a pattern likely due to one taxon having a patchier distribution and a less temporally and spatially reliable pollinator. Taken together, this work advances our understanding of the factors that shape gene flow and the distribution of genetic diversity within and among closely related taxa.

publicOct 2017View details →

Data from: Hidden diversity within the lizard genus Liolaemus: genetic vs morphological divergence in the L. rothi complex (Squamata:Liolaeminae)

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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 and Code for: Reproductive strategies and their consequences for divergence, gene flow, and genetic diversity in three taxa of Clarkia

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