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Small fish, large river: surprisingly minimal genetic structure in a dispersal-limited, habitat specialist fish

Citation

Washburn, Brooke (2021), Small fish, large river: surprisingly minimal genetic structure in a dispersal-limited, habitat specialist fish, Dryad, Dataset, https://doi.org/10.5061/dryad.xwdbrv19g

Abstract

Genetic connectivity is expected to be lower in species with limited dispersal ability and a high degree of habitat specialization (intrinsic factors). Also, gene flow is predicted to be limited by habitat conditions such as physical barriers and geographic distance (extrinsic factors). We investigated the effects of distance, intervening pools, and rapids on gene flow in a species, the Tuxedo Darter (Etheostoma lemniscatum), a habitat specialist that is presumed to be dispersal-limited. We predicted that the interplay between these intrinsic and extrinsic factors would limit dispersal and lead to genetic structure even at the small spatial scale of the species range (a 38.6 km river reach). The simple linear distribution of E. lemniscatum allowed for an ideal test of how these factors acted on gene flow and allowed us to test expectations (e.g., isolation-by-distance) of linearly distributed species. Using 20 microsatellites from 163 individuals collected from 18 habitat patches, we observed low levels of genetic structure that were related to geographic distance and rapids, though these factors were not barriers to gene flow. Pools separating habitat patches did not contribute to any observed genetic structure. Overall, E. lemniscatum maintains gene flow across its range and is comprised of a single population. Due to the linear distribution of the species, a stepping stone model of dispersal best explains the maintenance of gene flow across its small range. In general, our observation of higher than expected connectivity likely stems from an adaptation to disperse due to temporally unstable and patchy habitat.

Methods

PCR products were genotyped using an ABI3730 sequencer with LIZ600 as the size standard at the University of Florida Interdisciplinary Center for Biotechnology Research. Allele sizes were scored automatically using the panel editor function in GeneMarker v1.6 (SoftGenetics LLC) and then confirmed manually. Any allele that did not fit the expected repeat pattern for that locus was closely examined, and then, if necessary, edited manually or re-amplified and re-genotyped. To ensure consistency of allele sizes across reactions, three positive controls were included on each genotyping run.

Usage Notes

Missing alleles are denoted with a 0. The spreadsheet includes each sampled individual’s identification name, and the individual’s corresponding locality and reach numbers. Each locus is spread over two columns (denoted as Elem0##) and the allele calls for each individual is given for each locus and individual.

Funding

U.S. Fish and Wildlife Service, Award: C-15-0410

U.S. Army Corps of Engineers

Austin Peay State University