Oral Presentation Society for Freshwater Science 2025 Annual Meeting

Using comparative genomics to understand population-level effects of stream drying on a common mayfly family sampled across a continental aridity gradient.  (118779)

Samuel C. Silknetter 1 , Meryl C. Mims 1 , Daryl R. Trumbo 1 , Michael T. Bogan 2 , Brian A. Gill 2 , Albert Ruhi Vidal 3 , Carla L. Atkinson 4 , Arial J. Shogren 4 , Travis M. Apgar 3 , Zacchaeus G. Compson 5 , Kelsey D. Hollien 2 , Kyle Leathers 3 , Chelsea R. Smith 4 , Jacob D Dorris 4 , Shang Gao 2 , Thomas M. Neeson 6 , Megan C. Malish 6 , Daniel C. Allen 7
  1. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
  2. School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA
  3. Department of Environmental Science, Policy, & Management, University of California, Berkeley, CA, USA
  4. Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, USA
  5. Department of Biological Sciences, University of North Texas, Denton, TX, USA
  6. Department of Biology, University of Oklahoma, Norman, OK, USA
  7. Department of Ecosystem Science and Management, The Pennsylvania State University, State College, PA, USA

We are amid a global biodiversity crisis, and freshwater ecosystems are vulnerable to environmental change. Streams are particularly susceptible to fragmentation, with isolated populations of dispersal-limited organisms often leading to declines in genetic diversity that precede local extirpation. However, taxa adapted to naturally fragmented habitats, such as drying streams, may have strategies that increase gene flow. Even between closely related taxa, this may lead to differential effects on observed patterns of genetic diversity. To determine the population-level effects of stream drying, we generated genomic datasets using double-digest restriction-site associated DNA sequencing for multiple mayfly taxa in the widespread Baetidae family. We collected genomic data at five stream basins that span a range of aridity across the USA as part of the StreamCLIMES Project. We hypothesize that Baetidae populations in the most arid basins will experience greater fragmentation (measured as percent connectivity) and reduced genetic diversity. We will then use landscape genomic approaches to identify drivers of the observed differences in population genetic diversity. DNA barcoding indicated that each basin had 1-2 dominant taxa with enough samples (94 to 194 individuals per taxa; 4 to 11 sites per taxa) to proceed with landscape genomic analyses. After calculating measures of genetic diversity (i.e., heterozygosity, inbreeding, allelic richness, pairwise differentiation) for each taxon, we assessed population structure within basins by relating genomic diversity to geographic distances, including Euclidean and river network distances that account for fragmentation. Preliminary results suggest patterns of population genomic structure that differ by basin, but specific effects of drying and other drivers have yet to be fully investigated. By comparing the population genetic diversity and structure of Baetidae across basins that differ in aridity and levels of river network fragmentation, we can better understand to what extent stream drying may threaten genetic diversity of freshwater organisms.