Population structure, genetic diversity, and colonization history of the eastern pondmussel, Sagittunio nasutus, in the Great Lakes drainage

Abstract

1. The eastern pondmussel, Sagittunio nasutus (Bivalvia: Unionida), has declined in abundance and distribution in eastern North America over the last few decades.The declines are predominantly the result of infestation by invasive dreissenid mussels and changes in habitat. The species is now considered imperilled across large portions of its distribution, especially in the Laurentian Great Lakes region.2. The genetic diversity and structure of the remnant populations in the Great Lakes region were assessed using 10 newly developed microsatellite DNA loci for S. nasutus. Understanding the remaining populations can inform future management projects and determine whether the remnant populations have experienced a genetic bottleneck or a founder effect. We hope that this will inform the conservation of other species in regions founded by, and isolated from, a more genetically diverse source population or with disjointed geographical distributions.3. Focusing on the Great Lakes region, samples (n = 428) from 62 collection sites in 28 water bodies were collected. Across the locations sampled for S. nasutus 11 genetic populations were identified, with significant genetic differentiation among them. The genetic structure of the species was assessed, with genetic similarities among populations compared and with geographical routes of colonization and gene flow evaluated. 4. Initial colonization from the Atlantic coast into Lake Erie and Lake Ontario is evident, followed by colonization events into nearby inland rivers and lakes. Analyses found evidence of inbreeding in all but one population and evidence of past genetic bottlenecks or strong founder effects in all but four populations. This study deepens our understanding of the genetic past and present of this imperilled species, providing conservation suggestions for the future management of the species. K E Y W O R D S founder effects, genetic bottlenecks, Ligumia nasuta, management units, microsatellite DNA, phylogeography, population structure, rescue effect, Sagittunio nasutus, Unionidae

Genetic and morphological characterization of the freshwater mussel clubshell species complex (Pleurobema clava and Pleurobema oviforme) to inform conservation planning

“…Advance and retreat of glaciers during and after the Pleistocene had dramatic effects on topography, stream characteristics, and temperature regimes that likely influenced genetic diversity and structuring among North American freshwater populations, including fishes (Bernatchez & Wilson, 1998;Morrison et al, 2006;Near et al, 2001;Strange & Burr, 1997) and unionids (Elderkin et al, 2007(Elderkin et al, , 2008Hewitt et al, 2019;Inoue et al, 2013Inoue et al, , 2015Pieri et al, 2018;Scott et al, 2020;Zanatta & Harris, 2013). Although several studies of unionids have found that structuring generally follows major hydrogeologic basins (Galbraith et al, 2015;Mock et al, 2010), our STRUCTURE results for P. clava and P. oviforme do not align fully with present-day drainages.…”

“…Many previous studies of unionids have detected low levels of mtDNA divergence, with minimal divergence among haplotypes sampled across geographic ranges, while microsatellites provided increased resolution of population structuring (Chong et al, 2016;Jones et al, 2006;Kelly & Rhymer, 2005;Scott et al, 2020;Zanatta & Murphy, 2006, 2007. Similarly, analyses of nuclear microsatellite markers identified low to very high levels of among-population structuring among clubshell populations.…”

Comparative phylogenomics reveal complex evolution of life history strategies in a clade of bivalves with parasitic larvae (Bivalvia: Unionoida: Ambleminae)

“…However, an instantaneous transition in host use may be an unrealistic assumption. Another plausible explanation is a gradual host switch may have occurred as L. ochracea migrated to the Atlantic region through the St. Lawrence drainage, which aligns with putative dispersal routes of several mussel species (van der Schalie, 1963; Clarke, 1973; Haag, 2012; Scott et al, 2020). The only known native co‐occurrence of A. grunniens and M. americana is within the St. Lawrence drainage (Page and Burr, 2011), and multiple A. grunniens specialists (i.e., L. fragilis and P. alatus ) were historically distributed in the drainage (Strayer and Jirka, 1997).…”

Community eDNA metabarcoding as a detection tool for documenting freshwater mussel (Unionidae) species assemblages

“…Sampling waterbodies with well-characterized mussel communities enabled direct comparison of species detections from eDNA metabarcoding with those from long-term field surveys. Although we did not conduct concurrent physical surveys, the existing species assemblage data provided strong reference points for which species were likely to have recently shed DNA into each of those sites (Hoffman et al, 2018;Minke-Martin et al, 2015;Morris et al, 2015;Reid et al, 2018;Reid & Morris, 2017;Scott et al, 2020;Sheldon & Morris, 2018;Wright et al, 2017Wright et al, , 2019DFO unpubl. data).…”