Abstract
North American freshwaters are among the world’s most threatened ecosystems, and freshwater mussels are among the most imperiled inhabiting these systems. A critical aspect of conservation biology is delineating patterns of genetic diversity, which can be difficult when a taxon has been extirpated from a significant portion of its historical range. In such cases, evaluating conservation and recovery options may benefit by using surrogate species as proxies when assessing overall patterns of genetic diversity. Here, we integrate the premise of surrogate species into a comparative phylogeographic framework to hypothesize genetic relationships between extant and extirpated populations of Potamilus inflatus by characterizing genetic structure in co-distributed congeners with similar life histories and dispersal capabilities. Our mitochondrial and nuclear sequence data exhibited variable patterns of genetic divergence between Potamilus spp. native to the Mobile and Pascagoula + Pearl + Pontchartrain (PPP) provinces. However, hierarchical Approximate Bayesian Computation indicated that the diversification between Mobile and PPP clades was synchronous and represents a genetic signature of a common history of vicariance. Recent fluctuations in sea-level appear to have caused Potamilus spp. in the PPP to form a single genetic cluster, providing justification for using individuals from the Amite River as a source of brood stock to re-establish extirpated populations of P. inflatus. Future studies utilizing eDNA and genome-wide molecular data are essential to better understand the distribution of P. inflatus and establish robust recovery plans. Given the imperilment status of freshwater mussels globally, our study represents a useful methodology for predicting relationships among extant and extirpated populations of imperiled species.
Highlights
Due to anthropogenic alterations to the environment, the world is losing species at rates comparable to mass extinctions during major transitions of geological time periods [1,2]
Substitution models determined by ModelFinder for locus alignments in the STACEY analysis were: HKY + I for c oxidase subunit 1 (CO1), HKY + I for NADH dehydrogenase subunit 1 (ND1), JC for fem-1 homolog C (FEM1), F81 + I for UbiA, and K2P + I (=K80 + I) for
Our results suggest that the divergence between Potamilus spp. in the Mobile and Pascagoula + Pearl + Pontchartrain (PPP) occurred simultaneously and further support previously described biogeographic provinces [79]
Summary
Due to anthropogenic alterations to the environment, the world is losing species at rates comparable to mass extinctions during major transitions of geological time periods [1,2]. Diversity 2020, 12, 281 dominated landscapes [7,8,9], leading to extensive population decline of both common and rare species [4,6,10] Given these declines, establishing robust species-specific status assessments is essential toward future implementation of effective conservation and recovery strategies for these highly imperiled organisms [6,11]. Multiple studies have used comparative phylogeography to resolve the evolutionary history of aquatic taxa in the southeastern United States and showed concordance in phylogeographic clustering across co-distributed taxa [17,18,19] These examples have concentrated on relatively common species, and determining relationships among populations of imperiled species can be problematic when taxa have been extirpated from a significant portion of their historical range. The use of surrogate species (e.g., common species with similar life history characteristics used as proxies for imperiled species) is increasingly being used in conservation practices [20], but this methodology has not been explored in many freshwater taxa [21]
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