Phylogeography and population genetics of a headwater-stream adapted crayfish, Cambarus pristinus (Decapoda: Cambaridae), from the Cumberland Plateau in Tennessee

Abstract

Assessments of genetic diversity for imperiled species can provide a baseline for determining the relative impacts of contemporary anthropogenic threats (e.g., habitat fragmentation) on population connectivity and identify historical factors contributing to population structure. We conducted a population genetics and phylogeographic assessment of the imperiled Pristine Crayfish (Cambarus pristinus) sampled throughout its range encompassing two morphologically distinct forms. Pristine Crayfish exhibit a disjunct distribution throughout lower order tributaries suggesting they are headwater-adapted species. The two morphologically distinct forms of the Pristine Crayfish are found in the upper Caney Fork (nominal Caney Fork form) and the Big Brush Creek and Cane Creek systems (Sequatchie form). We used 19 microsatellite loci and the cytochrome oxidase subunit I (COI) gene to assess population connectivity and genetic diversity of the Pristine Crayfish. Haplotypes recovered from the COI gene revealed that historic connectivity was maintained within each form of the Pristine Crayfish. However, the divergence between forms was higher (2.3%) than within forms (< 2.0%), suggesting each form is on an independent evolutionary trajectory, supporting recognition of the Sequatchie form as a distinct taxon. Microsatellite analyses for the Caney Fork form recovered a high degree of population isolation and support for six genetically isolated population. In addition, genetic diversity metrics per population and for the Caney Fork form were low suggesting that the Caney Fork form is at an increased risk of extinction under anthropogenic disturbances. We suggest that each form receive continued listing protection and conservation resources and that the Sequatchie form be treated as a unique taxon.