Cryptic diversity within and amongst spring-associated Stygobromus amphipods (Amphipoda: Crangonyctidae)

Multiple species of troglomorphic, spring-associated Stygobromus amphipods, including the endangered, narrow-range endemic Stygobromus pecki, occupy sites in the Edwards Plateau region of North America. Given the prevalence of cryptic diversity observed in disparate subterranean, animal taxa, we evaluated geographical genetic variation and tested whether Stygobromus contained undetected biodiversity. Nominal Stygobromus taxa were treated as hypotheses and tested with mitochondrial sequence cytochrome oxidase C subunit 1, nuclear sequence (internal transcribed spacer region 1), and AFLP data. Stygobromus pecki population structure and diversity was characterized and compared with congeners. For several Stygobromus species, the nominal taxonomy conflicted with molecular genetic data and there was strong evidence of significant cryptic diversity. Whereas S.pecki genetic diversity was similar to that of congeners, mitochondrial data identified two significantly diverged but sympatric clades. AFLP data for S.pecki indicated relatively recent and ongoing gene flow in the nuclear genome. These data for S.pecki suggest either a substantial history of isolation followed by current sympatry and ongoing admixture, or a protracted period of extremely large effective population size. This study demonstrates that Edwards Plateau Stygobromus are a complex, genetically diverse group with substantially more diversity than currently recognized.(c) 2013 The Linnean Society of London