High levels of mitochondrial DNA sequence divergence among isolated populations of Fontigens (Truncatelloidea: Emmericiidae) in eastern USA

Populations of the minute emmericiid gastropod Fontigens inhabit isolated springs, caves and groundwaters widely scattered across eastern and midwestern USA. Nine species are currently recognized, with a tenth species, Fontigens cryptica, of uncertain status. Here, we survey intrapopulation, interpopulation and interspecific sequence variation of cytochrome c oxidase subunit I among six of the nine species (13 populations, 87 individuals), documenting up to 14.4% sequence divergence among conspecific populations. Interspecific divergence ranges from 8.7% to 21.9%. We also include in our analysis a single putative individual of F. cryptica, recently sampled from Kentucky, evaluating whether the population it represents may be genetically distinct. Fit within a larger phylogenetic context, the 14.4% sequence divergence demonstrated between this individual and its nearest neighbour, F. bottimeri sampled from Washington, DC, supports the specific status of F. cryptica.