A new species rises from beneath Florida: molecular phylogenetic analyses reveal cryptic diversity among the metapopulation of Crangonyx hobbsi Shoemaker, 1941 (Amphipoda: Crangonyctidae)

The phylogenetic structure of 23 populations of Crangonyx hobbsi, a stygobitic amphipod species endemic to the Floridan aquifer, is detailed. Molecular genetic analyses (based on three genes the nuclear 18S rDNA, 28S rDNA, and mitochondrial 16S rDNA) point to the presence of at least two phylogenetic clades within the aquifer. These clades align into two major zoogeographic regions, the Northern Suwannee River Basin and the Coastal and Central Lowlands in the Florida peninsula. Three species delimitation models indicate that the Northern Suwannee River Basin Clade represents a species level differentiation from C. hobbsi sensu stricto. Morphological analyses support the molecular analyses, revealing the presence of several taxonomically significant differences between the two species, including presence/absence of calceoli on the second antennae of males and differences in telson shape in both sexes. Additionally, the molecular diversity of C. hobbsi sensu stricto was shown to be surprisingly variable, suggesting the potential presence of additional diversity within the taxon.