CRAFT, J.D.**; SANTOS, S.R.; Auburn University; Auburn University: Phylogeography of Halocaridina rubra: Discerning relatedness between populations of an endemic Hawaiian shrimp
The Hawaiian Islands have the largest concentration of anchialine habitats in the world. These coastal ecosystems are typically small land-locked pools whose water level fluctuates with daily oceanic tidal oscillations. Water movement to and from such pools occurs beneath the surface via a hydrological vascular system. The numerically and geographically dominant organism of these environments is Halocaridina rubra, an endemic atyid shrimp. Although previous work has documented the life history of H. rubra, the genetic diversity, population structure and phylogeography of this shrimp has never been explored. Understanding the relationships between H. rubra populations is of importance in light of urbanization and exotic species introductions that are leading to the rapid destruction of anchialine habitats. We investigated the relationships between H. rubra populations of the Hawaiian archipelago using mitochondrial cytochrome oxidase I (COI) DNA sequences. A survey of 18 populations (422 individuals) spanning the islands of Hawaii, Maui and Oahu revealed 187 haplotypes. Significant genetic structure between populations suggests that little to no migration or gene flow is regularly occurring over large (>30 km) geographic distances. Seven genetically diverged (~3-10%) lineages were recovered from this sampling; although further work is required to define the taxonomic status of these lineages, these divergences suggest isolation over significant time-spans and the possibility of subsequent speciation. The intrinsic uniqueness of anchialine environments compounded by the genetic distinctiveness of most H. rubra populations has important implications for conservation of the species and their habitats.