Meeting Abstract

4.2  Jan. 4  Potential speciation in anchialine environments: the roles of life history and geology SANTOS, S.R.; Auburn University santos@auburn.edu

Anchialine habitats, land-locked bodies of mixohaline water that fluctuate with the tides but have no surface connection to the sea, are known from around the world. A wide variety of organisms exploit anchialine environments, with many being endemic to these habitats. However, the mechanism(s) driving speciation in this unique niche have not been defined. This is particularly significant in light of the negative impact these habitats and their biota have experienced from anthropogenic causes such as coastal development and the human-mediated introduction and spread of exotic species. To explore the forces influencing the speciation of anchialine organisms, populations of the endemic atyid shrimp Halocaridina rubra were examined from across their range in the Hawaiian archipelago. Seven distinct mitochondrial lineages were identified from a sampling of over 600 individuals from ~40 habitats on three islands (i.e., Oahu, Maui and Hawaii), with the level of genetic divergence between lineages implying isolation over significant time-spans (~1-6 million years). In most cases, mitochondrial lineages of Halocaridina are compartmentalized in different aquifers by the rift zones of an island’s volcanoes, leading to nearly perfect isolation (i.e., F_ST~1) between populations. Although Halocaridina produces free-swimming lecithotrophic zoeae that can remain in the plankton for 24�37 days, long distance oceanic dispersal appears to be rare in this shrimp, suggesting interisland dispersal and/or colonization occur on evolutionary, rather than ecological, timescales. Further work is required to define the taxonomic status of these mitochondrial lineages; however, the level of genetic divergence between them suggests that Halocaridina represents a cryptic species complex and elicits questions on how best to conserve these �species� and their habitats.