Meeting Abstract

64.6  Tuesday, Jan. 6  Morphological, Physiological, and Genetic Variation in the Red-Jointed Fiddler Crab, Uca minax (Le Conte) WARWICK, A.R.; HOPKINS*, M.J. ; BERENDZEN, P.B. ; THURMAN , C.L. *; University of Northern Iowa; *University of Chicago thurman@uni.edu

Due to its absence on peninsular Florida, Uca minax is unusual in having a disjunct distribution along the southeast coast of the United States. To understand the impact of isolation, we examined carapace morphology, osmoregulation, and gene sequences for cytochrome oxidase-1 (CO1) and internally transcribed sequence (ITS-1) across the species range. Osmoregulation and mean hemolymph isotonic concentrations were identical for both Atlantic and Gulf populations. The variation of 23 carapace landmarks was assessed by principal components analysis. Although Goodall’s F-test indicates a significant difference between Gulf and Atlantic populations, the magnitude is small. The average difference is less than species with contiguous populations and is much smaller than the differences between U. minax and its sympatric relatives U. longisignalis and U. pugnax. Samples of CO-1 and ITS-1 genes from 15 sites revealed 72 unique CO-1 and 42 ITS-1 haplotypes. Phylogenetic analyses were performed on haplotypes and topologies constructed using Bayesian analyses for each gene. No genetic difference between the Gulf and Atlantic populations was found. Although haplotypes are shared, no geographic structure was evident. Most variation in CO-1 and ITS-1 was explained by differences within populations rather than among Gulf and Atlantic populations. Analyses of demographic parameters indicate a greater effective population size for the Atlantic population and separation of the two populations occurred only recently. This suggests a common refugium population in Floridia during Pleistocene glaciation. Following retreat of the ice, populations diverged and migrated to their current distribution. These findings suggest that although U. minax populations are disjunct, they are currently not substantially different in morphology, physiology or genetics.