Allozymic variation and biogeography of snapping shrimp (Alpheus) from the Gulf of Mexico and northwestern Atlantic coasts

Ambiguities in the identification and nomenclature of the Edwardsii group of Alpheus led to an investigation of allozymic variation in two sympatric snapping shrimps, Alpheus heterochaelis and A. angulatus, from the northern Gulf of Mexico and northwestern Atlantic coasts. Twelve allozyme loci were examined for 287 individuals. Electrophoretic variation was consistent with studies elsewhere in which the shrimps were morphologically differentiated into two groups representing A. heterochaelis and A. angulatus. Individuals were partitioned into two discrete groups, fixed for alternate alleles at seven loci. The remaining four loci were polymorphic, with each group exhibiting different allele frequencies. Genetic distance and similarity of the two groups wt re estimated at 1.729 and 0.192, respectiviely. Thr high degree of genetic distance between the two species contrasts with their high degree of morphological similarity described elsewhere. Clustering analyses for A. angulatus revealed a pattern consistent with biogeographic patterns suggested in other studies for the northern Gulf of Mexico and northwestern Atlantic coasts.