Not any two will do: DNA divergence and interpopulation reproductive compatibility in the simultaneous hermaphroditic shrimp Lysmata wurdemanni

Abstract

We studied the molecular population structure of the hermaphroditic caridean shrimp Lysmata wurdemanni (Gibbes, 1850), which is distributed along the east coast of the USA and in the Gulf of Mexico. Four populations within the reported range were sampled: North Carolina (NC), Florida east coast (FLE), Florida Keys (FLK), and Texas (TX). Of the 3 populations of L. wurdemanni tested for interpopulation breeding (FLE, FLK, TX), only the FLE × FLK cross was successful. Both Florida populations failed to successfully hybridize with the Texas population during the experimen- tal period. Additionally, there appears to be strong directionality between Florida and Texas crosses: when TX females crossed with either male FLK or FLE shrimps, few eggs were present and no larval hatching occurred, whereas crosses between FLE or FLK females and TX males produced embryos, but no viable larvae were produced during the experimental period. Genealogical analyses of the mitochondrial genes cytochrome oxidase subunit I (COI) and the large subunit of ribosomal RNA (16S rRNA) genes yielded distinct and highly supported clades for each of the FLE, FLK, and TX pop- ulations. High pairwise FST values between TX versus FLK, TX versus FLE, and FLK versus FLE sug- gested that the populations are genetically disconnected. The NC and FLE populations could not be distinguished phylogenetically. This is an example of a marine species for which the potential for lar- val dispersal is predominantly unrealized given the observed absence of gene flow and the strong reproductive isolation between populations on the southeast coast of the United States and on the Gulf coast.