Fine‐scale phylogeography reveals cryptic biodiversity in Pederson's cleaner shrimp,Ancylomenes pedersoni(Crustacea: Caridea: Palaemonidae), along the Florida Reef Tract

Abstract

AbstractPopulations of continuously distributed marine organisms that disperseviapelagic larvae are often assumed to exist in a state of genetic panmixia because of their potential ability for long‐distance dispersal. However, obligate symbionts may have more restricted gene flow due to recruitment limitations, making host specificity an important potential driver of biodiversity. To explore the tension between broad dispersal ability and limited recruitment potential, we used sequences of mtDNA cytochromecoxidase subunit I (COI) to assess the fine‐scale phylogeography of the cleaner shrimp,Ancylomenes pedersoni, an obligate symbiont of sea anemones, along 300 km of the Florida Reef Tract (FRT). The results indicate high genetic diversity withinA. pedersonipopulations along the FRT. Pair‐wise ϕSTvalues indicate significant genetic structuring between northern (Fort Lauderdale and Upper Keys) and southwestern (Lower Keys) populations, with significant isolation by distance. Two divergent COI haplotype lineages were detected through statistical parsimony analysis: one evenly distributed across the entire FRT (Clade 1) and one found primarily in two sample localities in the Lower Keys (Clade 2). Phylogenetic analyses using 16S‐rDNAindicates that this genetic diversity is of paraphyletic origin, and possibly the result of multiple colonization events. These results reveal a complex demographic and evolutionary history forA. pedersonipopulations and provide the first evidence of highly divergent intra‐specific lineages independently colonizing the FRT. Because the FRT is a highly impacted coral reef system, understanding phylogeographic patterns along it has value beyond documentation of the factors that generate genetic diversity in tropical reef systems: these data are critical for creating scientifically based management strategies.