LEE, T.*; � FOIGHIL, D.; Univ. of Michigan; Univ. of Michigan: Placing the Floridian Marine Genetic Disjunction into a Regional Evolutionary Context Using the Scorched Mussel, Brachidontes exustus, Species Complex

The well-documented Floridian Gulf/Atlantic genetic disjunction provides an influential example of presumed vicariant cladogenesis along a continental coastline for major elements of a diverse nearshore fauna. However, it is unclear if it represents a local anomaly for regionally distributed morphospecies, or if it is merely one of many such cryptic phylogenetic splits. We aimed to place the scorched mussel Gulf/Atlantic genetic disjunction into a regional phylogenetic perspective by incorporating genotypes of nominal conspecifics sampled throughout the Caribbean Basin as well as those of eastern Pacific potential geminate species. Our results show it to be one of multiple latent regional genetic disjunctions, involving five cryptic Caribbean species. Disjunctions involving three stem lineages predate formation of the Isthmus of Panama, although four of the five cryptic species have within-Basin sister relationships. Surprisingly, the Atlantic clade was also found to be widespread in the southern Caribbean, and a northward range extension after the last glacial maximum was suggested for Atlantic coast-specific genotypes. Our new data seriously undermine the hypothesis of a Floridian vicariant genesis and imply that the scorched mussel Gulf/Atlantic disjunction represents a case of geographic and temporal pseudocongruence. All five Caribbean Basin cryptic species exhibited an intriguing pattern of predominantly allopatric distribution. A number of lines of indirect evidence favor the hypothesis that this pattern of distribution is maintained primarily by post-recruitment ecological filters rather than by oceanographic barriers to larval-mediated gene flow.