Worldwide molecular phylogenetics of the <i>Alpheus brevirostris</i> (Olivier, 1811) group (Decapoda: Caridea: Alpheidae)

Abstract Snapping shrimps in the genus Alpheus Fabricius, 1798 have long been a model system in which to study symbiotic relationships, especially the mutualism between burrowing shrimps and goby fishes. There has never been a comprehensive worldwide phylogeny of goby-dwelling snapping shrimp, however, hindering evolutionary studies of these symbioses. We examine phylogenetic relationships in the Alpheus brevirostris (Olivier, 1811) group, which is comprised of primarily burrowing species of snapping shrimps, many of which live in mutualistic partnership with gobies, and contains many of the most well-studied taxa in goby-shrimp symbioses. We first delimited cryptic species using COI data, which indicated multiple cryptic species of Alpheus. We then constructed a multi-locus phylogeny of species in the A. brevirostris group and several closely related species of Alpheus, and used fossil and transisthmian calibration points to construct a chronogram and date the origins of major clades. Our phylogeny confirmed previous work indicating the A. brevirostris group was paraphyletic, grouping in three major clades which diverged between 11.2 to 16.9 mya. Together, these data provide a phylogenetic framework for future taxonomic and evolutionary work on the origins and extent of the shrimp-goby and shrimp-echiuran symbioses.