First record of the symbiotic snapping shrimp Alpheus immaculatus Knowlton & Keller, 1983 from Bermuda

Abstract The Bermudan Archipelago supports a high-latitude subtropical coral reef ecosystem ∼1500 km from the nearest major reef system in the Tropical Western Atlantic (TWA) and Greater Caribbean. Although isolated, Bermuda has low rates of marine endemism due to regular long-distance dispersal from the TWA via the Gulf Stream Current. Nevertheless, Bermuda’s coral reef biodiversity is a reduced subset of that in the Greater Caribbean, indicating that its isolation does limit some species from dispersing or establishing persistent populations. The Alpheus armatus Rathbun, 1901 species complex is a clade of five pistol snapping shrimp species that form obligate symbioses with sea anemones from the TWA and Greater Caribbean. Although their host anemones are abundant, no members of this complex are known from Bermuda. We provide the first report of the A. armatus species complex from Bermudan coral reefs. Using molecular approaches, we identified our observed individual as Alpheus immaculatus Knowlton and Keller, 1983. Phylogenetic and species delimitation analyses indicate that our A. immaculatus sample from Bermuda does not represent a cryptic lineage nor genetically differentiated population. Instead, we interpret this species to have arrived recently as a chance long-distance dispersal event. No other A. immaculatus individuals were observed, suggesting this species has not been able to establish a long-term population in Bermuda.