A low number of introduced marine species at low latitudes: a case study from southern Florida with a special focus on Mollusca

The anthropogenic transfer of non-indigenous marine species (NIMS) into new areas of the oceans is a key issue. Despite increasing research effort in recent years many fundamental questions remain to be answered before we can effectively manage the issue. One question is whether the greater munber of NIMS thus far documented in temperate waters is real or an artefact of fewer surveys being undertaken in tropical environments. Another one is whether poor taxonomic knowledge of the biodiverse tropics hides NIMS that actually occur there. Extensive taxonomic work in three Pacific localities (Guam, northern Western Australia and Singapore) has been collated in previous papers showing that thew are relatively few NIMS in these biodiverse environments. The present paper replicates investigations for a low latitude environment in southern Florida in the Atlantic Ocean. The focus area includes the extensive Florida Keys coral reef environment. the southern margin of the Everglades on Florida Bay and the major PortMiami. Only 48 NIMS were identified in a literature-based compilation of 4,615 species; 15 species were represented by isolated records and have not established populations, leaving only 33 NIMS that are established or whose status is unknown. Records for Mollusca, the group with the most species (1,153) in the compilation, were individually researched and taxonomically verified. It is argued that the relative paucity of NIMS is not a straightforward temperature-driven tropical/temperate issue, but instead there are biological factor(s) restricting the ability of NIMS to colonise biodiverse environments compared to less diverse areas.