ABSTRACT
Malacostraca is a highly diversified class of crustaceans. Of the estimated 26,000 malacostracan species described, about 6,000 inhabit a plethora of freshwater habitats worldwide. The Mediterranean Region has been recognized as one of the 25 most important biodiversity and endemism hotspots and its islands are considered to be natural laboratories of evolution. Even though the Mediterranean Region contains roughly 6% of freshwater malacostracan taxa, knowledge about the freshwater fauna of this area is incomplete and studies are scarce. Here we provide, arguably, the first extensive study on the freshwater malacostracan fauna of the Mediterranean Islands. The Mediterranean Island freshwater houses 182 species in five orders (Amphipoda, Isopoda, Thermosbaenacea, Bathynellacea, Decapoda), representing 51 genera and 27 families. More than half are endemic. Even though the islands cover only about 5% of the Mediterranean Region area and about 0.2% of the whole Palearctic, the overall number of species corresponds to 25% of all malacostracan species reported from the region and more than 8% of Palearctic species. The number of reported insular species is high, and we expect this number will grow. However, freshwater biota extinction rates may be much higher than terrestrial organisms. Planning reasonable and efficient strategies to protect local, especially endemic, freshwater fauna are urgently needed.
