Biodiversity change and extinction risk in Plio-Pleistocene Mediterranean bivalves: the families Veneridae, Pectinidae and Lucinidae

Understanding species vulnerability to extinction is one of the goals of conservation. Here we analyse a dataset of Plio-Pleistocene Mediterranean bivalve occurrences (families Veneridae, Pectinidae and Lucinidae), to reconstruct biodiversity change through time, and to test whether species occurrence frequency, geographical range and habitat specialization explained species survival or extinction. We found that biodiversity loss started soon after the mid-Piacenzian warming Period, at c. 3.0 Ma, and continued as climate progressively cooled, up to the Gelasian. It was more gradual than expected, as some species found a temporary refugium in the warmer, eastern Mediterranean. Extinction was more intense for the epifaunal, mobile pectinids, compared to the infaunal, siphonate venerids and lucinids. Occurrence frequency, geographical range and habitat specialization were good predictors of species extinction for the Veneridae and the Lucinidae. For the Pectinidae habitat specialization was a good predictor of extinction, but not occurrence frequency and geographical range, as also some common and geographical widespread Pliocene species became extinct. In this family, extinction risk was better predicted by latitudinal range than geographical range. Habitat loss due to the fragmentation of carbonate palaeoenvironments and high metabolic rates related to large body size also played a role in pectinid extinction.