Abstract 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.

Abstract The mid-Piacenzian Warm Period (mPWP: 3.3–3.0 Ma) is the most recent geological analogue of ongoing climate change and has been the subject of considerable interest for numerical models of the climate system. To verify the effect of the mPWP on diversity and temporal turnover of marine benthic communities, we evaluated changes in species-level abundance and the composition of Mediterranean Pliocene molluscs prior, during and after the mPWP. The Pliocene onshore–offshore gradient in species composition did not change during the mPWP (and continued basically unchanged up to the present day in the Mediterranean Sea), with most dominant species occupying the same rank in a given environment. During the mPWP, species evenness generally increased towards offshore environments. Within the three time intervals, temporal similarity is greater in offshore environments, except during the mPWP when offshore communities also exhibited greater dissimilarity. The temporal turnover in composition decreased again with depth as global temperatures decreased after the mPWP. The structure of mPWP communities suggests that warming and sea-level rise contributed to the expansion of vegetated bottoms (onshore) and shelly and coralligenous bottoms (offshore). Although the effects of mPWP warming did not change the onshore–offshore gradient in the long term, its effect disproportionately affected deeper environments, in contrast to colder climate regimes.