Distributional Range Shifts Caused by Glacial–Interglacial Cycles: A Review on Timing, Main Processes, and Patterns of Late Pleistocene Marine Dispersal by Invertebrates in the NE Atlantic

The fossil record of marine molluscs has been used as evidence to test marine island biogeography theories and to complement the evolutionary patterns of biodiversity and endemicity found in oceanic islands and archipelagos. Although long-distance dispersal patterns have been the subject of several studies, important questions may still be posed. For instance, are these processes random, or do they show distinct patterns? And are they restricted to “windows of opportunities”, or do they occur continuously? In the NE Atlantic, the dispersal of tropical species towards higher latitudes associated with the last interglacial period is a well-known phenomenon. However, the most probable dispersal route remains a matter of debate. To test these ideas, we used the Atlantic and Mediterranean last interglacial fossil records, and compared the present geographic distribution of shallow-water marine molluscs with that registered during the last interglacial episode, aiming to detect changes. Our results show that 27 species became extinct during the course of the last glacial episode, and that 55 marine mollusc species (43 gastropods and 12 bivalves) are ecostratigraphic indicators for the MIS 5e fossiliferous deposits in the Macaronesian archipelagos, the Atlantic coasts of Morocco, and the Mediterranean. Finally, we provide arguments for the timing of dispersal, which occurred during a restricted “window of opportunity” associated with the inception of the last interglacial, and for the most probable route of dispersal of the tropical species, most of them denoting a Cabo Verdean origin.