SPECIES INVASIONS DURING THE LAST INTERGLACIAL PERIOD & PREDICTIONS FOR TODAY IN CALIFORNIA’S SHALLOW MARINE ENVIRONMENTS

The Last Interglacial Period (120,000 years ago; “LIG”) in southern California is marked by regional climate warming and a spike in tropical marine species invasions. As contemporary California’s climate continues to change, understanding the ecological attributes that distinguish LIG invasions may offer valuable insight into coming ecological invasions and displacements. Here we utilize newly compiled databases of LIG fossil and present-day mollusc (shelled gastropods and bivalves) species distributions to address two questions: 1) what aspects of contemporary species’ environmental and geographic niches best characterize LIG invasions? 2) which species are most likely to invade southern California in the coming decades?

We find that aspects of geographic distribution (latitudinal range and oceanic island occupancy) are stronger indicators of LIG species invasions than seasonal and annual environmental (chlorophyll α concentration and sea surface temperature) ranges. Together these findings suggest that abiotic environmental factors alone are insufficient to explain past range changes and that latent attributes of species interactions and dispersal captured by geographic distributions play critical roles in climate mediated invasion. We present the results of a series of general linear models trained on LIG invasions; the results of this analysis highlight key species that may soon invade California’s shores.