CLIMATE CHANGE AND MARINE MOLLUSKS: A TALE OF INVASIONS, IMMIGRATION AND EXTIRPATION

We examine the potential responses of 15 extant species of mollusks in the Atlantic and Gulf Coastal Plains to future environmental changes using an ecological niche modeling (ENM) analytical framework. Numerous studies have examined potential responses by the terrestrial biota to future climate changes, but a paucity of data exists on effects in the oceanic realm. Key neo- and paleontological questions are the ecological and evolutionary challenges that climate changes pose to species, and what the future holds for our planet and its biota. In ENM, species geographic occurrence points and environmental variables are related using machine-learning algorithms to make inferences about the environmental requirements of a species, which can then be projected onto geography. ENM models can also be projected onto future climate scenarios. In this study, we use two modeling algorithms and project our models onto three different climate change scenarios for 2021-2040, 2041-2060, and 2081-2100. Our results predict climate change will induce potentially significant decreases (at least 15%) in available suitable habitat in 11 of the 15 species modeled. The simplistic assumption that tropical species will shift towards the poles was supported in only 5 of the 15 species. Our results further indicate species will respond individualistically to climate change when tracking their preferred environment. Thus, some species will be relatively unaffected and others will undergo significant range expansion or contraction: faunas will not respond in unison. Three species may suffer up to 70% reduction in niche space, fragmenting populations and raising concerns of species-wide extinction. This is particularly alarming, as all 15 species have persisted for several millions of years, weathering climatic oscillations in the Pleistocene as well as the last thermal maxima (~3 mya), when global temperatures were sustained at levels we may see at the end of this century. Conversely, such fragmentation may also provide a means for inducing subsequent speciation. Using ENM to study future biotic effects of climate change may also serve as a microcosm for understanding how past episodes of climate change caused extinction and speciation.