Evidence from the past several decades shows that species distributions are changing in response to climate change. However, even the most robust studies attribute less than half of observed changes in species distributions to local climate factors, and foundational ecology considers climate as just one of many processes that determine species distributions. Biogeographic patterns in terrestrial and marine systems worldwide suggest that physical barriers to dispersal have played an important role in determining species range edges throughout evolutionary history. These barriers may impact a species’ ability to “track” climate change – i.e., to follow its preferred bioclimatic conditions through space by colonizing novel habitat beyond one range edge and/or receding from the other edge of its native range. In the oceans, marine current regimes can create strong biogeographic barriers by inhibiting larval dispersal in one or both directions along a coastline. This study investigates whether coastal marine species that rely on larval dispersal can track climate change across marine current-related biogeographic boundaries. We present a model of larval dispersal along a coastline that incorporates marine currents, life stages, dispersal modes, and moving suitable habitat (as a proxy for climate change).
Results/Conclusions
Biogeographic barriers driven by ocean currents inhibit the ability of a species to colonize new habitat along a coastline via larval dispersal, even if that habitat is highly suitable and the species’ native range is shrinking as a result of climate change. Species with a mobile adult stage may partially or fully compensate for this effect; sessile adults are more impacted. Paradoxically, species with long larval phases are the most strongly inhibited by these biogeographic barriers; unlike other species with short larval phases that occasionally colonize against prevailing currents via nearshore eddies, these species spend so long in the water column that they rarely escape the prevailing current regime. Marine biogeographic barriers may prevent species that rely on larval dispersal, especially sessile species with long larval phases, from tracking climate change. This process can be predicted for biogeographic barriers around the world and should be incorporated into analyses of observational data and predictive models for coastal marine ecosystems. The location and effect of these biogeographic barriers can help identify species that may get “stuck” and experience severe range contractions as a result of climate change without proactive conservation measures.