Shifting seas: the impacts of Pleistocene sea‐level fluctuations on the evolution of tropical marine taxa

Abstract Aim Pleistocene glacial cycles reduced global sea level by up to 130 m below present levels. These changes had profound impacts on coastal marine life, including a reduction of habitable area, changes in ocean currents, and shifts in water column thermal dynamics. We provide a comprehensive review of the impact of glacial sea‐level changes during the Pleistocene on tropical coastal marine life and a set of maps showing how coastlines worldwide changed during periods of low sea levels. Location We focused on coastal marine taxa within tropical latitudes, with deeper coverage of the world's major coral reef biogeographical provinces. Methods We examined recent and historical literature that alluded to the effects of Pleistocene sea‐level fluctuations in a variety of common marine clades. Data for shelf habitat area and map construction were obtained from the NOAA ETOPO 1 database, with final manipulations carried out in Adobe Illustrator CS 6. Results Drops in sea level led to a decrease in available coastal habitat and fragmented populations in many taxa, potentially resulting in high population genetic structuring. Habitable shelf area during sea‐level lows was reduced as much as 92% from present‐day values in some regions. Genetic evidence of population bottlenecks can be seen in many coastal marine taxa worldwide. Main conclusions Pleistocene sea‐level fluctuations seem to be linked to population bottlenecks worldwide, and influenced connections among populations separated by barriers that are affected by sea levels. Despite decreased habitat availability, very few species became extinct, and several species may have been formed due to restrictions in water (and consequently larval) flow between regions that are now connected. A variety of interdisciplinary studies have significantly increased our understanding of how Pleistocene sea‐level changes have shaped the marine landscape that we see today.