Unravelling the climatic niche overlap of global sea turtle nesting sites: Impact of geographical variation and phylogeny

Abstract

AbstractAimIdentifying processes that determine climatic niche dynamics is difficult, especially for wide‐ranging species where niche conservatism might differ at different life stages. Evolutionary history shapes climatic niche, with populations of the same or phylogenetically close species occupying similar conditions. However, the geographical separation of populations also leads to niche evolution as an adaptive response to local conditions. Here, we use five sea turtle species (loggerhead, green, leatherback, hawksbill, olive ridley) to test whether short‐ (environmental adaptation) or long‐term (phylogenetic separation) evolutionary events determined the level of niche conservatism among distinct groups of nesting populations (termed Regional Management Units; RMUs) distributed across different ocean basins.LocationGlobal.MethodsWe estimated the climatic niche of 4,829 georeferenced nesting locations using air and sea surface parameters. We quantified niche overlap among RMUs of the same species at a global scale and examined how the geographical ranges of each RMU are correlated with niche similarity. We also investigated the extent of niche conservatism among RMUs of different species in the same ocean basin.ResultsWe found limited within‐species niche similarity of RMUs at a global scale, with geographical range having negligible impact (latitudinal overlap, range size asymmetries). We detected generally higher niche overlap between RMUs of different species located within the same ocean basin, where the geographical range had a stronger effect on niche similarity.Main conclusionsWe show that adaptation to local conditions potentially prevails over distant evolutionary events when considering the climatic niche of RMUs of the same species across different oceans. Because sea turtles, like other long‐distance migratory animals, occupy distinct climatic niches, our findings support the importance of understanding this phenomenon for different life stages, populations and species to preserve unique adaptations to different environments that might enhance future viability under climate change, as well as help identify key conservation areas.