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

Abstract

Aim Identifying 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. Location Global. Methods We 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. Results We 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 conclusions We 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.

Do long‐distance migratory birds track their niche through seasons?

“…Third, we found support for increased niche tracking in species with larger range sizes but no support for increased niche tracking with wider niche breadth. Large range sizes increased the probability of finding comparable environments in opposing seasons for both predictor sets which is in line with previous findings on migratory sea turtle species (Almpanidou, Schofield, & Mazaris, ). Such a positive effect of range size, after controlling for statistical bias through similarity tests, could indicate other biotic controls on seasonal niche tracking.…”

Climatic niche evolution in turtles is characterized by phylogenetic conservatism for both aquatic and terrestrial species

“…More importantly, under the assumption of climatic niche conservatism, another recent study suggested that turtle species richness and distribution may decrease as a result of climate change affecting species' climatic niches (Ihlow et al., ). However, no previous study has evaluated climatic niche evolution for the whole group of nonmarine turtles (but see Almpanidou, Schofield, & Mazaris, for a general evaluation of niche conservatism in sea turtles) and climatic niche comparisons conducted so far have been mainly focused on invasive species (Liu et al., ; Rödder, Schmidtlein, Veith, & Lötters, ; Rodrigues, Coelho, & Diniz‐Filho, ; Rodrigues, Coelho, Varela, & Diniz‐Filho, ) with mixed results of niche conservatism and shifts. Therefore, studying niche evolution patterns in turtles represents an interesting opportunity with theoretical (understanding whether species habitat could influence climatic niche evolution) and conservation (understanding whether turtles could be able to deal with anticipated climatic changes) implications.…”

Marine Threats Overlap Key Foraging Habitat for Two Imperiled Sea Turtle Species in the Gulf of Mexico

“…We further demonstrate the need for conservation of sites that have key critical foraging habitat for two imperiled sea turtle species (following on Hart et al, 2012). Lastly, another set of major threats not included in this analysis are those currently occurring and predicted from climate change (e.g., Almpanidou et al, 2017). It will be important to track changes and shifts in both sea turtle habitat-use patterns and threat levels in these and other sea turtle foraging "hot spots" as well as to assess how impact weights of existing threats may fluctuate due to climate change in the future.…”