Climate, Continental Breakup and Habitat Shape Global Diversification and Biogeography of Turtles (Testudines)

Abstract

Aim Evaluate the relative contributions of palaeotemperature, palaeogeographic reconfiguration, and habitat heterogeneity to the diversification and biogeographic history of turtles (Order Testudines) from the Triassic to the present. Location and Time Period Global; Triassic–Recent. Taxa Extant Testudines (time‐calibrated phylogeny sampling ~286 species). Methods We combined a near‐complete, time‐calibrated phylogeny with complementary macroevolutionary and biogeographic methods. Diversification dynamics were explored using time‐ and temperature‐dependent models (RPANDA), rate‐shift analyses (BAMM), and state‐ and geography‐dependent frameworks (GeoHiSSE). Historical ranges were inferred with multiple BioGeoBEARS models. Associations between reconstructed speciation rates and independent palaeotemperature records were tested using Pearson's correlation and detrended cross‐correlation analysis (DCCA). Habitat categories (aquatic, amphibious, terrestrial) were coded for all taxa and explicitly incorporated into state‐dependent models to assess their influence on diversification dynamics. Results Diversification dynamics of Testudines are consistent with interacting effects of palaeoclimate, plate tectonics and habitat. Testudines' diversification positively tracks palaeotemperature overall, but the sign and strength are clade‐specific: some lineages speciate more in cooler intervals, others in warmer ones. Ancestral‐range reconstructions identify multiple well‐supported range shifts and vicariance events that are temporally concordant with major episodes of continental fragmentation. State‐dependent analyses recover distinct diversification regimes among aquatic, amphibious and terrestrial lineages, indicating that habitat affinity modulates macroevolutionary responses to climatic and tectonic forcing. Main Conclusions No single factor alone explains turtle diversification through deep time. Instead, climatic transitions (both cooling and warming), tectonic reconfiguration of landmasses, and habitat‐specific ecology and dispersal capacity were associated with the timing and geography of lineage accumulation in Testudines. Our results indicate that the refugial hypothesis is not universally supported across Testudines. Instead, support is lineage dependent, with some clades diversifying during cooler intervals and others during warmer periods. Moreover, the results indicate that habitat heterogeneity has played a key role in promoting speciation across the group.

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