101-7 Mobility modulated marine latitudinal diversity gradients across the end Permian and end Triassic mass extinctions

Abstract:

The latitudinal diversity gradient (LDG) is one of the most pervasive macroecological patterns of the biosphere, but its origins and drivers remain debated. The strength and direction of LDGs vary among modern marine invertebrate functional groups, raising the question of whether such groups also responded differently to environmental crises in deep time. Here, we used global marine fossil occurrences from the Paleobiology Database and Bayesian birth–death models to reconstruct genus-level diversity and diversification dynamics in equatorial and non-equatorial regions from the Late Permian to the Early Jurassic, comparing mobility groups across the end-Permian and end-Triassic mass extinctions. Our results show that marine LDGs shifted from a steep equatorial diversity peak in the Late Permian to a shallower gradient after the end-Permian extinction, recovered during the Middle Triassic, and inverted after the end-Triassic extinction. These trajectories differed among mobility groups. Swimming taxa exhibited a nearly flat LDG after the end-Permian extinction and a persistent inverse LDG after the end-Triassic event. Motile benthic taxa retained a strong equatorial diversity peak after the end-Permian crisis but also developed an inverse LDG after the end-Triassic extinction. Sessile taxa showed weakened gradients after both crises but did not develop a persistent inverse LDG. These results demonstrate that dispersal ability might modulate how marine invertebrates responded geographically to environmental disruptions, while their contrasting responses to the two crises suggest that the ecological and environmental controls on marine LDGs were not constant through time.

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