Biogeographic response of marine plankton to Cenozoic environmental changes

Abstract

In palaeontological studies, groups with consistent ecological and morphological traits across a clade’s history (functional groups), afford different perspectives on biodiversity dynamics than (functional groups), afford different perspectives on biodiversity dynamics than do species and genera, which are evolutionarily ephemeral. We analyze Triton, a global dataset of Cenozoic macroperforate planktonic foraminiferal occurrences to contextualize changes in latitudinal equitability gradients, functional diversity, palaeolatitudinal specialization, and community equitability. We identify: 1. global morphological communities becoming less specialized preceding the richness increase after the Cretaceous-Paleogene extinction; 2. Ecological specialization during the Early Eocene Climatic Optimum, suggesting inhibitive equatorial temperatures during the peak of the Cenozoic Hothouse; 3. Increased specialization due to circulation changes across the Eocene-Oligocene Transition, preceding the loss of morphological diversity; 4. Changes in morphological specialization and richness ~19 Ma, coeval with pelagic shark extinctions; 5. Delayed onset of changing functional group richness and specialization between hemispheres during the mid-Miocene plankton diversification. The detailed nature of the Triton dataset permits a unique spatiotemporal view of Cenozoic pelagic macroevolution, where global biogeographic responses of functional communities and richness are decoupled during Cenozoic climate events. Importantly, global response of functional groups to similar abiotic selection pressures may depend upon the background climatic state (Greenhouse/Icehouse) to which a group is adapted.