Cenozoic dynamics of shallow marine biodiversity

Abstract

The Cenozoic is the third of the major eras of Earth’s history, during which flora and fauna evolved toward those of the present. Examination of a Cenozoic history of marine biodiversity is essential for us to understand the interaction of biotic/intrinsic and abiotic/extrinsic factors in driving macroevolution and underpinning modern biodiversity and biogeographic patterns since the deep past. In an integrated spatial and temporal framework, I focused on two intervals within the Cenozoic, namely the Paleocene-Eocene Thermal Maximum (PETM) as a transient geological state of abrupt and extreme perturbations in the carbon cycle, climate, and ocean chemistry, and the Neogene Period as a mean geological state of gradual and slow-evolving transition from the Coolhouse to Icehouse states. Using fossil ostracods as a model system, my studies revealed that shallow-marine ecosystems responded to long-term and short-term changes in paleoenvironments in markedly dynamic ways. During the PETM, increased thermal and oxygen pressure triggered a strong collapse-recovery pattern of shallow-marine biodiversity by extinctions and bathymetrical migrations. Throughout the Neogene, a tropical hotspot of unproportionally high diversity developed in the Indo-Australian Archipelago (IAA) driven by diversity dependency, cooling climates and extensive suitable habitats. Over very different temporal scales of these two studies, noticeably, temperature was indicated as the most important abiotic controller of marine diversity dynamics that elevated warmth in greenhouse climates inhibited speciation while enhanced extinction. A historical perspective therefore not only unveils the evolutionary origins of modern-day biodiversity but also implies its fate under future scenarios of anthropogenic warming, as a large number of species may be lost with the fundamental biological character of Earth’s oceans permanently altered.