Cenozoic dynamics of shallow‐marine biodiversity in the Western Pacific

Abstract

Aim Cenozoic dynamics of large-scale species diversity patterns remain poorly understood, especially for the Western Pacific, in part, because of the paucity of well-dated fossil records from the tropics. This article aims to reveal the spatiotemporal dynamics of species diversity in the Western Pacific through the Cenozoic, focusing on the tropical Indo-Australian Archipelago (IAA) biodiversity hotspot.Location Tropical and north-western Pacific Ocean.Methods We analysed well-preserved fossil ostracodes from the tropical Western Pacific and combined their diversity data with other published data from the region to reconstruct Cenozoic dynamics of species diversity in the tropical and north-western Pacific Ocean. We fitted generalized additive models to test for differences in richness over time and across geographical regions while accounting for sample-size variation among samples.Results Low-, mid-and high-latitude regions all show a similar diversity trajectory: diversity is low in the Eocene and Oligocene, increases from the Early Miocene to the Plio-Pleistocene but then declines to the present day. Present-day high biodiversity in these regions was established during the Pliocene with a remarkable diversity increase at that time. Latitudinal diversity patterns are relatively flat and never show a simple decline from the tropics to higher latitudes.Main conclusions Western Pacific Cenozoic ostracodes exhibit a spatiotemporal pattern of species diversity that is inconsistent with the commonly reported and persistent pattern of declining diversity from the tropics to the extratropics. While this inconsistency could be interpreted as evidence that ostracodes are a contrarian clade, Atlantic ostracodes display a standard latitudinal species diversity gradient. Contrasting patterns between oceans suggest an important role for regional factors (e.g. plate tectonics and temporal geomorphological dynamics) in shaping the biodiversity of the Western Pacific.

Roles of climate niche conservatism and range dynamics in woody plant diversity patterns through the Cenozoic

“…However, we note substantial data limitations of tropical taxa, although tropical fossil sites accounted for 15% of all sampling sites across the globe (Supporting Information Appendix S2). Terrestrial woody genera showed relative undersampling at lower latitudes (Supporting Information Appendix S6), as observed in marine ecosystems (Jablonski et al, 2013;Yasuhara et al, 2017 including substantial fossils at low latitudes before the Neogene.…”

“…Such global-scale range dynamics of woody angiosperm genera suggest a contrast with latitudinal bridge taxa of marine organisms that dispersed from the tropics to higher latitudes. As a result of the presence of OTT bridge species, it is known that mid-and high-latitude marine diversity increased continuously throughout the Cenozoic (Buzas et al, 2002;Yasuhara et al, 2017).…”

Plate tectonic regulation of global marine animal diversity

“…Although biodiversity also appears to be in a declining phase (Fig. 2), it is not clear to what extent this decline reflects an actual downturn in biodiversity (22,49) versus idiosyncratic paleontological sampling of the tropics (39).…”

“…Without the end-Permian mass extinction, the Paleozoic biodiversity plateau (51) would likely have persisted until the start of the next fragmentation regime. Second, if coalescence does serve to stabilize biodiversity, then the increase in genus richness observed during the Cenozoic will likely slow or cease sometime in the relatively near future (22,49). A new interval of plate aggregation has been underway since the Late Cretaceous; this also suggests that any downturn in present-day taxonomic richness (52) may be followed by a protracted recovery phase that is more analogous to the Triassic than it is to the Paleogene, at least from the perspective of long-term plate tectonic boundary conditions.…”

Marine latitudinal diversity gradients, niche conservatism and out of the tropics and Arctic: Climatic sensitivity of small organisms

“…They are estimated to have >20,000 extant species that belong to a wide range of trophic groups, including deposit feeders, suspension feeders and scavengers (Horne et al, 2002;Rodriguez-Lazaro & Ruiz-Muñoz, 2012;Yasuhara & Cronin, 2008;Yasuhara, Tittensor, et al, 2017). Ostracods also have a fossil record that is comparable in richness to that of bivalves, as a result of their well-calcified carapaces, small size, high abundance and species-level identification achievable from fossilized carapaces (Holmes & Chivas, 2002;Huang et al, 2018;Yasuhara, Iwatani, et al, 2017;Yasuhara, Tittensor, et al, 2017). Thus, the factor preventing ostracods from becoming a better-established system to explore diversity dynamics is criterion a: the paucity of synthetic efforts to quantitatively document their large-scale biogeography, including their present-day LDGs.…”