Cenozoic evolution of beta diversity and a Pleistocene emergence for modern mammal faunas in China

Abstract

Aim Historical changes in community structure underlie modern spatial diversity patterns, but few empirical studies have focused on the variation in the community composition of fossil assemblages at large spatio‐temporal scales. We investigated how the spatial differentiation of mammal communities changed in China throughout the Cenozoic in response to tectonic uplift and palaeoclimatic changes and explore the timing of the emergence of the modern spatially structured faunas. Location China. Time period Cenozoic (from 65 Ma to the present). Major taxa studied Terrestrial mammals. Methods We used a compiled database of the distributions of fossils and extant mammals to compare the multiple‐site beta diversity among families and genera within six time intervals of the Cenozoic using Sørensen dissimilarity (βsor) and Simpson dissimilarity (βsim). To investigate the timing of the emergence of the modern spatially structured faunas, we applied hierarchical clustering and non‐metric multidimensional scaling ordination based on pairwise βsim among seven zoogeographical regions for each time slice. Results The multiple‐site beta diversity at the family level displayed hump‐shaped changes during the Cenozoic, and it peaked in the Eocene and gradually decreased towards the present. However, the genus‐level multiple‐site beta diversity remained rather constant throughout the Cenozoic. Pronounced variations in the relationships among the zoogeographical regions were revealed in both the cluster analyses and the ordinations. The modern spatial structure of mammal faunas at the family level was broadly similar to those observed in the Pliocene and Pleistocene. Main conclusions The spatial differentiation of mammal faunas in China dates back to the Eocene and pre‐dates the formation of modern topography and climate. Throughout the Cenozoic, the spatial structure of mammal faunas was reorganized by an interplay of the uplift of the Tibetan Plateau, the emergence of the monsoon system and global macroevolutionary processes. The modern relationships among zoogeographical regions at the family level were established in the Pleistocene.

Evolutionary history of zoogeographical regions surrounding the Tibetan Plateau

“…4 ), the correlation between their β sim dissimilarity matrices remained significant (Mantel test, P < 0.05; Supplementary Table 1 ). Previous palaeontological analyses in China yielded a similar timing and showed that the spatial structure of mammalian communities originated during the Pliocene 9 , 51 . This probably happened because the emergence of modern orographic patterns 52 and monsoon systems 4 has formed dispersal limitations and accelerated lineage diversification.…”

“…We standardised the taxonomy according to the Paleobiology Database and excluded taxa unidentifiable at the genus level. We removed the duplicated records and merged spatially closest collection localities by combining those within 0.1 latitude and longitude 9 . Our final fossil dataset consisted of 5880 fossil occurrences of 170 families and 1278 genera (Supplementary Data 2 ).…”

“…There is growing evidence that the present-day zoogeographical regions surrounding the TP are the products of geological processes and past climatic changes 7 – 9 . A common hypothesis is that the TP uplift created species-dispersal barriers during the Cenozoic 10 , 11 , and subsequent climatic changes in Asia increased environmental heterogeneity (Fig.…”

“…To date, two primary analyses of community-level data have been used to reconstruct the evolutionary history of zoogeographical regions. One tracked temporal changes in beta diversity between extant communities over a phylogenetic timescale 23 , 24 , and another compared compositional dissimilarities among fossil assemblages over geological time 9 , 25 . However, both methods have their pros and cons 26 .…”

Spatial scaling of beta diversity in the shallow-marine fossil record

“…Previous studies of beta diversity in the fossil record at large spatiotemporal scales have allowed for spatial variability in sampling by combining collections based on either a grid system (Crampton et al 2011; Brocklehurst et al 2018; Penny and Kröger 2019) or a specified distance (He et al 2018). However, these approaches do not necessarily account for temporal variation in spatial distribution or area, and time series of beta diversity may be affected by this.…”