Vegetation diversity and distribution in the Pliocene of the southern Hengduan Mountains region

Abstract

Aims: Due to complex geomorphology and diverse landscapes, the southern Hengduan Mountains region is home to highly diverse vegetation. The evolution and formation of such diversity is an interesting topic in the fields of botany and ecology, and plant fossils are an important proxy for researching this question. Method: In this study, we integrated published sources of nine fossil floras from the Pliocene of the southern Hengduan Mountains region. We first inferred the vegetation types of these fossil floras on the basis of their taxonomic compositions and dominant elements, and then depicted the diversity and spatial distribution of vegetation in the regionduring the Pliocene. We also correlated the rise of vegetation diversity and the formation of vegetation distribution to major environmental changes in the southern Hengduan Mountains region. Results: Our synthesis indicates that the southern Hengduan Mountain region already held a variety of vegetation types during the Pliocene, including subtropical evergreen broadleaved forest, subtropical deciduous broadleaved forest, sclerophyllous evergreen broadleaved forest, mixed coniferous broadleaved forest and shrubby meadow. The vegetation tended to have a warm affinity in the south and a cool-temperate affinity in the north, demonstrating altitudinal gradients with latitude at that time. Moreover, vegetation types are shown to be stratified at some localities, suggesting altitudinal gradients at local scales that are likely associated with the occurrence of high mountains. These are highly similar to the modern patterns of vegetation diversity and distribution in this region. Conclusion:Our study concludes that the modern diversity and distribution of vegetation in the southern Hengduan Mountain region was established no later than the Pliocene. However, more plant fossils from deeper times are needed to verify if the current vegetation was formed at an earlier geological age.

The emergence of modern zoogeographic regions in Asia examined through climate–dental trait association patterns

“…The low temperatures to which such mammalian communities point is consistent with the appearance of an altitudinal vegetation zonation 46 – 48 and the absence of previously prevailing middle-sized hominids in this area during the Pliocene 49 . Today’s Hengduan Mountains are identified as a montane forest biodiversity hotspot 6 , our results support the emergence of this hotspot during the Pliocene 50 . In the Pliocene, the fossil communities of the Tibetan Plateau are characterized by species endemic to the central Plateau 51 , on one hand, and snow-adapted Zanda fauna in the southern Plateau 52 , 53 , on the other hand, indicating that Alpine fauna had already established on the Tibetan Plateau.…”

A new Rattus species and its associated micromammals from the Pliocene Yangyi Formation in Baoshan, western Yunnan, China

“…According to the previous analysis of plant megafossil and sporopollen fossils, the paleoclimate of the western region in Yunnan from the Paleocene to the Late Miocene, as a whole, was relatively stable and it was in the warm and humid subtropical monsoon area until the Late Pliocene (Huang et al, 2016;Xie et al, 2019). In the Late Pliocene, the Baoshan area appeared the vertical zonation of vegetation similar to today, and the paleoclimate is not significantly different from the present (Huang et al, 2022;Sun et al, 2011). This transformation in flora may have been influenced by both global climatic changes and the uplift of the Tibetan Plateau (Kou et al, 2006;Sun et al, 2011;Xie et al, 2019).…”