Studies have revealed changes in Asian rodent populations and their response to environmental change

Combination of East Asian rodents from the Early Eocene to the Early Oligocene. (Photo courtesy of Vertebrate Paleontology and Paleontology, Chinese Academy of Sciences)

Changes in the diversity of the East Asian rodent genera from the Early Eocene to the Early Oligocene. (Photo courtesy of Vertebrate Paleontology and Paleontology, Chinese Academy of Sciences)

Rodents originated in Asia and are a very important taxa of Cenozoic land mammals, successfully crossing the global cooling event at the turn of the Eocene/Oligocene to become the dominant group of Mammals in East Asia. The origin, evolution, and succession of rodents in fauna has been closely linked to global climate change since the Cenozoic Era. However, there has long been a lack of exploration of the relationship between the succession of rodent groups and paleoenvironmental changes, and little is known about how these animals adapted to and responded to global climate upheavals in the early Oligocene.

Recently, Li Qian et al., institute of vertebrate paleontology and paleoanthropology of the Chinese Academy of Sciences, comprehensively sorted out the fossil data of Asian rodents from the early Eocene to the Early Oligocene, and deeply explored the characteristics of rodent groups in different periods under the framework of Asian mammal staging, and analyzed the diversity of rodents at the genus level, which was published in Frontiers of Ecology and Evolution.

The results of the study showed that rodent groups from the Early Ephemerocene to the Early Oligocene were more continuous in East Asia (including China and Mongolia), and the rodent fossil records in Central Asia (Kazakhstan and Kyrgyzstan) and South Asia (mainly India, Pakistan, Thailand and Myanmar) were incomplete.

Rodent groups in South Asia, although recorded discontinuously, present a unique combination of appearances, and differences in appearances with contemporaneous rodent groups in East and Central Asia are likely to be caused by different habitats. Some species in the South Asian rodent population show closer affinity with rodents in Africa.

The rodent populations of East Asia showed obvious replacement with the changes of paleoclimate, and their diversity was corrected by sparse standardization method, showing that rodents in the collapse period of the early Eocene had shown moderate diversity; The continued increase in rodent diversity during the Middle Eocene Ildinmanha and Salamulun periods is likely to be related to the “Moderate Climate Period of the Middle Eocene”; The global temperature gradually decreased after the suitable period, the diversity of rodents showed a significant decrease, and the dominant taxa in the rodent group changed from comb-toed rats to hamsters and jerboas. At the turn of the Eocene/Oligocene, the world cooled down, but east Asian rodents showed an increase in diversity, while hamsters and jerbourines remained dominant in rodent groups.

It can be seen that the low temperature environment from the Late Eocene to the Late Eocene in East Asia is likely to have created a training ground for hamsters and jerbourines, allowing these taxa to have some pre-adaptation, so that rodents not only successfully survived the global cooling event at the turn of the Eocene/Oligocene, but also became one of the dominant taxa in the Oligocene East Asian mammal group.

The research of this project has been co-funded by the Strategic Pilot Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China. (Source: China Science Daily Cui Xueqin)

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