In evolutionary biology, the study of living species and fossils are usually independent of each other. It is worth noting that an integration of the evolutionary dynamics and succession of fossils with the historical biogeography and phylogenetic reconstruction of extant species will offer a bridge in understanding ancient and recent evolution, allowing more accurate reconstruction of the evolutionary history of organisms.
The abundance of fossils and extant species rank the glires as ideal candidates to study on their historical evolution at a global level as well as the influence of geological or climate events acted on the speciation, morphological evolution and geographical diversification of these animals. The research group of Mammalogy of the Institute of Zoology, Chinese Academy of Sciences, and their cooperators, recently made new progress in revealing the main events that might have driven the evolutionary trajectories of the representative groups of glires. They integrated the information from fossils with DNA markers, morphological characters and distribution range of extant species. These studies shed light on the main causes that might induce the evolutionary process of different herbivores: The uplift of plateaus, the formation of monsoon climate, as well as the sea level eustacy induced by glacial climate, which droved global vegetation change, and then triggered the evolutionary dynamics of different groups.
Dipodoidea is a diverse rodent group and its earliest-known fossil record is from Eocene. Each of the three ecological groups of the extant Dipodoidea (sicistines, zapodines, and jerboas) has its distinctive phylogenetic construction and geographical distribution. These distribution patterns have been shaped by the dispersal events. The key events of paleogeographic distribution coincided with the major paleoenvironmental events in the Cenozoic. The first important diversification phase occurred during Oligocene to Early Miocene, when the global climate underwent prominent change since the boundary of Eocene/Oligocene. The second adaptive radiation occurred within jerboas, which was associated with expansion of open habitat since late Middle Miocene. Habitat change responding to global and regional climatic events has greatly advanced the diversification of jerboas.
Flying squirrels (Rodentia: Sciuridae: Pteromyini) are strictly arboreal squirrels adopting a special gliding locomotion. Recently, the worldwide fossil occurrences of Pteromyini were reviewed. The origin center and evolutionary process of these animals were deduced from fossil records and the Dispersal-Vicariance Analysis of extant species. Results showed that flying squirrels probably originated in the Oligocene-Miocene transition from Europe and immediately dispersed to Asia and North America. Then influenced by the glaciation, CO2 reduction, orogenic movements and Paratethys retreat, the Northern Hemisphere underwent a course of climate deterioration and grassland expansion during the late Miocene, and the diversity of flying squirrels dramatically decreased. The uplift of Tibet Plateau plus the strengthened Asian monsoons intensified the aridity in central Asia but brought sufficient water to the densely forested South and Southeast Asia. These forests were supposed to be the refuges and diversification center for flying squirrels during the transition from Tertiary to Quarternary and the glacial period.
Although species within Lagomorpha are derived from a common ancestor, the distribution range and body size of its two extant groups, ochotonids and leporids, are quite differentiated. Within ochotonids, more than 20 genera occupied the period from the early Miocene to middle Miocene, whereas most of them became extinct during the transition from the Miocene to Pliocene. The peak diversity of the leporids occurred during the Miocene to Pliocene transition, while their diversity dramatically decreased in the late Quaternary. The forage selection of extant pikas features a strong preference for C3 plants, while for the diet of leporids, more than 16% of plant species were identified as C4 (31% species are from Poaceae). The ability of several leporid species to consume C4 plants is likely to result in their size increase and range expansion, most notably in Lepus. E xpansion of C4 plants in the late Miocene, the so called ‘nature’s green revolution’, induced by global environmental change , was suggested to be one of the major ’ecological opportunities’, which probably drove large scale extinction and range contraction of ochotonids, but inversely promoted diversification and range expansion of leporids.
These studies were mainly completed by the following institutes: Institute of Zoology, Institute of Vertebrate Paleontology and Paleoanthropology and Kunming Institute of Zoology from the Chinese Academy of Sciences and Geological Institute, Siberian Branch, Russian Academy of Sciences. Main publications related to these studies are given as followings:
Ge Deyan, Wen Zhixin, Xia Lin, Zhang Zhaoqun, Erbajeva Margarita, Huang Chengming, Yang Qisen*. 2013. Evolutionary History of Lagomorphs in Response to Global Environmental Change. PLoS ONE. 8(4): e59668. doi: 10.1371/journal. pone.0059668.
LV Xuefei, Ge Deyan, Xia Lin, Zhang Zhaoqun, Song Li, Yang Qisen*. 2013. The evolution and paleobiogeography of fly squirrels (Sciuridae: Pteromyini) in response to global environmental change. Evolutionary Biology, 40(1):117-132. doi:10.1007/s11692-012-9191-6.
Zhang Qian, Xia Lin, Yuri Kimura, Georgy Shenbrot, Zhang Zhaoqun, Ge Deyan, Yang Qisen*. 2013. Tracing the origin and diversification of Dipodoidea (Order: Rodentia): Evidence from fossil record and molecular phylogeny. Evolutionary Biology, 40(1):32-44. doi:10.1007/s11692-012-9167-6.
Ge Deyan, Zhang Zhaoqun, Xia Lin, Zhang Qian, Ma Yong, Yang Qisen*. 2012. Did the expansion of C-4 plants drive extinction and massive range contraction of micromammals? Inferences from food preference and historical biogeography of pikas. Palaeogeography, Palaeoclimatology, Palaeoecology, 326:160-171. doi: 10.1016/j.palaeo.2012.02.016.
