Phylogeography of East Asia’s Tertiary relict plants: current progress and future prospects

Abstract

In this review, based on recent studies of population genetics and phylogeographics of East Asia's Tertiary relict plants, we have outlined the main phylogeographic patterns and processes. We also summarize common geographic and environmental factors which may contribute to the phylogeographic patterns of East Asia's Tertiary relict plants and present future challenges and research prospects. There are four recurrent phylogeographic scenarios identified by different case studies, including: (1) the global cooling and aridification during the Middle and Late Miocene induced recent speciation, with climate change during the Late Pliocene and Pleistocene accounting for their intra-specific lineage divergence, genetic diversification and demographic expansion/contraction. The latitudinal contraction/expansion can lead to the formation of "suture zone" for some relict plants; (2) the effects of the formation of the glacial East China Sea land bridge, as a "corridor" or "filter", have to account not only for habitat preferences per se but also for other biological features of different relict plant species; (3) the uplift of the Qinghai-Tibet Plateau (QTP) during the Late Pliocene and the intensification of East Asian monsoon system (EAMS) are the most suggestive factors responsible for the major phylogeographic break between the western and eastern lineages across the Sichuan Basin and northwestern arid regions; and (4) some Tertiary relict plants migrated southward to Taiwan from mainland China or Japan before the Pleistocene under global climatic cooling and aridification since the Late