Abstract Detail


Li, Ning [1], Su, Yingjuan [1], Wang, Ting [2].

Effects of climatic fluctuations and restricted gene flow on the fragmented distribution pattern of Tertiary relict conifer Pseudotaxus chienii (Taxaceae) revealed by chloroplast and nuclear markers.

Pseudotaxus chienii, a Tertiary relict conifer, is endemic to subtropical China with a fragmented distribution pattern. Habitat fragmentation can facilitate local adaptation of species to heterogeneous environments by affecting population demographic history. To investigate the factors affecting the evolutionary dynamics, such as climatic fluctuations and complex geomorphological features, this study used a phylogeographic analysis to clarify the formation mechanism of the fragmented distribution pattern of P. chienii. In this study, based on extensive range-wide sampling, we employed twelve chloroplast microsatellites (cpSSR), fifteen nuclear microsatellites (nSSR), three chloroplast regions (cpDNA: trnL-trnF, trnD-trnT, and psbC-trnS), and two nuclear regions (ITS and NEEDLY3) to verify the genetic structure and phylogeographic history of P. chienii. Furthermore, the current and past distributions of P. chienii were constructed by conducting the ecological niche modelling. Medium to high levels of genetic diversities (cpSSR: UHe = 0.167; nSSR: UHe = 0.541; cpDNA: hd = 0.751; ITS: hd = 0.855; NEEDLY3: hd = 0.695) were found at the species level, which might be caused by the accumulation of genetic variation in long-lived conifer with long evolutionary time. According to approximate Bayesian computation, the group A composed of Zhejiang and Jiangxi populations and group B composed of Hunan population diverged from their common ancestor in late Miocene, which might be influenced by the strengthening process of East Asian monsoon at 8 Ma. The group C composed of Guangxi populations subsequently diverged from group A in early Pleistocene, which coincided with the Quaternary glacial-interglacial cycles. Soon afterwards, the ecological niche modelling showed that P. chienii was limited to multiple localized refugial areas and experienced habitat fragmentation during the Last Glacial Maximum, and post-glacial local range expansions were supported by mismatch distribution analysis. Meanwhile, a significant phylogeographic structure was detected (NST > GST, P < 0.05) and affected by fragmented distribution, and BARRIER analyses divided all populations into three different genetic groups with restricted gene flow (all Nm < 1), which were separated by Nanling Mountains and Luoxiao Mountains. The restricted gene flow could be attributed to the limited dispersal of pollen and seed influenced by understory habitats and complicated geomorphological features in subtropical China, both of which might act as physical barriers to gene flow. In addition, local adaptation to heterogeneous environments also contributed to maintain the fragmented distribution. Finally, incomplete lineage sorting or introgression can lead to the cytonuclear discordance. Overall, this study suggests that pre-Quaternary and Quaternary climatic fluctuations and restricted gene flow have significant effects on the formation and maintenance of fragmented distribution pattern of P. chienii. Meanwhile, it provides deep insights into the evolutionary history of plants in subtropical China.

1 - Sun Yat-Sen University
2 - South China Agricultural University

Pseudotaxus chienii
ecological niche modelling
climatic fluctuations
gene flow
fragmented distribution pattern.

Presentation Type: Oral Paper
Number: BIOG I006
Abstract ID:277
Candidate for Awards:None

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