Tectonic and climatic impacts on the biota within the Red River Fault, evidence from phylogeography of Cycas dolichophylla (Cycadaceae)

Abstract

Dramatic crustal deformation and river incision in Southwest China induced by the Indo-Asian collision have long been argued to contribute to the complicated landscapes, heterogeneous environment and abundant biodiversity in this region. However, biological impacts in promoting intraspecific phylogeographical subdivision and divergence along the Red River Fault zone (RRF) remain poorly understood. To investigate the possible biological effects of tectonic movements and environment variations within the RRF, the phylogeography of Cycas dolichophylla-an endemic but widely distributed Cycas in Southwest China and North Vietnam along the RRF were carried out based on four chloroplast DNA intergenic spacers (cpDNA), three nuclear DNA sequences (nDNA) and 16 simple sequence repeat variations (SSR). Two different phylogeographical patterns were detected: a Southwest-Northeast break across the RRF disclosed by chlorotypes and a China-Vietnam separation revealed by SSR. A Bayesian skyline plot from cpDNA data demonstrated a historical increasing, but a recent declining, dynamic in population size during the Pleistocene. Consequently, we infer it is the local environmental variation during Cenozoic that contributed to the complex landscape and microclimate mosaics, facilitating speciation and divergence of C. dolichophylla. Subsequently, the Quaternary climatic fluctuations coupled with human activities profoundly influenced the genetic structure and demographic history of this species.

Population Differentiation and Demographic History of the Cycas taiwaniana Complex (Cycadaceae) Endemic to South China as Indicated by DNA Sequences and Microsatellite Markers

“…The divergence time of the two lineages based on cpDNA and SCNG sequences is about 1.790 and 0.311 Ma, respectively, corresponding to a period of glacial cycle during the Middle Pleistocene, which verifies recent divergence in the former research (Nagalingum et al, 2011). The divergence time from cpDNA and SCNG was inconsistent, which is caused by different evolutionary rates and migration modes between organelle (pollen migration) and nuclear markers (pollen migration and seed migration; seed migration is very little) (Wolfe et al, 1987;Zheng et al, 2016). The recent divergence between the two lineages indicated that the species in clade B colonized Hainan Island in the Middle Pleistocene when land bridges formed (Shi et al, 2006;Huang et al, 2013b).…”

The distribution, diversity, and conservation status of Cycas in China

“…Based on Bayesian Skyline Plot, a scenario of population expansion was suggested for both C. revoluta and C. taitungensis (Chiang et al., ), which contrary to the contraction experience occurred on southeast Asia Cycas species (Feng, Zheng, & Gong, ; Feng, Liu, et al., ; Gong et al., ; Zheng et al., ). One possible reason for this contrast is the different evolutionary processes of both topography and species in history (Gong et al., ; Huang et al., ; Kizaki & Oshiro, ; Shaw & Huang, ).…”

“…Most cycads live in valleys or monsoon forests on low-altitude slopes of ridges and cliffs (Fragnière et al, 2015), where is characterized by warm and moist conditions. However, the glacial-interglacial cycles, accompanied by a strengthened Asian winter monsoon dominating over continental southeast Asia (Cook & Jones, 2012), restricted Cycas into scattered habitats and hindered gene flow between populations (Feng et al, 2014;Liu et al, 2015;Xie, Jian, & Liu, 2005;Zhan et al, 2011;Zheng et al, 2016). Consequently, small populations were gradually isolated, which profoundly influenced the current demography, genetic structure, and population size.…”

“…As a recently radiated lineage, some Cycas species in southwest China exhibit high genetic diversity at the species level, low genetic diversity within populations, and significant genetic differentiation among populations (Feng, Wang, & Gong, ; Gong et al., ; Liu, Zhou, & Gong, ; Zheng, Liu, & Gong, ). However, specific comparison concerning genetic variations of all the Cycas species in China has rarely been performed.…”

“…As a recently radiated lineage, some Cycas species in southwest China exhibit high genetic diversity at the species level, low genetic diversity within populations, and significant genetic differentiation among populations (Feng, Wang, & Gong, 2014;Gong et al, 2015;Liu, Zhou, & Gong, 2015;Zheng, Liu, & Gong, 2016 (Ma et al, 2013), displaying the highest proportion of the genus than any other plant groups (15/23, 65%) (Sun, 2013;Zheng et al, 2013). As human disturbance has severely disturbed Cycas populations and its habitats, multiple protective efforts have been made over the last decade (Luo, Tang, Huang, Liang, & Zhao, 2014;Zhan, Wang, Gong, & Peng, 2011).…”