• Search

About Us       Research       human resources       International Cooperation       News       Education & Training       Join Us       Journals       Publications       Resources       Contact
Location:Home > News > Events
Speciation Dynamics in the Himalayan–Hengduan Mountains: A Case from Parthenocissus, the Grape Family
Print  |  Close    Text size:A  A  A

The Tree of Life is not always bifurcated as we usually think, and sometimes gene flow between species makes the Tree of Life look more like a reticulate network, rather than a “tree”. Frequent hybridization can further cause two lineages to merge into one – if reproductive isolation is not established between the parents and the hybrids, the parents may be gradually replaced by their hybrid offspring, which eventually leads to speciation reversal.

In the Himalayan–Hengduan Mountains (HHM), frequent geological activities and climatic fluctuations have promoted hybridization events, and complex reticulate evolutionary histories of various lineages have been reported. However, no direct evidence of speciation reversal has been found, though some signals have been uncovered by previous studies.

In a study recently featured on the cover of New Phytologist (Fig. 1), Prof. CHEN Zhiduan's team from the Institute of Botany of the Chinese Academy of Sciences and international collaborators explored the speciation dynamics and mechanisms in the HHM in a robust spatial-temporal framework of reticulate evolution, with the trifoliolate lineage of Parthenocissus as an example.

The study restored the evolutionary history of multiple hybridization events of Parthenocissus with comprehensive approaches including phylogeny reconstruction, phylogenetic network inference, and gene flow detection, based on plastid and transcriptomic data. The biogeographic reconstruction showed diversification of the trifoliolate lineage beginning in the middle Oligocene, which coincides with the early establishment of the Hengduan Mountains.

With dense sampling of 212 individuals from 37 populations of the trifoliolate lineage, the researchers estimated the genetic admixture and spatial concentration of gene flow between populations. Three hybridization hot spots were identified, located on the southern slope of the Himalaya, the southern border of the Hengduan Mountains, and the southern edge of the HHM, respectively (Fig. 2).

At the third hybridization hot spot, the two co-existing species revealed an ongoing speciation reversal (Fig. 1). The two species previously persisted as distinct lineages for a long time, but the population structure indicated massive random hybridizations between them. And the pure parental lineages almost disappeared due to the “contamination” of genetic contributions from each other, suggesting a tendency of gradual replacement by widely distributed hybrid offspring.

Although speciation reversal is often recognized as a cause of biodiversity decline, hybrid lineages are important in the formation of biodiversity cradles. As a legacy of the parental lineages, the surviving genomic fractions in the gene pool continuously help the extant species adapt to the changing environment. And under certain circumstances, the hybrid lineages can diverge into different lineages again. Therefore, the researchers suggest that the conservation of hybrid populations and their habitats should be promoted to maintain the potential of generating future biodiversity, as global climate change is well underway.

Fig. 1 Cover Legend of volume 238, issue 2: Illustration representing reticulate evolution among four species of Parthenocissus in the Himalayan–Hengduan Mountains with twining tendrils indicating gene flow. Image courtesy of Aili Li and Limin Lu (Yu et al., pp. 888–903).

Fig. 2 Population structure and geographic distribution of species in the trifoliolate lineage of Parthenocissus, with red dashed lines indicating three hybridization hot spots in the Himalayan–Hengduan Mountains.

Article Link: https://doi.org/10.1111/nph.18580


LU Limin, CHEN Zhiduan
Institute of Botany, the Chinese Academy of Sciences
Email: liminlu@ibcas.ac.cn,

Institute of Botany, CAS    Add: No.20 Nanxincun, Xiangshan, Beijing 100093, China
京ICP备16067583号-24 Tel: +86 10 6283 6215    Fax: +86 10 6259 0833    E-mail: Int_Office@ibcas.ac.cn