Comparative phylogeography study reveals introgression and incomplete lineage sorting during rapid diversification of
Jianling You1,2, Stephen C Lougheed3, Yao Zhao4
1The Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Institute of Botany, Tibet University-Fudan University Joint Laboratory for Biodiversity and Global Change, Fudan University, Shanghai, China.
Rapid plant radiation in the Qinghai-Tibetan Plateau (QTP) and Hengduan Mountains (HM) involved introgressive hybridization and incomplete lineage sorting. These processes, alongside geographic isolation, shaped phylogeographic patterns in Rhodiola species.
Area of Science:
- Evolutionary biology
- Phylogeography
- Plant speciation
Background:
- The Qinghai-Tibetan Plateau (QTP) and Hengduan Mountains (HM) are biodiversity hotspots with rapid Quaternary plant radiation.
- Frequent secondary contact between diverging plant populations complicates understanding of their evolutionary history.
- The roles of incomplete lineage sorting and introgressive hybridization in phylogeography remain underdetermined.
Purpose of the Study:
- To investigate phylogeographic patterns in four Rhodiola species from the QTP and HM.
- To compare evolutionary histories, geographic ranges, and reproductive modes influencing diversification.
- To determine the impact of introgressive hybridization and incomplete lineage sorting on rapid radiation.
Main Methods:
- Analysis of chloroplast DNA (cpDNA) and internal transcribed spacer (ITS) sequence variations.
- Sampling of 611 individuals across four Rhodiola species: R. bupleuroides, R. discolor, R. fastigiata, and R. chrysanthemifolia.
- Comparison of phylogeographic patterns considering species-specific traits.
Main Results:
- Divergence times align with peak in situ speciation in the HM during the Quaternary.
- Shared ribotypes and haplotypes in sympatric populations suggest introgressive hybridization.
- Phylogenetic discordance between ribotypes and haplotypes indicates incomplete lineage sorting in three species.
- Rhodiola discolor exhibits exceptional cpDNA haplotype richness, potentially due to adaptive radiation.
Conclusions:
- Geographic isolation and climate oscillations are key drivers of Quaternary diversification.
- Introgressive hybridization and incomplete lineage sorting significantly contribute to rapid diversification in the QTP and HM.
- These evolutionary mechanisms provide a comprehensive explanation for the phylogeographic complexity observed in the studied Rhodiola species.
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