Speciation And Evolutionary History Of The Genus Notopterygium

Historical geo-climatic events have shaped the distributional patterns and interspecific divergence of plants.In the past few years,the numerous population genetics studies in China have focused on the Qinghai-Tibetan Plateau?QTP?and surrounding areas due to its complex topography and high species diversity,but the speciation and spatiotemporal population dynamics of cold-tolerant herbal species in the QTP and adjacent areas remains poorly understood.In this study,we analyzed the genetic structure,population differentiation and evolutionary history of these four endangered medicinal Notopterygium herbs?N.incisum,N.franchetii,N.oviforme and N.forrestii?in the QTP and adjacent areas.We sequenced one chloroplast DNA regions?OG28079?,two mitochondrial DNA regions?OG537,OG917?and10 nuclear loci?35,9122,25629,25679,29206,32125,51964,OG29101,OG29960,OG29988?in 340 individuals sampled from 72 natural populations of these four species.Sequenced these samples,and combined with the species' distribution modeling test the formation history and population differentiation.The results show that:?1?As for the four Notopterygium species,the silent nucleotide diversity(?_sil)of N.oviforme?0.0055?was higher than N.franchetii?0.0050?,N.incisum?0.0036?and N.forrestii?0.0029?.?2?Phylogenetic analysis based on nuclear markers suggested that there were obvious genetic divergence in the four Notopterygium species,N.incisum formed a monophyletic clade with high bootstrap support,where N.franchetii and N.oviforme showed a close genetic relationship.?3?The effective population size of four species was larger than that of their ancestral population sizes,suggested that these species may had exhibited obvious demographic expansions.The Isolation with Migration?IM?analyses suggested that the divergence between these four Notopterygium species occurred had approximately between1.74 to 6.32 Mya,it was significantly associated with recent extensive uplifts of the QTP.?4?Species distribution modeling and population genetics analysis showed that N.incisum and N.franchetii exhibited obvious demographic expansions during the Last glacial maximum?LGM?,but N.oviforme had occurred demographic contraction.These findings point to the importance roles of geological and climatic changes during the Pliocene and Pleistocene as causes of intraspecific diversification and interspecific differentiation of cold-tolerant herbal species in the QTP biodiversity hot spot region.