Molecular Identification Of Natural Hybridization In Melastoma In Sabah And Sarawa Of Malaysia

Melastoma(Melastomataceae)is mainly distributed from southern.Asia to the north of Oceania,and its many species and varieties have excellent ornamental and medicinal properties.This genus has experienced rapid adaptive radiation and formed about 80-90 species in the past one million years.Of these species,41 are distributed in Borneo.Natural hybridization palys an important role in speciation and diversification of Melastoma.Southeast Asia is the distribution center of Melastoma,but it remains unclear if natural hyrbidization is an important mechasnism for the formation of species diversity of Melastoma in Southeast Asia.In this study,we collected three putative cases of natural hybridization from Malaysian Borneo.Of which,one was collected from Crocker Range,includes an unidentified species(Rc),Melastoma beccarianum(Bc)and a putative hybrid(BRc)between them;one was collected from Mesilau,including an unidentified species(Rk),Melastoma boryanum(Bk)and the putative hybrid(BRk)between them;and another was collected from Lambir Hills National Park,Miri,containing M.beccarianum(Bm),Melastoma malabatricum(Mm)and a putative hybrid(BMm)between them.We sequenced three nuclear genes and one chloroplast intergenic spacer to determine the species status of an unidentified taxon,assess patterns of genetic diversity of two species with multiple populations,and test the three hybridization events.Main results and conclusions of this study are as follows:1)The unidentified taxon with high morphological similarity to M.malabathricum was resolved as a variety of M.malabathricum,and named as Melastoma malabathricum var.tomentosum.2)The four populations of M.malabathricum all have high level of genetic diversity,M.malabathricum var.tomentosum have a modest level of genetic differentiation with M.malabathricum.The two populations of M.beccarianum also have high level of both genetic diversity and genetic differentiation,especially at the vr gene,no haplotype was shared between them.3)All the three cases of natural hybridization were verified and introgressive occurred between each pair of parental species.Our study suggests that natural hyrbidization is an important mechanism for the formation of species diversity of Melastoma in Southeast Asia.Introgression between different species of Melastoma may facilitate the transfre of adaptive traits.Meanwhile,Habitat disturbance from human acativities in the recent years may incur the increasing rate of hybridization.Hybridization between the widespread species M.malabathricum and each of the locally endemic species,M.beccarianum and M.boryanum,can waste the reproductive energe and thus population contraction.This will raise the issue of conservation biology in Melastoma.Therefore,our study is also of theoretical and practical sigificance in preserving germplasm resources of Melastoma.