Multilocus analysis of genetic variation and speciation model in Miscanthus (Poaceae)

• Main Authors: Chuan-WenHo, 何瓊紋
• Other Authors: Tzen-Yuh Chiang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/48865124722941366680

博士 === 國立成功大學 === 生命科學系碩博士班 === 101 === Miscanthus, is one of the most important biofuel plants with characteristics of fast growth and high biomass. M. sinensis/floridulus are composed of morphologically distinct intraspecific taxa that are distributed along an altitudinal gradient and respond to various environmental stresses. This species complex which diverged only recently can provide insight into the formation of new species and local adaptation. In this study, 80 DNA markers were developed based on newly assembled transcriptome data, and were used to explore the divergence in Miscanthus floridulus/sinensis species complex. In the standard model of allopatric speciation, the ancestral population was split into two geographically regional populations with no subsequent gene flow. In the study, multi-locus population genetic analyses revealed frequent gene flow both between species and among intraspecific taxa of M. sinensis. Furthermore, none of the nuclear loci supported the species phylogeny. Statistical analyses showed that such systematic inconsistency cannot be explained solely by the ancestral polymorphisms, while was caused by gene flow after speciation. Nevertheless, phylogenetic simulations via allele resampling were able to uncover the identity of species and intraspecific taxa, suggesting that there must exist some extrinsic cohesive forces counteracting the genetic exchanges between species. Compared to neutral background loci that were likely mediated with gene flow, outlier loci of a small proportion of the loci selected (3.75－15.0%) differentiated Miscanthus species/ races, and displayed higher linkage disequilibrium between SNP sites, agreeing with a model of parapatric speciation. The speciation of Miscanthus, was likely triggered by diversifying selection at few outlier loci, followed by widening divergence hitchhiking along chromosomes.