| As an old endemic and ornamental plant in China, species Chimoncmthus praecox belongs to Chimonanthus Lindley of family Calycanthaceae. C. praecox is an allogamous and deciduous shrub with the entomophilous flowers bloom in winter. The species is diploid (2n=22) and its seeds are spread by gravity. C. praecox was widely distributed in southern China in the past, but now habitat fragmentation and human influence have caused significant reduction to this species. C. praecox is a useful material to study the impact of the glacial-interglacial climate changes during the Quaternary on species’evolution and distribution because the old species has experienced the climate fluctuations in Quaternary. Hence, the genetic conservation research is particularly important to the species.In this study, we used a popular SSR molecular marker(EST-SSR molecular marker) to discuss the genetic diversity and genetic structure on C. praecox. EST-SSR molecular markers can be obtained and developed directly from the free EST database. EST-SSR markers are a valuable tool to study the genetic diversity and genetic differentiation of intra-and interspecies. A total of867EST sequences of C. praecox were obtained from the NCBI database and75SSR information sites were detected among the867EST sequences. We designed31EST-SSR primers based on the SSR information sites. After examining the amplification with several C. praecox DNA,8polymorphic EST-SSR molecular markers were chose to study the species’genetic diversity and genetic structure at last.A neutral test was performed to test the EST-SSR markers for neutrality. All the8EST-SSR markers were suitable for the species evolutionary analysis using the neutral test.9C. praecox populations and one C. campanulatus R.H.Chang et C.S.Ding var. guizhouensis R.H.Chang population (200individuals in total) were collected to analyze the genetic diversity and genetic differentiation with8EST-SSR molecular markers in order to propose the conservation strategies. The main results were as follows:1. Both the9C. praecox populations and one C. campanulatus R.H.Chang et C.S.Ding var. guizhouensis R.H.Chang population accessed polymorphic alleles with the8EST-SSR markers, which indicated that the EST-SSR molecular markers developed from the EST sequences of C. praecox had good versatility. The analysis of genetic diversity revealed low genetic diversity among the species (PPL=55%, He=0.164,1=0.254).2. The result of F-statistics showed high genetic differentiation among C. praecox populations (FST=0.270). AMOVA analysis suggested that the main genetic variation of C. praecox happened among groups. The gene flow among the9C. praecox populations was not high (Nm=0.676), thus the genetic differentiation among populations emerged for the limited gene flow.3. Both the UPGMA cluster tree and the Bayesian clustering analysis illuminated a complex genetic structure and genetic differentiation among C. praecox populations. The Landscape Shape Interpolation analysis showed that the population structure of the species was closely related to the geographical distributions. The geographical isolations could weaken the gene flow among populations and caused genetic differentiation.4. Considering the genetic diversity and genetic structure of C. praecox, it was suggested to protect all the populations in situ. First of all, the habitat of all the populations should be protected. The gene flow among populations should be promoted in order to improve the genetic diversity of the species. If the ex situ conservation was implemented, enough individuals should be migrated to maintain the stability of population structure. |
PDF Full Text Request