Study On The Genetic Relationship And Habitat Distribution Of The Pleione

The genus Pleione belongs to the Orchidaceae family,with about 37 species in the whole genus.The genus is a perennial and endangered herb.Pleione plants not only have high ornamental properties,but also have certain medicinal value.Among them,Pleione bulbocodioides and Pleione yunnanensis,commonly known as"ice-ball",are the base plants of the precious medicinal material"shan-ci-gu",which have the effect of clearing away heat and detoxifying,eliminating carbuncle and unbinding.The weak reproductive isolation and easy hybridization of Pleione led to small differences in morphological characteristics and tissue structure among species,which led to unclear interspecific relationships.It is of great significance to analyze the interspecific relationship of this genus and evaluate its suitability distribution under climate change for the conservation and utilization of this genus.First,this study used ITS sequences and SCo T molecular markers to assess the genetic relationship and genetic diversity of Pleione species;Secondly,the phylogenetic relationship of the genus was analyzed based on chloroplast genome information;Finally,the Maxent and Arc GIS models combined with climate and terrain variables were used to research the suitable habitat areas of Pleione bulbocodioides and Pleione yunnanensis under different climate scenarios at present and in the future.The results of the study are as follows:(1)Interspecific relationships and genetic diversity of 16 individuals from 11species of Pleione were evaluated using ITS and SCo T markers.A total of 84 bands were obtained from 11 SCo T primers with an average of 7.6 bands per primer,of which 83 were polymorphic bands with a polymorphism ratio of 99%;the genetic distances of different species of Pleione were 0.005-0.271,the variation range of genetic similarity coefficients among different individuals was 0.4524-0.9048;the effective number of alleles(Ne),Shannon’s information index(I)and Nei genetic diversity(H)in the total population were 1.54,0.49 and 0.33,respectively.The present result demonstrates that the genetic relationship of Pleione species can be analyzed by ITS sequence and the SCo T marker can be used for the genetic variation analysis of Pleione due to its good versatility and polymorphism.(2)The chloroplast genomes of 6 Pleione species were sequenced by high-throughput sequencing technology and the chloroplast genome structure and sequence characteristics of other species in the genus were compared and analyzed.The cp genome of Pleione species exhibited a conserved tetrad structure and each species encoded 135 protein-coding genes,38 t RNA and 8 RNA genes;the cp genome length of the Pleione species in this study were 157964-159269 bp and the length of LSC,SSC and IR were 85953-87172 bp,18499-18712 bp and 26459-26756 bp,respectively.Palindromic and forward repeats accounted for a high proportion and the SSRs were mainly mononucleotide repeats in Pleione.Analysis of chloroplast sequence differences indicated that the differences in coding regions were smaller than those in non-coding regions,and the variation in LSC and SSC regions was greater than that in IR regions.Phylogenetic analysis showed that all Pleione species inferred from the cp genome were clustered together and received high support.(3)The potential geographical distribution of Pleione bulbocodioides and Pleione yunnanensis in the current period is simulated,and the change in the distribution of suitability of the two species under different climate warming scenarios(RCP4.5 and RCP8.5)in the future period(2041-2080)is predicted by combining climate and topographical variables through the Maxent model.The study shows that the model predicts results with high accuracy.Temperature seasonality,mean temperature of coldest quarter and precipitation of warmest quarter were the main ecological factors affecting the distribution of Pleione bulbocodioides;Emperature seasonality,mean temperature of driest quarter,precipitation of warmest quarter and elevation were the main environmental factors affecting the distribution of Pleione yunnanensis.At present,the potentially suitable habitat areas of Pleione bulbocodioides and Pleione yunnanensis are 209.04×10~4 km~2 and 67.73×10~4 km~2,respectively.The high suitable habitats are 78.01×10~4 km~2 and 14.02×10~4 km~2,the medium suitable habitats are 66.08×10~4 km~2 and 22.21×10~4 km~2,and the low suitable habitats are 64.95×10~4 km~2 and 31.50×10~4 km~2,respectively.(4)The simulation found that most of the suitable habitat areas of Pleione bulbocodioides and Pleione yunnanensis showed fragmented and discontinuous distribution,the highly suitable habitat areas show sporadic distribution by Arc GIS models.Although the potential habitat area of Pleione bulbocodioides and Pleione yunnanensis will increase under future climate scenarios,the species may be at greater risk of extinction if illegal mining is not discouraged.The suitable habitat of Pleione bulbocodioides will expand to the eastern region,the distribution of Pleione yunnanensis is mainly concentrated in the southwest region and the distribution area shows a trend of expanding from the central distribution area with the continuous warming of the climate.Therefore,on the one hand,the cultivation scale of the two species can be expanded in the suitable distribution area of the species to meet the development of the pharmaceutical industry,on the other hand,the species can be implemented in situ protection or the establishment of nature reserves.In addition,relevant laws and regulations should be improved and the protection of wild resources of the two species should be strengthened.