Cytology And Molecular Evolution Of The Tribe Convallarieae

The Convallarieae s.l.includes six genera: Convallaria,Speirantha,Reineckia,Rhodea,Tupistra and Aspidistra,which are widely distributed in the northern hemisphere,especially in China and Japan.All these genera of Convallarieae all have stable chromosome numbers and prominent karyotype characteristics except Aspidistra,which makes them the ideal groups for studying the evolution of plant chromosomes.The phylogenetic position and the evolutionary relationship among genera of Convallarieae have been controversial.There is a contradiction between morphological classification and molecular phylogeny of Convallarieae.Based on the collection and collation of chromosome data and the latest results of molecular phylogeny,this study aims to explore the phylogenetic relationship among various groups in the family,and to explore the relationship between chromosome evolution and their phylogenetic relationships.In this study,the latest molecular phylogenetic framework of Convallarieae was constructed by sequencing four chloroplast gene fragments(rbcl,mat K,psb A-trn H and trn L-F)and nuclear gene of ITS.The chromosome number and karyotype evolution trend of Convallarieae were discussed,which provided cytological support for the relationship between genera and species.This thesis discussed about Chromosome number and karyotype of 5 species of Convallarieae,i.e.,Aspidistra elation,Aspidistra hainanensis,Aspidistra sichuanensis,Aspidistra fenghuangensis,and Rohdea japonica.The results showed that the chromosome number of 4 species of Convallarieae was 2n=38,except for Aspidistra elatior,which was 2n=36.Aspidistra sichuanensis(2n=38=24m+6sm+8st)has close relationship with Aspidistra fenghuangensi(2n=38=18m+14sm+6st),which share similar karyotype and the same asymmetric of 2C.Finally,all the reported genera,species and chromosome numbers of Convallarieae were collected comprehensively,including 81 species and 253 chromosome records of 7 genera(including Campylandra).Statistical analyses show that the number of chromosomes in Convallarieae was 2n=38,and the chromosome base was x=19.Only some plants in the genus Aspidistra had2n=36,and the chromosome base was x=18,and a few were tetraploid and hexaploid.In addition,further exploration was conducted on the phylogenetic relationships of Convallarieae with total of 64 species,including 10 newly sequenced and others obbtained from Gen Bank.Chrloroplast sequences of rbc L,mat K,psb A-trn H and trn L-F and ITS nuclear gene of ITS were selected for phylogenetic study.The main study results based on nuclear and chloroplast sequence suggested that the Convallarieae is divided into three major lineages:(1)the Convallaria-Speirantha clades(BS=95%),including Convallaria and Speirantha;(2)Rhodea-Reineckia clades(BS=98%),including Rhode,Campylandra and Reineckia;(3)Tupistra-Aspidistra clades(BS=97%),including Aspidistra,Tricalistra and Tupistra.According to the results of molecular phylogenetic analysis,the chromosome base of Convallaria and Speirantha at the base of Convallarieae is x=19,and the variation of their length is gradually decreasing,which belongs to Convallaria type;the second clades formed by Rhodea?Reineckia and Campylandra is the same as the chromosomal type of the first one,which also belongs to Convallaria type;the third branch is composed of Aspidistra,Tricalistra and Tupistra with both Aspidistra type and Tupistra type.The evolutionary trend of karyotype of this tribe indicates that the Convallaria type is primitive,followed by the derived Tupistra type and the Aspidistra type.The results show that the low base x=18 evolved probably from x=19 through chromosome fusion or loss in the tribe,with the karyotype evolved from the unimodal to the trimodal.The evolutionary direction of karyotype type from symmetry to asymmetry in Convallarieae is consistent with that of other higher plants.