天门冬科广义铃兰族的染色体数目与核型进化研究

Chromosome Numbers and Karyotype Evolution of Convallarieae s.l.(Asparagaceae)

广义铃兰族包括6属200余种单子叶植物,具有较为稳定的染色体数目以及明显的核型变化,是研究植物染色体进化非常理想的类群。该研究采用常规压片法对铃兰族5个物种植物的染色体形态、数目及其核型进行了观察分析,并全面收集和整理了铃兰族所有已报道的共81种253条的染色体记录,通过综合统计、重建系统发育树,探讨铃兰族属间以及各属下种间的系统关系,以揭示物种间的亲缘关系和起源演化趋势。结果表明:(1)细胞学实验观察发现,铃兰族5个物种植物的染色体数目除蜘蛛抱蛋为2n=36外,其余4种均为2n=38,且均为二倍体,不对称性核型均为Stebbins’-2C型,核型不对称系数As.K%的变化范围为65%~69%,但染色体核型公式有差别。(2)所收集的铃兰族染色体报道记录中,绝大多数物种的染色体数目为2n=38,只在蜘蛛抱蛋属中有部分物种为2n=36;根据染色体长度变化核型主要分为单型和三型;统计结果显示,染色体2n=36的类群比2n=38的类群通常多1对中型染色体,少2对小型染色体,推测可能是由于2对小的染色体融合成为1对中型染色体。(3)基于4个叶绿体基因片段(rbcL、matK、psbA-trnH和trnL-F)和核基因ITS构建的铃兰族最新分子系统发育树显示,铃兰族分为三支,第Ⅰ支位于整个族的基部,为首先分化出来的铃兰-白穗花分支,均以x=19为基数;第Ⅱ支为万年青-吉祥草分支,染色体基数为x=19;第Ⅲ支为蜘蛛抱蛋-长柱开口箭分支,染色体基数为x=18或19;结合铃兰族染色体基数和核型分析发现,铃兰族染色体低基数的x=18是由x=19通过染色体融合或丢失进化而来,推测核型则是由比较对称的单型向不对称的三型演化而来。该研究结果为铃兰族属间关系及物种进化关系提供了细胞学支持证据。

The study adopts the method of conventional tableting of 5 Convallarieae species.The shapes,chromosome number and karyotype of the observation analysis,and comprehensively collect all the Convallarieae has reported a total of 81 of the 253 published of chromosomes,through comprehensive statistics,reconstruction of phylogenetic tree,between the Convallarieae was studied and the subordinate relations between the systems,to reveal the relationship between species and the trend of origin and evolution.The results showed that:(1)the results of cytological experiments showed that the chromosome number of 4 species of Convallarieae was 2n=38,except for Aspidistra elatior,which was 2n=36,and all of them were diploid,and the asymmetry karyotype was Stebbins'-2C.The variation range of the asymmetry coefficient As.K%was from 65%to 69%,but the karyotype formula was different.(2)The chromosome number of most species is 2n=38,while that of some species in Aspidistra is 2n=36;according to the variation of chromosome length,the karyotypes were mainly divided into unimodal and trimodal.The statistical results show that the group with chromosome 2n=36 usually has one more pair of medium chromosomes and two less pairs of small chromosomes than the group with chromosome 2n=38,which may be due to the fusion of two small pairs of chromosomes into a pair of medium chromosomes.(3)The latest phylogenetic tree of Convallarieae based on four chloroplast gene fragments(rbcL,matK,psba-trnH and trnL-F)and nuclear gene ITS showed that Convallarieae was divided into three clades.TheⅠclade was located in the base of the whole clades and was the first to be differentiated from the Convallaria-Speirantha clades and the chromosome number is x=19;theⅡclade is the Rhodea-Reineckia clades,and the chromosome number is x=19;theⅢclade is the Tupistra-Aspidistra clades and the chromosome number is x=18 or 19.Based on the analysis of chromosome cardinality and karyotype of Convallarieae,the low number x=18 of Convallarieae evolved from x=19 through chromosomal fusion or loss.It is speculated that the karyotype evolved from a relatively symmetrical unimodal to an asymmetrical trimodal.This study provides cytological evidences to reveal the evolutionary relationships between genera and species within Convallarieae.