青藏高原5种石竹科垫状植物的核型研究

垫状植物是高山冰缘带植物区系的重要组成成分,是植物适应高寒环境趋同进化的特殊生活型。该研究以采自西藏和云南高山冰缘带的5种石竹科垫状植物种子为材料,采用滤纸萌发法、常规压片法镜检观察分析其核型,为青藏高原垫状植物积累核型资料,并为探讨极端环境下特殊生活型植物的核型进化机制提供依据。结果表明:5种植物均为二倍体,染色体核型分别为:密生福禄草(Arenaria densissima),2n=2x=20m+2sm,2A;山生福禄草(A.oreophila),2n=2x=22m,1A;团状福禄草(A.polytrichoides),2n=2x=20m+2sm,2A;大花福禄草(A.smithiana),2n=2x=20m+2sm,1A;囊种草(Thylacospermum caespitosum),2n=2x=18m+4sm,2A。囊种草与福禄草亚属植物的染色体数目一致,为二者在分子系统发育框架下形成的独立分支提供核型证据。并讨论了5种垫状植物古多倍体物种形成的核型进化与中新世青藏高原及周边地区地质抬升的关联。

Karyological Study of Five Cushion Plants of Caryophyllaceae in Qinghai Tibet Plateau

Cushion plants are important elements in alpine subnivalbelt flora, which are recognized as the production of adaptive convergence to cold and extreme environment in alpine zone. In this study, the seeds of five cushion plants of Caryophyllaceae were chosen asexperimental materials. These seeds that collected from the alpine subnival belt in Xizang and Yunnan, germinated on wet filter papers. Roottipsquashmethod was used for cytological observation. The present study aims to accumulate karyological data for cushion plants in Qinghai Tibet Plateau (QTP), and then further to provide the basis for the exploration on karyotypic evolution mechanism of special life form plants in extreme environment of QTP. The results showed that five species are all diploid, and their karyotype formulae were showed as followed: Arenaria densissima, 2n = 2x = 20m + 2sm, 2A; A. oreophila, 2n = 2x = 22m, 1A; A. polytrichoides, 2n = 2x = 20m + 2sm, 2A; A. smithiana, 2n = 2x = 20m + 2sm, 1A; Thylacospermum caespitosum, 2n = 2x = 18m + 4sm, 2A. The chromosome numbers of T. caespitosum is consistent with that of Arenaria subg. Dolophragma. The results provide the karyological evidence for the independence of the new clade composed by abovementioned two taxa in the molecular phylogeny framework of Caryophyllaceae. Moreover, we discussed the association between the evolutionary history of paleopolyploid speciation exhibited by five studied cushion plants and the uplift of QTP and its surrounding region during the Miocene period.