新疆补血草属植物异型花柱的变异与演化研究

The evolution between heterostyly and sexual systems of gender separation in the true sense of plants has become the focus of attention by many scholars. Accumulated researches largely have confirmed speculation about heterostyly functions that early scientists had done such as Darwin etc., also enhanced understanding for people to heterostyly phenotypic characteristics and mating system. But so far it have been still poorly understood about the maintenance, variation and stable ecology evolutionary mechanism of flower phenotype polymorphism of heterostyly within species and genus. Plumbaginaceae has been reported to have heterostylous species and our latest investigation has shown that there were three major classes of stylar polymorphisms from a survey of six species in Limonium. These classes with stylar polymorphisms has certain functional characteristics of heterostyly in mating patterns and ancillary polymorphisms, but distinguished it from typical tristyly and distyly in terms of floral type combination. Limonium has been reported to have distyly specie distribution. What is the relationship between these styles polymorphism and distyly in the evolutionary sequences? and how the polymorphism is maintained in natural populations. To explore the variation and evolution process of heterostyly in Limonium, in the project we plan to investigate various aspects of pollination biology and breeding system of all species with styles polymorphism in the field populations in Xingjiang,including studies of the distribution of styles polymorphism in Limonium, floral syndrome including differences in style length and anther height, diallelic self-incompatibility, and a suite of ancillary pollen and stigma polymorphisms, pollination and mating patterns, the test of several hypotheses on maintenance of styles polymorphism and the investigation of their different pollination environments. We also investigate the current selective pressure in populations with styles polymorphism to track its evolutionary trend. All of these studies will be useful to clarify the pathway of occuring and evolution about heterostyly, to better understand diverse breeding systems in angiosperms.

异型花柱与真正实现性别分离的性系统间的演化成为很多学者关注的焦点。不断积累的研究很大程度上印证了达尔文等科学家对异型花柱功能的推测，也增进了人们对异型花柱表型特征及交配系统的理解。但目前对异型花柱植物花表型多态性在种、属内的维持、变异与稳定的进化生态学机制，仍知之甚少。白花丹科Plumbaginaceae被报道为有异型花柱分布较多的科。前期，我们对新疆补血草属6个种的居群进行了调查，显示出3种花型组合的居群类型。这些种具有异型花柱的主要特征，但花型组合上又不同于现已发现的二型和三型花柱。补血草属被报道为有二型花柱分布，这些花柱多态类型与二型花柱有怎样的关系？补血草属内异型花柱有怎样的变异和演化过程？为此，我们对该属花柱多态性的分布、花部综合症、传粉模式、交配系统、不同分布区域的环境因素以及当前居群的选择压力等进行研究。以探讨补血草属中异型花柱的变异和演化规律及被子植物多样化的繁育系统类型。

异型花柱是由遗传控制的一种花柱多态现象，表现为在一个居群内由两种或三种雌、雄蕊长度具交互性对应关系的花型构成。白花丹科被报道为有二型花柱分布较多的科，成为研究异型花柱在种、属内维持与演化的较好材料。项目组以分布在新疆的补血草属植物为研究对象，对其花柱多态性的分布、异型花柱综合征、传粉模式、异型不亲和系统等进行研究。结果显示：1)所调查居群具较大的变异性，共具5种花型、4种不同的花型组合。分别为长、短花柱L和S型花、雌雄蕊同长的H型花，以及雌蕊位于雄蕊之上或之下的AH和RH型花， 2）居群内各花型花大小、花粉量等花部特征参数无差异，但花粉纹饰、柱头乳突细胞形态具二型性，其中H、AH和RH型花的花粉、柱头形态分别与L或S型花一致。居群水平上，无论哪种花型组合，两种柱头类型的植株数等比。.3）多数居群有长、短吻两类传粉者，二者具有不同的花粉传递效率，在喀什补血草居群中只有短吻昆虫的盛花初期，高位性器官之间异花粉传递效率高于低位性器官，而在长吻昆虫为主的盛花中后期，高、低位性器官之间的花粉传递效率是对称的。与之相对应的花期各阶段也具明显不同的结实率。.3）所调查居群具典型的异型不亲和性；在雌雄蕊具交互性对应关系的花型间授粉具较高结实率，而在没有交互性对应关系的花型间授粉，表现为花粉纹饰、柱头乳突细胞形态不同的花型间亲和，反之不亲和。自然状态下，同一居群内各花型的自然结实率没有差异。在缺乏交互性对应关系的花型间授粉，柱头乳突细胞的形态和花粉纹饰间具相互识别作用，进而促进非选型交配和各花型的繁殖适合度，支持Dulberger（1975） 的“形态互补性假说”4）从花型构成与频率、花部参数、附属多态性及功能、异型不亲和系统的研究结果看：新疆境内的补血草属植物应为二型花柱演化过程中的中间过渡阶段。雌雄蕊同长的H型、AH和RH型花可能是由L或S型花演变而来，为控制长短花柱雌、雄蕊长度的基因突变所致。