异型花柱是被子植物的一种花柱多态现象, 表现为具有交互式雌雄异位的花型间传粉的亲和性, 以及花型内和自交的不亲和性。而同型花柱(homostyly)是在异型花柱形成与演化中出现的一种雌雄蕊同长且自交亲和的花型。驼舌草属为白花丹科中较早出现二型花柱的属, 野外调查发现分布于新疆的驼舌草(Goniolimon speciosum)自然居群出现大量雌雄蕊同长(H)的花型, 类似于同型花柱。该花型的产生背景是否已转变为型内和自交亲和, 它与典型的长(L)/短(S)花柱型花之间的亲和性关系等问题尚不清楚。该研究对驼舌草5个自然居群的花型构成与频率、花部特征参数和柱头花粉负荷进行统计, 并检测附属多态性和异型不亲和系统。结果表明, 所有居群均由L、S和H三种花型构成, 但在花粉纹饰和柱头表皮细胞形态上仍具二型性和严格的非选型交配, 表现为花粉纹饰和柱头乳突细胞形态不同的花型间亲和, 反之则不亲和。研究表明, H型花可能是由L型和S型花的雌雄蕊间距缩短所致, 是花型间交互式雌雄异位变异的结果, 但该花型并未转变为同型花柱。对于该物种而言, 这种交互式雌雄异位的变异与生理不亲和性的转变可能相对独立。

Heterostyly is a kind of floral morph polymorphism in angiosperms, which is characterized by the reciprocal herkogamy and accompanied by physiological self- and intra-incompatibility but inter-compatibility. And the homostyly (H) is a kind of self-compatible floral morph with stigmas and anthers at the same position within a flower, which occurs during the formation and evolution of heterostyly. It has been reported that distyly appeared earlier in Goniolimon than in other genus in the Plumbaginaceae. However, our field survey found that a large number of floral morphs with the same length of pistils and stamens (H-morphs) appeared in the natural population of Goniolimon speciosum in Xinjiang, similar to homostyly. It is not clear how the H-morphs emerge, whether the H-morphs have been self- and intra-compatible, and what kind of relationship between the H-morphs and the typical floral morphs with long- (L-) or short- (S-) style flower. Thus, we investigated the floral morph composition and frequency, measured the floral parameters and stigmatic pollen loads among floral morphs, and also examined the accessory polymorphism and heteromorphic incompatibility system of G. speciosum in five natural populations. The result showed that all populations were composed of L-, S- and H-morphs, but each population still had dimorphism of pollen-stigma morphology and strictly disassortative mating, which showed that the floral morphs with different pollen ornamentation and stigma papilla cell morphology were compatible regardless of the reciprocal herkogamy, but incompatible if the floral morphs were the same. Conclusion: H-morphs may the result of the variation of reciprocal herkogamy between floral morphs by shortening of stigma in L-morph or shortening of anther in S-morphs, but have not transformed into the homostyly. For this species, the variation of reciprocal herkogamy and the transformation of physiological incompatibility may be independent of each other.