花柱卷曲性的维持及功能性别特化

Maintenance and functional gender specialization of flexistyly

花柱多态型的型比通过选型交配形成的负频率依赖的选择来维持。种群空间格局对于频率依赖选择所维持的花柱多态型是至关重要的。该研究使用摆放实验构建不同型比的马来良姜(Alpinia mutica)人工种群,以评价花柱卷曲性促进选型交配的功能。使用邻域模型调查了云南草蔻(Alpinia blepharaocalyx)种群中的目标植株的坐果数、结籽数及其邻域中花序的数量和型偏以探讨在局域尺度上目标植株的雌性适合度是否受负频率依赖的选择。通过比较云南草蔻上举型和下垂型各繁殖性状的差异以及两型的功能性别的计算以评估两型功能性别可能存在的特化趋势。摆放实验结果说明花柱卷曲性形成的二型种群可以促进型间花粉传递。在局域尺度上,云南草蔻两型倾向于同型聚集分布,这一分布特点反映出其克隆生长特性。统计结果说明:邻域中异型花粉供体相对丰富度对两型目标植株都无影响;目标植株雌性适合度在邻域中不受负频率依赖选择的影响。这一结果并不支持负频率依赖的选择在该研究尺度上是影响种群型比结构的主要机制。云南草蔻两型个体在花期和果期的繁殖指标上不存在显著差异;功能性别计算结果显示选型交配是种群内唯一的交配模式时,下垂型功能性别偏雌性而上举型功能性别偏雄性。这一功能性别特化的趋势可能是通过对上举型的雄性功能的选择而造成的,并可能与种群型结构相关。当功能性别计算只考虑自交而忽略近交衰退时,种群功能性别偏向雌性。

Aims In stylar polymorphous species,the morph ratios are maintained by negative frequency-dependent selection through disassortative mating.The spatial context of a population is of crucial importance to maintain this stylar polymorphism.Under particular circumstances,disassortative mating in such species may promote the evolution of a dimorphism by gender specialization.We asked whether flexistyly can promote sufficient disassortative mating,whether the female fitness of focal plant is affected by negative frequency-dependent selection at local level,and whether the two morphs in flexistylous plants differ in gender specialization.Methods We used open-pollinated flexistylous Alpinia mutica to compare fertility in anaflexistylous,cataflexistylous and dimorphic arrays.Second,we used neighborhood models to investigate spatial distribution of morphs at local level within the population on reproductive output in the flexistylous,A.blepharaocalyx.We quantified the distribution of the morphs in terms of neighborhood morph bias.We then measured the effect of neighborhood morph bias on open-pollinated reproductive output.Third,the reproductive characters were examined in anaflexistylous and cataflexistylous morphs of A.blepharaocalyx.We assessed functional genders of two morphs based on their allocations associated with times-dependent mating opportunities and the mean number of seeds produced by anaflexistylous and cataflexistylous plants with morph frequency in the population.Important findings Dimorphic arrays have higher female fertility than monomorphic arrays,demonstrating the flexistyly promotes inter-morph pollen transfer.Results from A.blepharaocalyx indicate that at the neighborhood scale,the two morphs have an aggregate distribution due to clonal growth.At this scale,focal plants showed no evidence of frequency-dependent total fruits and seeds per plant or seeds per flower.These results do not support frequency-dependent selection as a major mechanism affecting morph frequencies in A.blepharaocalyx within the context of this study.There are no significant differences between two morphs in flower and fruit characters.Functional gender analyses indicate that when illegitimate fertilization is negligible,the morphs are specialized in their later sexual functions,mediated by anaflexistylous morph through male fitness gained;however,when self-fertilization is included,the two morphs are both specialized in their female functions due to the lack of inbreeding depression in the formulas.