Simón-Porcar Violeta I, Meagher Thomas R, Arroyo Juan
Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Sevilla, Spain.
School of Biology, University of St. Andrews, St. Andrews, United Kingdom.
Evolution. 2015 Sep;69(9):2276-88. doi: 10.1111/evo.12731. Epub 2015 Aug 20.
Evolution to reduce inbreeding can favor disassortative (intermorph) over assortative (intramorph) mating in hermaphroditic sexually polymorphic plant species. Heterostyly enhances disassortative pollination through reciprocal placement of stigmas and anthers of morphs and appropriate pollinators. Stylar dimorphism in which there is not reciprocal anther placement may compromise disassortative mating, particularly when there is not intramorph incompatibility. Variable rates of disassortative mating along with differential female fecundity or siring success among floral morphs could lead to variation in morph ratio. We investigated mating patterns, female fecundity, and siring success of style-length morphs in Narcissus papyraceus, a self-incompatible but morph-compatible species with dimorphic (long- and short-styled) and monomorphic (long-styled) populations in central and north regions of its range, respectively. We established experimental populations in both regions and exposed them to ambient pollinators. Using paternity analysis, we found similar siring success of morphs and high disassortative mating in most populations. Female fecundity of morphs was similar in all populations. Although these results could not completely explain the loss of dimorphism in the species' northern range, they provided evidence for the evolutionary stability of stylar dimorphism in N. papyraceus in at least some populations. Our findings support the hypothesis that prevailing intermorph mating is key for the maintenance of stylar dimorphism.
在雌雄同体的性多态植物物种中，为减少近亲繁殖而发生的进化可能更有利于异配（形态间）而非同配（形态内）交配。花柱异长通过不同形态的柱头和花药的相互位置以及合适的传粉者促进异配授粉。花柱二型性中花药没有相互位置可能会损害异配交配，特别是当不存在形态内不亲和性时。不同的异配交配率以及不同花形态间雌性繁殖力或父本成功的差异可能导致形态比例的变化。我们研究了纸白水仙中花柱长度形态的交配模式、雌性繁殖力和父本成功情况，该物种是一种自交不亲和但形态兼容的物种，在其分布范围的中部和北部地区分别有二型（长花柱和短花柱）和单型（长花柱）种群。我们在这两个地区都建立了实验种群，并让它们暴露于自然传粉者中。通过父本分析，我们发现大多数种群中不同形态的父本成功情况相似且异配交配率高。所有种群中不同形态的雌性繁殖力相似。尽管这些结果不能完全解释该物种在北部地区二型性的丧失，但它们为至少一些种群中纸白水仙花柱二型性的进化稳定性提供了证据。我们的研究结果支持这样的假设，即普遍存在的形态间交配是维持花柱二型性的关键。
