ABSTRACT

The origin and establishment of gender dimorphism has been postulated as a key element in the evolution of insular floras but has generally not been studied in an explicit phylogenetic framework. We tested the prior conclusion that the origin of gender dimorphism in the New Zealand species of Gaultheria Kalm ex L. is allochthonous by newly tracing the evolution of gender dimorphism on a phylogenetic tree of the Wintergreen Clade. We scored species for male sterility and breeding system type (cosexual, gynodioecious, or dioecious) based on the literature, and observations from the field and herbarium specimens. We traced the evolution of gender dimorphism, fruit evolution, and ancestral areas on the tree with parsimony, maximum likelihood, and Bayesian methods. Our analyses revealed that male sterility in New Zealand most likely emanated from a male-sterile fleshy red-fruited South American lineage, with reversals to cosexuality in two or three Australian lineages of the more inclusive Australasian Clade. The results support an allochthonous origin of gynodioecy in New Zealand Gaultheria and corroborate arrival of the ancestral ancestor through over-water dispersal, likely by birds. Although gender dimorphism could have arrived to New Zealand as a preadaptation to avoid inbreeding depression in an island setting, its correlation with fleshy fruit, unspecialised flowers, and woody habit across the genus suggests that factors other than the island setting per se are responsible for its maintenance in New Zealand. Although gender dimorphism in New Zealand has usually arisen autochthonously in dry-fruited genera, in Gaultheria the presence of gynodioecy in several dry-fruited species is best explained by its retention from fleshy-fruited ancestors.

摘要

性别二态性的起源和建立被认为是岛内菌群进化的关键因素，但通常没有在明确的系统发育框架中进行研究。我们测试了先前的结论，即新西兰Gaultheria物种中性别二态性的起源Kalm ex L.是通过在Wintergreen Clade的系统发育树上新追踪性别二态性进化而异源的。我们根据文献以及田间和植物标本室的观察结果，对雄性不育和繁殖系统类型（两性，雌雄同体或雌雄异体）的物种进行了评分。我们使用简约，最大似然和贝叶斯方法追踪了树上的性别二态性，果实进化和祖先区域的进化。我们的分析表明，新西兰的男性不育很可能源于雄性不育的肉质红色水果南美南美血统，在更具包容性的澳大利亚进化枝的两个或三个澳大利亚血统中逆转了性欲。结果支持gynodioecy在新西兰的外来起源冬青并通过水的扩散（可能是鸟类）来确认祖先的到来。尽管性别二元化可能是为了避免在岛屿环境中进行近亲衰退而进行的适应，但它与该属的肉质水果，非专业花和木本习性的相关性表明，除了岛屿环境本身以外的其他因素也可能是其原因。在新西兰进行维护。尽管新西兰的性别二态性通常是在干果属中自发产生的，但在Gaultheria中，几种干果物种中的雌雄同体存在可以通过保留在果肉祖先中得到最好的解释。