Doubleday Laura A D, Adler Lynn S
Graduate Program in Organismic and Evolutionary Biology University of Massachusetts Amherst Amherst MA USA.
Graduate Program in Entomology University of Massachusetts Amherst Amherst MA USA.
Ecol Evol. 2017 May 23;7(13):4694-4703. doi: 10.1002/ece3.3014. eCollection 2017 Jul.
Dioecy, a breeding system where individual plants are exclusively male or female, has evolved repeatedly. Extensive theory describes when dioecy should arise from hermaphroditism, frequently through gynodioecy, where females and hermaphrodites coexist, and when gynodioecy should be stable. Both pollinators and herbivores often prefer the pollen-bearing sex, with sex-specific fitness effects that can affect breeding system evolution. Nursery pollination, where adult insects pollinate flowers but their larvae feed on plant reproductive tissues, is a model for understanding mutualism evolution but could also yield insights into plant breeding system evolution. We studied a recently established nursery pollination interaction between native moths and introduced gynodioecious plants in North America to assess whether oviposition was biased toward females or hermaphrodites, which traits were associated with oviposition, and the effect of oviposition on host plant fitness. Oviposition was hermaphrodite-biased and associated with deeper flowers and more stems. Sexual dimorphism in flower depth, a trait also associated with oviposition on the native host plant (), explained the hermaphrodite bias. Egg-receiving plants experienced more fruit predation than plants that received no eggs, but relatively few fruits were lost, and egg receipt did not significantly alter total fruit production at the plant level. Oviposition did not enhance pollination; egg-receiving flowers usually failed to expand and produce seeds. Together, our results suggest that oviposition does not exert a large fitness cost on host plants, sex-biased interactions can emerge from preferences developed on a hermaphroditic host species, and new nursery pollination interactions can arise as negative or neutral rather than as mutualistic for the plant.
雌雄异株，即个体植物仅为雄性或雌性的一种繁殖系统，已经多次进化。广泛的理论描述了雌雄异株何时应从雌雄同体中产生，通常是通过雌全异株，即雌性和雌雄同体共存的情况，以及雌全异株何时应保持稳定。传粉者和食草动物通常都更喜欢产生花粉的性别，其具有性别特异性的适合度效应，这可能会影响繁殖系统的进化。苗圃传粉，即成年昆虫为花朵传粉但其幼虫以植物生殖组织为食，是理解互利共生进化的一个模型，但也可能为植物繁殖系统的进化提供见解。我们研究了北美本地蛾类与引入的雌全异株植物之间最近建立的苗圃传粉相互作用，以评估产卵是否偏向雌性或雌雄同体，哪些性状与产卵相关，以及产卵对寄主植物适合度的影响。产卵偏向雌雄同体，且与更深的花朵和更多的茎有关。花朵深度的性别二态性，这一性状也与在本地寄主植物上产卵有关，解释了对雌雄同体的偏好。接受卵的植物比未接受卵的植物遭受更多的果实捕食，但损失的果实相对较少，并且接受卵并没有显著改变植物水平上的总果实产量。产卵并没有增强授粉；接受卵的花朵通常无法开放并产生种子。总之，我们的结果表明，产卵不会对寄主植物造成很大的适合度成本，性别偏向的相互作用可能源于在雌雄同体寄主物种上形成的偏好，并且新的苗圃传粉相互作用对植物而言可能以负面或中性而非互利的形式出现。
