Hawkesbury Institute for the Environment, Hawkesbury Campus, Western Sydney University, Science Rd, Richmond, NSW, 2753, Australia.
BMC Evol Biol. 2018 Dec 14;18(1):193. doi: 10.1186/s12862-018-1314-y.
Obligate pollination mutualisms (OPMs) are specialized interactions in which female pollinators transport pollen between the male and female flowers of a single plant species and then lay eggs into those same flowers. The pollinator offspring hatch and feed upon some or all of the developing ovules pollinated by their mothers. Strong trait matching between plants and their pollinators in OPMs is expected to result in reciprocal partner specificity i.e., a single pollinator species using a single plant species and vice versa, and strict co-speciation. These issues have been studied extensively in figs and fig wasps, but little in the more recently discovered co-diversification of Epicephala moths and their Phyllanthaceae hosts. OPMs involving Epicephala moths are believed occur in approximately 500 species of Phyllanthaceae, making it the second largest OPM group after the Ficus radiation (> 750 species). In this study, we used a mixture of DNA barcoding, genital morphology and behavioral observations to determine the number of Epicephala moth species inhabiting the fruits of Breynia oblongifolia, their geographic distribution, pollinating behavior and phylogenetic relationships.
We found that B. oblongifolia hosts two species of pollinator that co-occurred at all study sites, violating the assumption of reciprocal specificity. Male and female genital morphologies both differed considerably between the two moth species. In particular, females differed in the shape of their ovipositors, eggs and oviposition sites. Phylogenetic analyses indicated that the two Epicephala spp. on B. oblongifolia likely co-exist due to a host switch. In addition, we discovered that Breynia fruits are also often inhabited by a third moth, an undescribed species of Herpystis, which is a non-pollinating seed parasite.
Our study reveals new complexity in interactions between Phyllantheae and Epicephala pollinators and highlights that host switching, co-speciation and non-pollinating seed parasites can shape species interactions in OPMs. Our finding that co-occurring Epicephala species have contrasting oviposition modes parallels other studies and suggests that such traits are important in Epicephala species coexistence.
专性传粉互惠共生（OPM）是一种特殊的相互作用，其中雌性传粉者在同一植物物种的雄花和雌花之间运输花粉，然后将卵产入同一朵花中。传粉者的后代孵化并以其母亲授粉的一些或所有发育中的胚珠为食。在 OPM 中，植物与其传粉者之间的强烈性状匹配预计会导致互惠伙伴特异性，即单一传粉者物种使用单一植物物种，反之亦然，以及严格的共同进化。这些问题在榕属植物和榕小蜂中已经得到了广泛研究，但在最近发现的 Epicephala 飞蛾及其 Phyllanthaceae 宿主的共同进化中研究甚少。据信，涉及 Epicephala 飞蛾的 OPM 发生在大约 500 种 Phyllanthaceae 物种中，使其成为继榕属植物辐射（>750 种）之后的第二大 OPM 群体。在这项研究中，我们使用 DNA 条形码、生殖器形态和行为观察的混合物来确定栖息在 Breynia oblongifolia 果实中的 Epicephala 飞蛾物种的数量、它们的地理分布、传粉行为和系统发育关系。
我们发现，B. oblongifolia 宿主两种同时存在于所有研究地点的传粉者，违反了互惠特异性的假设。两种飞蛾的雄性和雌性生殖器形态都有很大的不同。特别是，雌性在产卵器、卵和产卵部位的形状上有所不同。系统发育分析表明，B. oblongifolia 上的两种 Epicephala spp. 可能由于宿主转换而共存。此外，我们发现 Breynia 果实还经常被第三种飞蛾，一种未命名的 Herpystis 物种栖息，它是一种非传粉的种子寄生虫。
我们的研究揭示了 Phyllantheae 和 Epicephala 传粉者之间相互作用的新复杂性，并强调了宿主转换、共同进化和非传粉的种子寄生虫可以塑造 OPM 中的物种相互作用。我们发现共存的 Epicephala 物种具有不同的产卵模式与其他研究相似，表明这些特征在 Epicephala 物种共存中很重要。
