Department of Biology, University of Maryland, College Park, MD 20742, USA.
Oecologia. 2012 Feb;168(2):439-48. doi: 10.1007/s00442-011-2095-9. Epub 2011 Aug 11.
Nursery pollination, in which insects use as hosts the very plants they pollinate, ranges from obligate mutualism to parasitism. In the non-obligate interaction between Greya moths and the host Lithophragma sp., the relative density of nursery pollinators and copollinators, which do not use plant tissues for larval development, is a key determinant of the interaction's outcome. Silene (Caryophyllaceae) nursery pollination by Hadena moths (Lepidoptera: Noctuidae), studied primarily in Europe, is considered antagonistic because copollinators comprise a substantial proportion of the pollinator community. However, there are few studies that ascertain the direction of the Silene-Hadena interaction by taking into account both pollinator service and seed predation. Here, we report a novel comprehensive evaluation of the direction of the interaction between North American Hadena ectypa on Silene stellata, by comparing the relative contributions of nursery and copollinators to S. stellata pollination and relate this to variation in fruit predation and reproductive success of S. stellata across multiple sites and years. Hadena ectypa pollinator importance (pollen deposited/visit/h) varied between years, resulting from variable visitation rate. Copollinator importance was higher than H. ectypa in 1 year and equivalent in another. In two of three sites, lowered H. ectypa activity was not correlated with a significant decrease in plant reproductive success, indicating a negative interaction. Although pollinator service by H. ectypa is substantial in this system, copollinators' service is at least as great, and when the cost of fruit predation is factored in, the net effect of the interaction is parasitism of host plants.
苗圃授粉，即昆虫以其授粉的植物为宿主，其范围从专性互利共生到寄生。在灰蝶和 Lithophragma 属植物之间的非专性相互作用中，不使用植物组织进行幼虫发育的苗圃传粉者和共传粉者的相对密度是决定相互作用结果的关键因素。Silene（石竹科）由夜蛾科的 Hadena 蛾（鳞翅目）进行苗圃授粉，主要在欧洲进行研究，被认为是拮抗的，因为共传粉者构成了传粉者群体的很大一部分。然而，很少有研究通过考虑传粉服务和种子捕食来确定 Silene-Hadena 相互作用的方向。在这里，我们通过比较苗圃和共传粉者对 Silene stellata 授粉的相对贡献，并将其与多个地点和年份的 Silene stellata 果实捕食和繁殖成功率的变化相关联，报告了一种对北美 Hadena ectypa 对 Silene stellata 的相互作用方向的新的综合评估。Hadena ectypa 传粉者的重要性（花粉沉积/访问/h）因访问率的变化而在不同年份有所不同。在一年中，共传粉者的重要性高于 H.ectypa，而在另一年中则相等。在三个地点中的两个地点，Hadena ectypa 活性的降低与植物繁殖成功率的显著下降无关，表明存在负相互作用。尽管在这个系统中，H.ectypa 的传粉服务是实质性的，但共传粉者的服务至少同样大，并且当考虑到果实捕食的成本时，相互作用的净效应是寄生宿主植物。
