Nontarget herbivory by a weed biocontrol insect is limited to spillover, reducing the chance of population-level impacts

Insects approved for classical biocontrol of weeds are often capable of using close relatives of their target weed for feeding, oviposition, or larval development, with reduced preference and performance. When nontarget herbivory occurs and is suspected to reduce survival, growth, or fecundity of individual plants, and insects are capable of reproducing on their nontarget host, characterization of spatial and temporal patterns of the occurrence and intensity of herbivory is valuable for predicting potential population-level effects. Here, we perform a novel post-release manipulative field experiment with a root-feeding biocontrol weevil, Mogulones crucifer, released in Canada to control the rangeland weed Cynoglossum officinale, to test for its ability to establish on the nontarget plant Hackelia micrantha. After Cynoglossum, M. crucifer exhibits its highest preference for and performance on Hackelia spp. We released M. crucifer on Canadian rangeland sites with naturally occurring popul...用于杂草经典生物防治（classical biocontrol）的昆虫，通常可利用靶标杂草的近缘物种完成取食、产卵或幼虫发育，但其寄主偏好性与适合度表现会有所降低。当发生非靶标植食性危害（nontarget herbivory）且疑似会降低单株植物的存活率、生长势或繁殖力，同时该昆虫能够在非靶标寄主上完成繁殖时，对植食性危害的发生时空格局与强度进行表征，对于预测其潜在的种群水平影响具有重要研究价值。本研究针对一种在加拿大释放用于防治牧场杂草药用牛舌草（Cynoglossum officinale）的食根型生物防治象甲——十字沟象甲（Mogulones crucifer），开展了一项新颖的释放后操控性田间试验，以验证其能否在非靶标植物小花鹤虱（Hackelia micrantha）上成功定殖。相较于靶标杂草药用牛舌草，十字沟象甲（Mogulones crucifer）对鹤虱属（Hackelia spp.）植物的取食偏好与适合度表现为所有非靶标宿主中最优。我们在加拿大的牧场样地中释放了十字沟象甲（Mogulones crucifer），这些样地自然存在自然种群[原文未完整表述]。