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Exotic weevil invasion increases floral herbivore community density, function, and impact on a native plant

花匠小妙招
2025-01-27 05:03

摘要

Consumer communities are being re-arranged through unprecedented rates of human-mediated invasions and extinctions. Such changes in consumer diversity potentially alter community function and impact on resource populations. Although insect herbivore invasions are increasingly common, the influence of such species additions on native resident herbivore guilds, along with their individual and combined effects on native plant resources, are rarely investigated. Here, we used site-to-site and plant-to-plant variation in herbivore composition to examine how the addition of an invasive exotic weevil, Rhinocyllus conicus, combines with a guild of native floral herbivores (tephritid flies, pyralid moths) to influence two key components of herbivore community function aggregate herbivore densities and cumulative levels of seed destruction on a native thistle, Cirsium canescens. Invasion of a site by R. conicus more than doubled aggregate herbivore density, resulting in increased levels of seed destruction and a halving of seed production by the native thistle. Further, herbivore function was significantly higher on individual plants attacked by R. conicus, compared to plants attacked only by native herbivores. Insect densities and levels of seed destruction on plants attacked by multiple herbivore taxa never exceeded those observed for plants attacked by R. conicus alone, suggesting that increases in herbivore community function with invasion resulted from the inclusion of a functionally dominant insect rather than any complementarity effects. Some evidence for interference between insects emerged, with a trend towards reduced moth and weevil densities in two and three taxon mixtures compared with plants attacked by each taxon alone. However, density compensation was limited so that, overall, the addition of a novel herbivore to the floral guild was associated with a significant increase in herbivore community function and impact on seed production. The results suggest that invasion of a functionally dominant herbivore into an unsaturated recipient community can augment function within a resource guild.展开▼

机译：消费者社区正以前所未有的人类介导的入侵和灭绝速度进行重新安排。消费者多样性的这种变化可能会改变社区的功能并影响资源人口。尽管昆虫食草动物的入侵日益普遍，但很少研究这类物种对当地食草动物行会的影响，以及它们对原生植物资源的个体和综合影响。在这里，我们使用了草食动物组成的站点到站点和植物到植物的变化，以检查入侵性外来象鼻犀（Rhinocyllus conicus）的添加与天然花草食动物群（te蝇，拟除虫蛾）的组合如何影响草食动物群落功能的两个关键组成部分聚集了草食动物密度，以及在本地蓟（Cirsium canescens）上种子破坏的累积水平。圆锥菌对位点的入侵使草食动物的聚集体密度增加了一倍以上，导致种子破坏水平提高，而当地蓟草的种子产量减半。此外，与仅受到天然食草动物攻击的植物相比，在食圆锥菌攻击的单个植物上的草食动物功能明显更高。受到多种食草动物类群侵袭的植物的昆虫密度和种子破坏水平从未超过仅受圆锥角锥菌侵袭的植物所观察到的昆虫密度和种子破坏水平，这表明食草动物群落随着入侵而增加的功能是由于纳入了功能优势昆虫而不是任何互补效应。出现了一些昆虫之间相互干扰的证据，与单独使用每个分类单元攻击的植物相比，存在两种和三种分类单元混合物中蛾和象鼻虫密度降低的趋势。但是，密度补偿受到限制，因此，总的来说，向花艺协会添加新的食草动物与食草动物群落功能的显着提高以及对种子生产的影响有关。结果表明，功能上占优势的草食动物侵入不饱和的受体群落可以增强资源公会的功能。展开▼