Institute for Global Food Security, School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK.
DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, 6140, South Africa.
Sci Rep. 2018 Sep 24;8(1):14282. doi: 10.1038/s41598-018-32728-0.
The spread of invasive species continues to reduce biodiversity across all regions and habitat types globally. However, invader impact prediction can be nebulous, and approaches often fail to integrate coupled direct and indirect invader effects. Here, we examine the ecological impacts of an invasive higher predator on lower trophic groups, further developing methodologies to more holistically quantify invader impact. We employ functional response (FR, resource use under different densities) and prey switching experiments to examine the trait- and density-mediated impacts of the invasive mosquitofish Gambusia affinis on an endemic intermediate predator Lovenula raynerae (Copepoda). Lovenula raynerae effectively consumed larval mosquitoes, but was naïve to mosquitofish cues, with attack rates and handling times of the intermediate predator unaffected by mosquitofish cue-treated water. Mosquitofish did not switch between male and female prey, consistently displaying a strong preference for female copepods. We thus demonstrate a lack of risk-reduction activity in the presence of invasive fish by L. raynerae and, in turn, high susceptibility of such intermediate trophic groups to invader impact. Further, we show that mosquitofish demonstrate sex-skewed predator selectivity towards intermediate predators of mosquito larvae, which may affect predator population demographics and, perversely, increase disease vector proliferations. We advocate the utility of FRs and prey switching combined to holistically quantify invasive species impact potential on native organisms at multiple trophic levels.
入侵物种的扩散继续在全球所有地区和生境类型中减少生物多样性。然而，入侵物种的影响预测可能并不明确，而且方法往往未能整合直接和间接入侵物种的耦合效应。在这里，我们研究了一种入侵的高级捕食者对低营养级群的生态影响，进一步开发了更全面地量化入侵物种影响的方法。我们采用功能反应（FR，在不同密度下的资源利用）和猎物转换实验来研究入侵的食蚊鱼 Gambusia affinis对本地中间捕食者Lovinula raynerae（桡足类）的特性和密度介导的影响。Lovinula raynerae 有效地消耗了幼虫蚊子，但对食蚊鱼的线索一无所知，中间捕食者的攻击率和处理时间不受食蚊鱼线索处理水的影响。食蚊鱼不会在雄性和雌性猎物之间转换，始终对雌性桡足类表现出强烈的偏好。因此，我们证明了 L. raynerae 在存在入侵鱼类的情况下没有减少风险的活动，并且这种中间营养级群容易受到入侵物种的影响。此外，我们表明，食蚊鱼对蚊子幼虫的中间捕食者表现出性别偏向的捕食者选择性，这可能会影响捕食者种群的人口统计学特征，并且反常地增加了疾病传播媒介的繁殖。我们主张采用 FR 和猎物转换相结合的方法，全面量化入侵物种对多个营养级别的本地生物的潜在影响。
