The switch to parasitism on an ecological and evolutionary scale

在生态和进化层面上向寄生的转变

• 批准号: 435245-2013
• 负责人: Luong, Lien
• 金额: $ 1.89万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=658117
• 关键词: switch; parasitism; ecological; evolutionary; scale

Pathogenic organisms that are harmless under certain conditions can suddenly become extremely harmful under different circumstances. Indeed levels of parasitism vary continuously in nature, with some species shifting along a continuum from benign to pathogenic over ecological and evolutionary time. But even more fundamental to this issue is the process by which parasitism per se evolved. Understanding the ecological and evolutionary factors that facilitate the acquisition of parasitism is important because it allows epidemiologists to more accurately predict when and where infectious diseases will emerge, and develop effective control measures. I will investigate the life-history evolution of parasites that express variation in host exploitation strategies, and identify the selective pressures that lead to the transition to a parasitic lifestyle. Facultative parasites present a unique and interesting opportunity for addressing these questions because they regularly shift from free-living to parasitic lifestyles. The facultative ectoparasitic mite, Macrocheles subbadius feeds and reproduces on highly ephemeral habitats - rotting cacti. However, mites become parasitic under certain circumstances by attaching to and feeding on cactophilic drosophilid hosts. Therefore, it appears the mites are capable of context-dependent expression of infectivity (ability to parasitize a host). The flies and mites co-occur naturally in the wild and are highly amendable to laboratory microcosm experiments. I plan to manipulate environmental conditions to test the ecological consequences of environmental heterogeneity on mite behaviour and infection (aim 1). To determine the heritability of the infectivity trait, I will perform experimental evolution by artificially selecting for mites with divergent levels of infectivity; the selected lines will be used to measure the evolutionary trade-offs between the evolution of parasitism and other key parasite life history traits (aim 2). Additionally, I will identify the ecological factors that select for increased reliance on hosts over a long period of time, i.e., the evolutionary transition to parasitism (aim 3). ************

在某些条件下无害的致病生物在不同情况下可能会突然变得非常有害。的确，寄生虫的水平在自然界中持续不断变化，有些物种沿着良性和进化时间的连续性从良性转移到致病性。但是，这个问题更重要的是寄生虫本身发展的过程。了解有助于获取寄生虫的生态和进化因素很重要，因为它允许流行病学家更准确地预测何时以及何时出现传染病，并制定有效的控制措施。我将研究表达宿主开发策略变化的寄生虫的生活历史演变，并确定导致过渡到寄生生活方式的选择性压力。教师寄生虫为解决这些问题提供了一个独特而有趣的机会，因为它们经常从自由生活转变为寄生生活方式。辅助性外寄生虫螨，宏观雪badius的饲料和繁殖高度短暂的栖息地 - 腐烂的仙人掌。然而，在某些情况下，螨虫通过附着并以仙人掌果蝇宿主为食而成为寄生虫。因此，螨虫似乎能够具有上下文依赖性感染性的表达（寄生寄主的能力）。苍蝇和螨虫自然在野外同时发生，并且对实验室缩影实验具有高度的修正。我计划操纵环境条件，以测试环境异质性对螨虫行为和感染的生态后果（AIM 1）。为了确定感染性状的遗传力，我将通过人为地选择具有不同感染性水平的螨虫来执行实验进化。选定的线将用于衡量寄生虫的演变与其他关键寄生虫生命历史特征之间的进化权衡（AIM 2）。此外，我将确定长时间选择增加对宿主的依赖的生态因素，即进化向寄生虫的过渡（AIM 3）。 ************