Living on the edge: genetic variability and range dynamics of the American dog tick

生活在边缘：美国狗蜱的遗传变异和范围动态

• 批准号: RGPIN-2021-04376
• 负责人: Chilton, Neil
• 金额: $ 3.42万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=745646
• 关键词: Living; edge; genetic; variability; range

Each species has a unique geographical distribution. Range expansion by some species is in response to climate change. Detailed knowledge of the range and abundance of species across the landscape is particularly important if they are a vital food source, of cultural significance, keystone species at risk of extinction, invasive species, or parasites or microbes that affect the health of wildlife, domestic animals and humans. Tick-borne pathogens, for example, cause significant economic losses for cattle producers worldwide. Understanding what factors restrict the ranges of species remains a key issue in ecology and evolutionary biology. My long-term research goals are to understand how ecological and evolutionary factors influence the distribution and abundance of parasites, and to unveil the strength of parasitism and endosymbiosis as fundamental ecological interactions and drivers of selection. The centre-periphery hypothesis (CPH) postulates that individuals at the range edge experience harsher ecological conditions and have reduced fitness than those in more `core' populations. Populations at range edges are smaller, genetically less diverse and have reduced adaptive potential to cope with environmental conditions in habitats beyond the distributional limits. Although the CPH provides a general explanation as to what limits species distributions, its does not in its current form, represent a universal rule. Also, few studies have examined if the CPH is applicable to parasites, which comprise 30-50% of all animals. Over the next five years, we will use a unique combined approach (laboratory and field experiments with molecular tools) to uncover how genetic variation and species interactions influence tick distribution and abundance by examining three interrelated objectives: (1) compare the genetic diversity and divergence of tick populations near the range edges with more `core' populations, (2) examine the effect of predatory ants on tick survival and (3) elucidate if tick survival is influenced by bacterial endosymbionts. The third objective is unique, in that, the effect of endosymbionts on the survival of their tick hosts has largely been overlooked. The American dog tick (Dermacentor variabilis) is the focal organism of this study because it has a broad geographic range in North America that is expanding northwards and westwards in Saskatchewan. Advancing our understanding of what limits range expansion of D. variabilis will also be of importance for other researchers in the development of effective strategies to control this species, and other parasitic arthropod vectors and their pathogens that are currently expanding their ranges into Canada. My research program also facilitates the training of graduate and undergraduate students, future research leaders in Canada and other parts of the world, who will be well equipped to deal with the increasing economic and social burden of parasitic arthropods and their pathogenic microbes.

每个物种都有独特的地理分布。某些物种扩展范围是为了响应气候变化。如果它们是具有文化意义的重要食物来源，具有灭绝风险的基石物种，入侵物种，寄生虫或微生物影响野生动物的健康，家居动物的健康，那么对整个景观物种的范围和丰度的详细知识尤为重要。和人类。例如，tick传播的病原体会给全球牛生产者带来巨大的经济损失。了解哪些因素限制物种的范围仍然是生态学和进化生物学的关键问题。我的长期研究目标是了解生态和进化因素如何影响寄生虫的分布和丰度，并揭示寄生虫和内共生的强度，这是基本的生态相互作用和选择的驱动因素。中心围栏假说（CPH）假设，与更多“核心”人群的人相比，处于边缘的个人经历了更严格的生态条件并降低了适应性。范围边缘的种群较小，遗传学上的多样性较小，并且减少了适应性潜力，以应对分布限制以外的栖息地的环境条件。尽管CPH对哪些限制物种分布提供了一个普遍的解释，但其当前形式并不代表普遍的规则。而且，很少有研究检查CPH是否适用于寄生虫，该寄生虫占所有动物的30-50％。在接下来的五年中，我们将使用独特的合并方法（实验室和现场实验与分子工具）来揭示遗传变异和物种相互作用如何通过检查三个相互关联的目标来影响壁虱分布和丰度：（1）比较遗传多样性和差异。 （2）检查捕食蚂蚁对tick存活的影响，（2）阐明tick生存的影响是否受细菌内共生体的影响。第三个目标是独一无二的，因为内共生体对其tick宿主生存的影响很大程度上被忽略了。美国狗tick虫（Dermacentor variabilis）是这项研究的焦点生物，因为它在北美的地理范围广泛，在萨斯喀彻温省向北和向西扩展。促进我们对D. variabilis的限制范围扩展的理解对于其他研究人员的发展，在开发有效控制该物种的策略中，以及其他寄生虫节肢动物媒介及其病原体目前正在扩展到加拿大的范围。我的研究计划还促进了培训毕业生和本科生，加拿大未来的研究领袖以及世界其他地区的研究领袖，他们将有能力应对寄生虫节肢动物及其致病微生物的经济和社会负担不断增加的经济和社会负担。