The Ecology & Evolution of Species Range Limits

生态学

• 批准号: RGPIN-2014-06011
• 负责人: Eckert, Christopher
• 金额: $ 5.76万
• 依托单位: Queen's University
• 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=649916
• 关键词: Ecology; Evolution; Species; Range; Limits

All organisms are limited in their geographic distribution, but how and why these range limits occur are poorly understood. What ecological processes enforce range limits over the short-term, and what genetic constraints prevent natural selection from enabling range expansion over the long term? This deficiency prevents realistic forecasting of whether species will shift their ranges or go extinct during climate change, and effective conservation strategies for Canadian species at risk, most of which occur in Canada at the northern limits of broader distributions south of the US border. My research seeks a better understanding of the ecology and evolution of range limits.**A species' distribution is thought to reflect its ecological niche: the conditions under which survival and reproduction are sufficient for sustainable populations. Areas where a species does not occur are simply outside of its niche. However, we recently analyzed studies that measured performance of species transplanted beyond their ranges and found that range limits did not coincide with niche limits in > 50% of all cases. Unfortunately, few studies were designed to provide definitive answers, so there is a clear need for more experiments. The dispersal capacity of a species may also constrain its distribution, but this remains speculative. We will combine large-scale geographic surveys, transplant experiments and genetic estimates of dispersal to test the relative contribution of niche limits vs dispersal to range limits.**Long-term evolutionary stasis of range limits is thought to arise because range-edge populations lack genetic variation in traits that would allow persistence beyond the limit, or because natural selection for improved performance at the limit is continually thwarted by the immigration of genes from larger populations towards the range centre. We will test these hypotheses by combining transplant experiments and genetic analyses of gene movement and the adaptive potential of edge populations.**Geographic range edges may be venues for significant evolution. For instance, some plants show striking range-edge changes in reproduction, often involving a shift from sexuality to asexuality. The loss of sex and thus genetic recombination at the range edge may reduce potential for further adaptation. On the other hand, asexuality can preserve unique combinations of genes advantageous in edge environments from being broken up by recombination. We will evaluate these hypotheses by comparing the performance of transplanted sexual and asexual genotypes in central vs edge habitats as well as testing for the genomic signature of long-term asexuality at range edges.**This research will help answer fundamental questions at the forefront of biology and contribute to the conservation of rare species, the management of exotic invaders, and better forecasting of species' responses to climate change; key environmental problems impinging on Canadian biodiversity. I will work with species proven to be excellent experimental subjects and experimental techniques we have used with success. The proposed research involves a range of highly transferable technical skills including modern genetic techniques, field biology in diverse ecosystems, experimental design, advanced statistical analysis and bioinformatics. As such it will provide trainees at all levels with research experiences and skills suited to their diverse interests and long-term career goals in academia, resource management and industry. Ongoing research partnerships with Parks Canada, Ontario MNR, California State Parks and US Park Service also broaden the scope of training and facilitate the transfer of information and skills between university researchers, government scientists and policy-makers.

所有生物在地理分布上都是有限的，但这些范围限制是如何以及为什么发生的，人们知之甚少。哪些生态过程在短期内强制实施范围限制，哪些遗传限制阻止自然选择在长期内实现范围扩大？这一缺陷阻碍了对物种在气候变化期间是否会改变活动范围或灭绝的现实预测，以及对濒临灭绝的加拿大物种的有效保护战略，这些濒危物种大多发生在加拿大，位于美国边境以南更广泛分布的北部边界。我的研究试图更好地理解范围界限的生态学和进化。**一个物种的分布被认为反映了它的生态位：在什么条件下生存和繁殖足以维持种群的可持续发展。一个物种没有出现的地区只是在它的生态位之外。然而，我们最近分析了衡量被移植物种超出其范围的性能的研究，发现在所有案例中，50%的物种范围限制与生态位限制不一致。不幸的是，很少有研究旨在提供明确的答案，因此显然需要更多的实验。物种的扩散能力也可能限制其分布，但这仍然是推测。我们将结合大规模地理调查、移植实验和对扩散的遗传估计，来测试生态位限制与扩散对范围限制的相对贡献。**范围限制的长期进化停滞被认为是因为范围边缘种群缺乏允许持续超过范围限制的特征的遗传变异，或者是因为来自更大种群的基因向范围中心的迁移持续阻碍了为提高在范围限制下的表现而进行的自然选择。我们将通过结合移植实验和基因运动的遗传分析以及边缘种群的适应潜力来检验这些假设。**地理范围边缘可能是重大进化的场所。例如，一些植物在繁殖过程中表现出惊人的边缘变化，通常涉及从有性繁殖到无性繁殖的转变。性的丧失和范围边缘的基因重组可能会降低进一步适应的可能性。另一方面，无性恋可以保护边缘环境中有利的基因的独特组合，使其不被重组所破坏。我们将通过比较中央和边缘生境中移植的有性和无性基因型的表现，以及测试范围边缘长期无性繁殖的基因组签名来评估这些假设。**这项研究将有助于回答生物学前沿的基本问题，并有助于保护稀有物种，管理外来入侵者，以及更好地预测物种对气候变化的反应；影响加拿大生物多样性的关键环境问题。我将与被证明是优秀的实验对象和实验技术的物种合作，我们已经成功地使用了这些物种。拟议的研究涉及一系列高度可转让的技术技能，包括现代遗传技术、不同生态系统的田间生物学、实验设计、高级统计分析和生物信息学。因此，它将为各级受训人员提供适合他们在学术界、资源管理和工业的不同兴趣和长期职业目标的研究经验和技能。与加拿大公园、安大略省MNR、加州州立公园和美国公园管理局正在进行的研究伙伴关系还扩大了培训范围，并促进了大学研究人员、政府科学家和政策制定者之间的信息和技能转移。