Ecology & Evolution of Species Range Limits

所有的生物在地理分布上都是有限的，但是范围限制是如何以及为什么发生的，人们仍然知之甚少。这阻碍了对物种是否会在气候变化期间迁移或灭绝的现实预测，并削弱了对加拿大濒危物种的有效保护，其中大多数物种位于加拿大南部的北部边界。我的研究目标是更好地理解生态和进化过程，这些过程在短期内限制了范围，并在长期内阻止了范围的扩大。我和我的学生将通过填补以下描述的4个知识空白来实现这一目标，每一个空白都是距离限制难题的缺失部分。范围限制被认为发生在环境使生存和繁殖减少到足以使种群不能自我替换的地方。虽然移植到其活动范围以外的物种经常遭受损失，但它们的性能下降往往不足以限制分布。在这种情况下，扩散可能是有限的，但如何发生尚不清楚。一种可能但未经验证的假设是，当一个物种向无人居住的栖息地扩散的速度跟不上其从已占据的栖息地灭绝的速度时，就会出现范围限制。(2)在其分布范围内，一个物种可能出现在多种生境中，所占生境的范围可能向范围极限缩小。反过来，这可能会减少物种持续生存所需的栖息地斑块之间的成功扩散。然而，很少研究生境宽度是否在牧地边缘发生变化，其潜在机制也不清楚。(3)稳定范围限制被认为发生在适应失败的地方。最近的实验未能揭示适应的必要限制，但没有一个研究在自然条件下多代的适应。(4)外围种群对范围外条件的适应能力将受到繁殖方式的强烈影响。植物经常将繁殖模式转向范围限制，但这是否会抑制或促进地理传播尚不清楚。我们通过大规模的地理调查、操纵移植实验和基因组分析来解决这些目标，这些分析与植物物种被证明是优秀的实验系统。这项研究将有助于回答生物学前沿的基本问题，并有助于濒危物种的保护、外来入侵者的管理，以及更好地预测物种对气候变化的反应；威胁加拿大生物多样性的关键环境问题。我的实验室是一个包容的环境，在这里，不同层次的学员学习高度可转移的技术技能，适合他们在学术界、资源管理和行业的兴趣和长期职业目标。与资源管理机构的持续伙伴关系扩大了培训并促进了大学研究人员、政府科学家和决策者之间的信息和技能转让。

All organisms are limited in geographic distribution, but how & why range limits occur are still poorly understood. This prevents realistic forecasting of whether species will shift ranges or go extinct during climate change and weakens effective conservation of Canadian species at risk most of which are at their northern limits in southern Canada. The goal of my research is to better understand the ecological and evolutionary processes that impose range limits over the short-term and prevent range expansion over the long term. My students and I will address this goal by filling 4 knowledge gaps described below, each of which is a missing piece of the range-limit puzzle. (1) A range limit is thought to occur where the environment reduces survival and reproduction sufficiently that populations are not self-replacing. Although species transplanted beyond their range often suffer, their reduced performance is often insufficient to limit the distribution. In such cases, dispersal may be limiting but how this occurs is unknown. A likely but untested hypothesis is that the range limit occurs where a species' dispersal into unoccupied habitat patches fails to keep pace with its extinction from occupied patches. (2) Across its range, a species may occur in a variety of habitats and the range of habitats occupied may narrow towards range limits. This may, in turn, reduce successful dispersal between habitat patches required for species persistence. However, whether habitat breadth changes at range edges has rarely been studied and underlying mechanisms are not understood. (3) Stable range limits are thought to occur where adaptation fails. Recent experiments have failed to reveal the necessary constraints on adaptation, but none have examined adaptation over multiple generations under natural conditions. (4) The capacity of peripheral populations to adapt to conditions beyond the range will be strongly influenced by reproductive mode. Plants often shift reproductive modes towards range limits, but whether this inhibits or facilitates geographic spread is unknown. We address these objectives using large-scale geographic surveys, manipulative transplant experiments and genomic analyses with plants species proven to be excellent experimental systems. This research will help answer fundamental questions at the forefront of biology and contribute to the conservation of species-at-risk, the management of exotic invaders, and better forecasting of species' responses to climate change; key environmental problems threatening Canadian biodiversity. My lab is an inclusive environment where diverse trainees at all levels learn highly transferable technical skills suited to their interests and long-term career goals in academia, resource management and industry. Ongoing partnerships with resource-management agencies broaden training and facilitate the transfer of information and skills between university researchers, government scientists and policy-makers.