Community response to environmental change: the role of dispersal, local adaptation, and species interactions

由于广泛的干扰，水生生态系统正在经历前所未有的变化。最严重的影响之一是生物多样性的下降，这通常会导致物种相互作用、能量流和生物量生产的改变。虽然我们通常对环境压力源对单个物种的直接影响有很好的了解，但我们对群落层面的影响普遍了解甚少，因为间接影响发生在地方和区域范围内。 如果在新条件下生存和繁殖受到损害，敏感物种或基因型可能会被灭绝。 如果有个体具有能够在新环境中繁衍生息的特征，其他物种/基因型可能能够适应改变的环境条件。 这些个体可能已经存在于当地环境中，或者他们可能来自该地区的其他栖息地。 *在过去的几十年里，生态学家已经认识到生物在栖息地之间的移动可以塑造当地的群落组成。 然而，影响当地过程与扩散的相对重要性的因素尚不清楚，特别是对于面临环境变化的社区。 例如，如果当地社区迅速适应新条件并垄断资源，高度的当地多样性可能会减少区域物种库分散者的影响，从而阻止到达物种的建立。 或者，干扰可能会减少当地的丰度，减轻物种相互作用的强度并促进分散物种的建立。 最后，到达物种的数量、频率和多样性可能会影响它们的定居能力。*了解群落反应的挑战与广泛的水生应激源有关，但区域性钙下降可以说是加拿大地盾上数千个湖泊面临的最紧迫但未被充分研究的威胁之一。 与伐木相关的区域酸化和生物量去除导致土壤和水体缺钙。 湖泊中主要富含钙的食草动物的减少与水中钙浓度的降低有关。尽管如此，旨在了解低钙浓度对社区水平影响的研究仍然很少。*我建议结合实验室和现场实验来解决以下问题：1）是否有证据表明当地有适应环境变化的能力？ 2）环境变化如何影响物种相互作用（竞争和捕食）的强度以及随后区域分散者的建立？ 3) 扩散特征如何影响区域物种库中的物种在当地受干扰环境中的建立？ 对于该提案的第四个组成部分，我们将确定评估我们的实验中揭示的机制使用景观尺度物种分布解释自然模式的程度。 *这项研究将通过增加我们对社区对环境变化的反应的了解，特别是钙浓度的广泛下降，使加拿大受益。 这些信息将引导湖泊管理者和政策制定者关注针对湖泊的具体行动，以保护当地生物多样性或区域规模的努力，以维持区域多样性和湖泊连通性。 4 名博士生、1 名硕士生和至少 13 名理学士生将接受现场生物学、实验设计、统计分析和交流方面的培训。 这些是环境领域备受追捧的技能，但也可以转移到需要批判性思维、定量技能、沟通和强有力的领导力的其他职业。

Aquatic ecosystems are experiencing unprecedented change owing to a wide range of disturbances. One of the most serious repercussions is a decline in biodiversity, which often results in altered species interactions, energy flow, and biomass production. While we often have a good understanding of direct effects of environmental stressors on individual species, we have a generally poor understanding of the community-level effects because of indirect effects occurring at both a local and regional scale. Sensitive species or genotypes may be extirpated if survival and reproduction is impaired under the new conditions. Other species/genotypes may be able to adapt to altered environmental conditions if there are individuals with traits enabling them to flourish in the new environment. These individuals may already be present in the local environment or they may arrive from other habitats in the region. *Over the past several decades, ecologists have recognized that the movement of organisms between habitats can shape local community composition. However, factors that influence the relative importance of local processes versus dispersal are not well understood, particularly for communities facing environmental change. For example, high local diversity may reduce the influence of dispersers from the regional species pool if local communities quickly adapt to the new conditions and monopolize resources, thereby preventing the establishment of arriving species. Alternatively, the disturbance may reduce local abundances, lessening the intensity of species interactions and facilitating establishment of dispersing species. Finally, the number, frequency, and diversity of arriving species may influence their ability to establish.*The challenge of understanding community response is relevant to a wide range of aquatic stressors, but regional calcium-decline is arguably one of the most pressing but understudied threats facing thousands of lakes on the Canadian Shield. Regional acidification and biomass removal associated with logging have resulted in calcium-depleted soils and water bodies. Declines in key calcium-rich herbivores in lakes have been linked with reduced aqueous calcium concentrations. Despite this, there is a paucity of studies aimed at understanding community-level effects of low calcium concentrations.*I propose to use a combination of laboratory and field experiments to address the following questions: 1) Is there evidence of local adaptation in response to environmental change? 2) How does environmental change influence the strength of species interactions (competition & predation) and subsequent establishment of regional dispersers? and 3) How do characteristics of dispersal influence probably that species from the regional species pool will establish in local disturbed environments? For the fourth component of the proposal, we will determine evaluate the extent to which mechanisms revealed in our experiments explain patterns in nature using landscape-scale species distributions. *This research will benefit Canada by increasing our understanding of community response to environmental change, in particular, wide spread decline of calcium concentration. This information will direct the focus of lake managers and policy-makers to lake-specific actions for preserving local biodiversity or regional-scale efforts for maintaining regional diversity and lake-connectivity. Four PhD, 1 MSc, and at least 13 BSc students will be trained in field biology, experimental design, statistical analyses, and communication. These are highly sought skills in environmental fields, but also transfer to other careers that require critical thinking, quantitative skills, communication, and strong leadership.