Individual and Population Responses to Environmental Change: Allee Effects, Phenotypic Plasticity, and Life History in Fishes

生活史理论为理解个体和群体对自然和人为环境变化的反应提供了解释性和预测性框架。通过影响生育成功，生活史影响适合度；通过影响适合度，生活史影响人口统计。我们预测生理、生活史、人口统计和进化对环境变化的反应的能力的不确定性，破坏了对生活史变化的原因和后果的全面理解。正是这些不确定性刺激了我的长期目标，即通过确定环境变化如何影响健康，来探索种群内和种群间变异性在生活史上的适应意义。我的短期目标是从以下几个方面洞察个人和群体对环境变化的反应的适应性意义：i)Allee效应；(Ii)反应规范；(Iii)制度变化；以及(Iv)生态变异。小人口动态的组成部分是Allee效应--丰度(或密度)与实现的人均人口增长之间的正向关系。下降的幅度越大，发生Allee效应的可能性就越大，从而对健康和恢复产生负面影响。最近的密度依赖选择模型强调了快速进化的重要性，这是一种“进化拯救”形式。然而，直接证据是有限的。通过对日本青竹的实验室选择实验，我将检验人口统计和新出现的Allee效应是否会在小种群和不同的复苏轨迹中产生不同的选择反应。生活史随着环境条件的均值和方差的变化而演变。然而，研究几乎完全集中在平均温度的变化上，而不是热变率的变化上，这限制了人们对热变异性如何独立于平均温度的方向性变化影响适合度的理解。基于对斑马鱼的实验，我问可塑性(发育和跨代)和温度波动如何影响适应性、抗热震性和对低氧环境的耐受性。环境变化影响生物多样性。许多模型对物种将如何应对全球变化进行了预测性分析，但很少有预测得到证实。使用贝叶斯变点检测算法，我将通过对超长(长达100年)的数据集进行区域变化分析，确定人为和自然“压力源”如何影响沿海鱼类生物多样性。在生物多样性的种内水平上，我将探索环境变化如何影响大西洋鳕鱼遗传上不同生态型的比例代表，并测试生态型是由足以对杂交概率或杂交后代存活产生负面影响的实质性因素维持的假设。

Life-history theory offers explanatory and predictive frameworks for understanding individual and population responses to natural and anthropogenic environmental change. By affecting reproductive success, life histories affect fitness; by affecting fitness, life histories affect population demography. Comprehensive understanding of the causes and consequences of life-history variation is undermined by uncertainties in our ability to predict physiological, life history, demographic, and evolutionary responses to environmental change. It is these uncertainties that stimulate my long-term objective to explore the adaptive significance of within- and among-population variability in life history, by determining how environmental change influences fitness. My short-term objective is to gain insight into the adaptive significance of individual and population responses to environmental change in light of: i) Allee effects; (ii) reaction norms; (iii) regime shifts; and (iv) ecotypic variation. Integral to the dynamics of small populations are Allee effects - positive relationships between abundance (or density) and realized per capita population growth. The greater the magnitude of decline, the greater the likelihood of Allee effects, negatively affecting fitness and recovery. Recent models of density-dependent selection emphasize the importance of rapid evolution, a form of `evolutionary rescue'. However, direct evidence is limited. Using laboratory-based selection experiments on Japanese medaka, I will examine whether demographic and emergent Allee effects generate different selection responses in small populations and different recovery trajectories. Life histories evolve in response to changes in the mean and variance of environmental conditions. However, research has focused almost exclusively on shifts in average temperature rather than shifts in thermal variability, limiting understanding of how thermal variability affects fitness independently of directional changes in mean temperature. Based on experiments on zebrafish, I ask how plasticity (developmental & transgenerational) and thermal fluctuations affect fitness, resistance to heat shock, and tolerance to low-oxygen environments. Environmental change affects biodiversity. Numerous models have generated predictive analyses of how species will respond to global change but few predictions have been ground-truthed. Using a Bayesian change-point detection algorithm, I will determine how anthropogenic and natural `stressors' have affected coastal fish biodiversity, by applying regime-shift analyses to exceptionally long (up to 100 years) datasets. At the intra-specific level of biodiversity, I will explore how environmental change influences the proportional representation of genetically different ecotypes in Atlantic cod, and test the hypothesis that ecotypes are maintained by factors substantive enough to negatively affect the probability of interbreeding or the survival of hybrid offspring.