Collaborative Research: The Evolutionary Interplay between Life Histories, Morphologies, Performance, and Behavior in Trinidad Guppies

自然选择的进化，或适应原则，是查尔斯·达尔文提出的进化机制。达尔文认为适应是生物体的任何特征，是自然选择的结果，增强了个体的生存和繁殖潜力。然而，理解和实证记录一个特定的特征之间的关系，似乎是适应性和因素选择的特征的进化仍然是一个具有挑战性和争议的任务。自达尔文以来，从自然选择的实证研究中得到的主要教训是，适应很少孤立地发生，而是受到其他相互作用的特征的功能的限制，最终是有机体的综合方面之间的妥协。因此，适应性的研究需要了解不同的性状如何相互制约，以及它们如何整合以产生局部适应的表型。只有有限的经验证据表明这些限制是如何在真实的生物体中表现出来的。本研究将研究孔雀鱼（Poecilia reticulata）自然种群的生殖策略、体型、游泳表现和行为的整合如何受到选择的影响。孔雀鱼是这项研究的模式生物，因为它是为数不多的有适应记录的生物之一。这项先前的工作表明，孔雀鱼的生殖特征在对掠食性鱼类的反应中发生了快速的适应性变化。本文首先通过对不同选择压力的雌、雄孔雀鱼种群的野外观察，记录了生殖性状、身体形态、栖息地利用、觅食行为和溪流类型之间的相关性。它将侧重于水流和捕食的综合影响。由于孔雀鱼的生殖特征已经从这些地点得知，形态学和行为学的结果将提供关于身体形态、觅食行为、栖息地利用和生殖策略是否可预测地相互协同变化，或者它们是否在不同的选择压力下独立变化的第一个数据。然后将在实验室中在不同的环境下饲养孔雀鱼，以测试种群之间的这些性状差异在多大程度上代表了固定的遗传差异或表型可塑性。最后，本研究将首次研究怀孕对水生物种身体形态和运动的影响，通过测量身体轮廓和游泳表现在生殖周期中的变化。从高掠食区和低掠食区雌鱼的稳定和逃逸游泳表现将检验不同生殖分配对运动的影响，以及后代数量的适应性变化如何影响运动。通过研究生殖策略、形态、运动表现和行为如何相互作用，并共同应对不同的选择压力，本研究将更好地理解活鱼适应当地环境所面临的权衡。

Evolution by natural selection, or the principle of adaptation, was Charles Darwin's proposed mechanism for evolution. Darwin viewed an adaptation as any feature of an organism that arose as consequence of natural selection and enhanced the survival and reproductive potential of the individual. Yet, understanding and empirically documenting the relationship between a particular trait that appears to be adaptive and the factors that selected for the evolution of the trait remains a challenging and controversial task. In the time since Darwin, the main lessons learned from empirical studies of natural selection are that adaptations rarely occur in isolation, but rather are constrained by the function of other interacting traits, and are a ultimately a compromise between integrated aspects of the organism. Accordingly, the study of adaptation requires an understanding of how different traits constrain each other and how they are integrated to produce locally adapted phenotypes. There is only limited empirical evidence for how such constraints are manifested in real organisms. The proposed work will examine how selection acts on the integration of reproductive strategies, body shape, swimming performance, and behavior in natural populations of the guppy, Poecilia reticulata. The guppy is a model organism for the proposed work because it is one of the few organisms where adaptation has been documented. This previous work shows rapid adaptive changes in the reproductive traits of guppies in response to predatory fish. The work proposed here will first document the correlations among reproductive traits, body morphology, habitat use, foraging behavior, and stream type with field observations on female and male guppies from populations that are subject to different selection pressures. It will focus on the combined influences of stream current and predation. Because the reproductive traits of guppies are already known from these sites, the morphological and behavioral results obtained will provide the first data on whether body morphology, foraging behavior, habitat use, and reproductive strategies predictably covary with each other, or whether they vary independently in response to different selection pressures. Guppies will then be reared in the lab under different environments to test the degree to which these trait differences between populations represent fixed genetic differences or phenotypic plasticity. Finally, the proposed work will examine for the first time the consequences of pregnancy on body morphology and locomotion in an aquatic species by measuring how body profile and swimming performance change over the course of the reproductive cycle. Steady and escape swimming performance of gravid females from high and low predation localities will test the consequences of different reproductive allotments on locomotion and how adaptive changes in offspring number may compromise locomotion. By studying how reproductive strategies, morphology, locomotor performance, and behavior interact with each other and collectively respond to different selection pressures, the proposed work will provide a better understanding of the trade-offs faced by live-bearing fish adapting to their local environments.