Fine-scale local adaptation in life histories along a continuous environmental gradient in Trinidadian guppies
Fine-scale local adaptation in life histories along a continuous environmental gradient in Trinidadian guppies
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DOI：
10.1111/j.1365-2435.2012.01980.x
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发表时间：
2012-06-01
影响因子：
5.2
通讯作者：
Ghalambor, Cameron K.
中科院分区：
文献类型：
--
作者：
Torres-Dowdall, Julian;Handelsman, Corey A.;Ghalambor, Cameron K.
1. 生命史进化的理论模型预测了从快到慢的生命史的连续性，但这一理论的大多数实证支持来自考虑二分环境的研究（即高食物与低食物、存在或不存在主要捕食者）。尽管这种方法在识别局部适应的特征方面非常成功，但它可能会限制我们识别表型变异的潜在模式原因的能力。通过研究生活史特征沿连续梯度的变化，我们可以更好地了解自然种群表现出的适应多样性。 2. 我们研究了特立尼达孔雀鱼（Poecilia reticulata）生活史特征沿着捕食压力梯度的演变。根据捕食者群落，选择了瓜纳波卡罗尼河流域沿线的六个地点，从孔雀鱼仅与单一张口限制鱼类捕食者共存的上游地区，到孔雀鱼与复杂鱼类群落共存的低地地区。沿着这个梯度，我们描述了成熟时年龄和大小以及繁殖努力的表型变异的现场模式。此外，为了确定这种变异的遗传基础，我们测量了来自同一地点的野生采样的第二代实验室出生的鱼的这些特征。 3. 在自然界中，我们在大多数生活史特征中发现了与连续捕食梯度平行的精细表型变异模式。在实验室中，我们观察到，随着捕食者群落的减少，生殖分配和孵化规模逐渐减小，而成熟年龄和孵化间隔逐渐增加，这表明在野外观察到的生殖分配和后代数量的平行模式具有遗传基础。 4. 然而，观察到的变化模式也存在一些例外情况。由于鱼类群落的简单性质，来自低捕食地区的雌性成熟得更早，繁殖也比预期的更频繁。我们还发现我们的现场结果和实验室结果之间的胚胎大小存在显着差异，表明这一性状具有高度可塑性。 5. 我们的结果表明孔雀鱼的局部适应比之前显示的更精细。此外，虽然我们的结果与捕食者驱动的生活史变异一致，但我们还发现了传统二分法中不明显的可塑性模式。
1. Theoretical models of life-history evolution predict a continuum of fast to slow life histories, yet most of empirical support for this theory comes from studies that have considered dichotomous environments (i.e. high vs. low food, presence or absence of major predators). Although this approach has been very successful in identifying the signature of local adaptation, it might limit our ability to identify the causes of underlying patterns of phenotypic variation. By studying the variation in life-history traits along continuous gradients, we can gain better insight into the diversity of adaptations exhibited by natural populations. 2. We studied the evolution of life-history traits along a gradient of predation pressure in the Trinidadian guppy (Poecilia reticulata). Six localities along the GuanapoCaroni River drainage were selected with respect to their predator community, going from upstream localities where guppies only coexist with a single gape-limited fish predator, to lowland sites where guppies coexist with a complex fish community. Along this gradient, we characterized the field pattern of phenotypic variation in age and size at maturity and reproductive effort. Further, to determine the genetic basis of this variation, we measured these traits in second-generation laboratory-born fish from the same localities sampled in the wild. 3. In nature, we found a fine-scale pattern of phenotypic variation in most life-history traits that paralleled the continuous predation gradient. In the laboratory, we observed that reproductive allocation and brood size progressively decrease while age at maturity and interbrood interval progressively increase with a reduction in the predator community, suggesting a genetic basis to the parallel patterns observed in the field for reproductive allocation and offspring number. 4. However, there were some exceptions to the observed pattern of variation. Females from one low-predation locality matured younger and reproduced more frequently than expected based upon the simple nature of the fish community. We also found significant differences between our field and laboratory results for embryo size, suggesting that this trait is highly plastic. 5. Our results imply that local adaptation in guppies occurs at a finer scale than has previously been shown. Furthermore, while our results are consistent with predator-driven life-history variation, we also find patterns of plasticity that would not be apparent in the traditional dichotomous approach.