Potential Mechanisms Driving Population Variation in Spatial Memory and the Hippocampus in Food-caching Chickadees
Potential Mechanisms Driving Population Variation in Spatial Memory and the Hippocampus in Food-caching Chickadees
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DOI：
10.1093/icb/icv029
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发表时间：
2015-09-01
影响因子：
2.6
通讯作者：
Pravosudov, Vladimir V.
中科院分区：
文献类型：
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作者：
Croston, Rebecca;Branch, Carrie L.;Pravosudov, Vladimir V.
据推测，恶劣的环境和严冬有利于提高成功觅食所需的认知能力。那么，冬季气候的地理变化可能与认知能力选择压力的差异有关，假设这些性状的变异是可遗传的，这可能会导致认知及其神经机制的进化变化。在这里，我们重点关注两种储存食物的山雀（Poecile 属），它们依靠储存的食物过冬，并需要使用空间记忆来恢复储存的食物。这些物种在空间记忆和海马体中也表现出与气候相关的广泛种群水平变化，包括体积、神经元总数和大小以及成虫的神经发生率。这种变异可能是由自然选择背景下的多种机制驱动的，包括独立的、特定人群的选择（局部适应）、基于环境经验的可塑性、发育差异和/或表观遗传差异。关于这两种山雀的多个种群在冬季气候中沿纵向、纬度和海拔梯度的认知、大脑形态和行为的大量数据与自然选择驱动与种群间空间记忆差异相关的局部适应进化的假设最为一致。相反，环境引起的可塑性或发育差异是跨气候梯度人口差异的主要原因的假设几乎没有支持。关于记忆能力表观遗传修饰的现有数据也与观察到的种群变异模式不一致，生活在压力更大和更恶劣环境中的鸟类具有更好的空间记忆，这与更大的海马体和更多数量的海马神经元相关。总体而言，现有数据与以下假设最为一致：冬季气候的高度可预测差异通过局部适应，推动了种群间认知和大脑差异的进化和维持，至少在储存食物的鸟类中是如此。
Harsh environments and severe winters have been hypothesized to favor improvement of the cognitive abilities necessary for successful foraging. Geographic variation in winter climate, then, is likely associated with differences in selection pressures on cognitive ability, which could lead to evolutionary changes in cognition and its neural mechanisms, assuming that variation in these traits is heritable. Here, we focus on two species of food-caching chickadees (genus Poecile), which rely on stored food for survival over winter and require the use of spatial memory to recover their stores. These species also exhibit extensive climate-related population level variation in spatial memory and the hippocampus, including volume, the total number and size of neurons, and adults' rates of neurogenesis. Such variation could be driven by several mechanisms within the context of natural selection, including independent, population-specific selection (local adaptation), environment experience-based plasticity, developmental differences, and/or epigenetic differences. Extensive data on cognition, brain morphology, and behavior in multiple populations of these two species of chickadees along longitudinal, latitudinal, and elevational gradients in winter climate are most consistent with the hypothesis that natural selection drives the evolution of local adaptations associated with spatial memory differences among populations. Conversely, there is little support for the hypotheses that environment-induced plasticity or developmental differences are the main causes of population differences across climatic gradients. Available data on epigenetic modifications of memory ability are also inconsistent with the observed patterns of population variation, with birds living in more stressful and harsher environments having better spatial memory associated with a larger hippocampus and a larger number of hippocampal neurons. Overall, the existing data are most consistent with the hypothesis that highly predictable differences in winter climate drive the evolution and maintenance of differences among populations both in cognition and in the brain via local adaptations, at least in food-caching parids.