Organisms are locally adapted when members of a population have a fitness advantage in one location relative to conspecifics in other geographies. For example, across latitudinal gradients, some organisms may trade off between traits that maximize fitness components in one, but not both, of somatic maintenance or reproductive output. Latitudinal gradients in life history strategies are traditionally attributed to environmental selection on an animal's genotype, without any consideration of the possible impact of associated microorganisms ("microbiota") on life history traits. Here, we show in Drosophila melanogaster, a key model for studying local adaptation and life history strategy, that excluding the microbiota from definitions of local adaptation is a major shortfall. First, we reveal that an isogenic fly line reared with different bacteria varies the investment in early reproduction versus somatic maintenance. Next, we show that in wild fruit flies, the abundance of these same bacteria was correlated with the latitude and life history strategy of the flies, suggesting geographic specificity of the microbiota composition. Variation in microbiota composition of locally adapted D. melanogaster could be attributed to both the wild environment and host genetic selection. Finally, by eliminating or manipulating the microbiota of fly lines collected across a latitudinal gradient, we reveal that host genotype contributes to latitude-specific life history traits independent of the microbiota and that variation in the microbiota can suppress or reverse the differences between locally adapted fly lines. Together, these findings establish the microbiota composition of a model animal as an essential consideration in local adaptation.

中文翻译：

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微生物群影响果蝇的生活史策略。

当人口成员相对于其他地区的物种在某个位置具有健身优势时，就可以对有机体进行局部适应。例如，在整个纬度梯度上，某些生物可能会在使躯体维持或生殖输出中的一种（而不是两者）最大化适应性的性状之间进行权衡。传统上，生命史策略中的纬度梯度归因于对动物基因型的环境选择，而不考虑相关微生物（“微生物群”）对生命史特征的可能影响。在这里，我们在果蝇（Drosophila melanogaster）中显示了一种研究局部适应和生活史策略的关键模型，认为将微生物群从局部适应的定义中排除是一个重大的不足。第一的，我们揭示了用不同细菌饲养的等基因蝇系会改变早期繁殖与体细胞维持的投资。接下来，我们表明在野生果蝇中，这些相同细菌的丰度与果蝇的纬度和生活史策略相关，这表明了微生物群组成的地理特异性。适应当地的D. melanogaster的微生物群组成的变化可归因于野生环境和宿主遗传选择。最后，通过消除或操纵跨横向梯度收集的蝇系的微生物区系，我们揭示了宿主基因型有助于独立于微生物群的纬度特定的生活史特征，并且微生物区系的变化可以抑制或逆转局部适应的蝇系之间的差异。线。一起，