Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT, USA.
Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.
Mol Ecol. 2020 Feb;29(3):639-653. doi: 10.1111/mec.15344. Epub 2020 Jan 3.
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.
当一个种群的成员在一个地点相对于其他地理区域的同种个体具有适应性优势时，它们就是局部适应的。例如，在纬度梯度上，一些生物可能会在最大限度地提高一个适应性成分的特征与最大限度地提高另一个适应性成分的特征之间进行权衡，而这两个适应性成分在躯体维持或生殖输出方面并不完全一致。生命史策略的纬度梯度传统上归因于对动物基因型的环境选择，而没有考虑相关微生物（“微生物组”）对生命史特征的可能影响。在这里，我们在黑腹果蝇中展示了这一点，黑腹果蝇是研究局部适应和生命史策略的重要模型生物，将微生物组排除在局部适应的定义之外是一个主要的缺陷。首先，我们揭示了在不同细菌中培养的同基因系会改变早期繁殖与躯体维持之间的投入。其次，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命史策略相关，这表明了微生物组组成的地理特异性。局部适应的黑腹果蝇的微生物组组成的变化可能归因于野生环境和宿主遗传选择。最后，通过消除或操纵在纬度梯度上收集的蝇线的微生物组，我们揭示了宿主基因型独立于微生物组对特定于纬度的生命史特征的贡献，并且微生物组的变化可以抑制或逆转局部适应的蝇线之间的差异。总之，这些发现确立了模型动物的微生物组组成是局部适应的一个重要考虑因素。
