A fundamental aspect of evolutionary biology is natural selection on trait variation. Classically, selection has been estimated primarily on external morphological traits such as beak size and coloration, or on easily assayable physiological traits such as heat-tolerance. As technologies and methods improved, evolutionary biologists began examining selection on molecular traits such as protein sequences and cellular processes. In a From the Cover paper in this issue of Molecular Ecology, Ahmad et al. continue this trend by estimating parasite-driven selection on the molecular trait of transcript abundance in a wild population of brown trout (Salmo trutta) by uniquely combining a mark–recapture experimental design with noninvasive RNA sampling. Using transcript abundance to estimate selection allows for many different traits (each unique gene's transcript counts) to be tested in a single experiment, providing the opportunity to examine trends in selection. Ahmad et al. find directional selection strength on transcript counts is generally low and normally distributed. Surprisingly, transcripts under nonlinear selection showed a disruptive selection bias, contradicting previous comparative studies and theoretical work. This highlights the importance of within-generation selection studies, where mechanisms may differ from longer time frames. Their paper also highlights the benefits of a cost-effective 3′ RNA sequencing technique to measure gene expression.

中文翻译：

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创新的标记-重新捕获实验显示了野外转录本丰度的选择模式

进化生物学的一个基本方面是对性状变异的自然选择。传统上，主要根据外部形态特征（例如喙的大小和颜色）或易于测定的生理特征（例如耐热性）来估计选择。随着技术和方法的改进，进化生物学家开始研究对蛋白质序列和细胞过程等分子特征的选择。在本期《分子生态学》的封面论文中，Ahmad等人。通过估计野生褐鳟鱼（Salmo trutta）转录本丰度的分子特征的寄生虫驱动选择来延续这一趋势) 通过将标记-重新捕获实验设计与非侵入性 RNA 采样独特地结合起来。使用转录本丰度来估计选择允许在单个实验中测试许多不同的性状（每个独特基因的转录本计数），提供检查选择趋势的机会。艾哈迈德等人。发现转录本计数的定向选择强度通常较低且呈正态分布。令人惊讶的是，非线性选择下的转录本表现出破坏性的选择偏差，这与之前的比较研究和理论工作相矛盾。这突出了代内选择研究的重要性，其中机制可能与更长的时间框架不同。他们的论文还强调了一种具有成本效益的 3' RNA 测序技术来测量基因表达的好处。