Data from: Investigating yellow dung fly body size evolution in the field: response to climate change?

Uncovering genetic responses to selection in wild populations typically requires tracking individuals over generations and use of animal models. Our group monitored the body size of one Swiss Yellow Dung Fly (Scathophaga stercoraria; Diptera: Scathophagidae) field population over 15 years, including intermittent common garden rearing in the laboratory to assess body size with minimized environmental and maximized genetic variation. Contrary to expectations based on repeated heritability and phenotypic selection assessments over the years (reported elsewhere), field body sizes declined by >10% and common-garden laboratory sizes by >5% from 1993 – 2009. Our results confirm the temperature-size rule (smaller when warmer) and, albeit entirely correlational, could be mediated by climate change, as over this period mean temperature at the site increased by 0.5 °C, although alternative systematic environmental changes cannot be entirely excluded. Monitoring genetic responses to selection in wild invertebrate populations is thus possible, though indirect, and wild populations may evolve in directions not consistent with strongly positive directional selection favoring large body size.揭示野生种群对选择的遗传响应，通常需要跨世代追踪个体并应用动物模型（animal model）。本研究团队对一个瑞士黄粪蝇（Swiss Yellow Dung Fly，*Scathophaga stercoraria*；双翅目：粪蝇科）的野外种群开展了长达15年的体型监测，期间间歇性开展实验室同质园饲养（common garden rearing）实验，以在最小化环境差异、最大化遗传变异的条件下评估个体体型。与此前基于多年重复遗传力（heritability）与表型选择（phenotypic selection）评估（已在其他文献发表）得出的预期相悖，1993至2009年间，野外种群的体型下降幅度超过10%，实验室同质园饲养个体的体型下降幅度亦超过5%。本研究结果证实了温度-体型规则（temperature-size rule，即温度越高个体体型越小）；尽管本研究的结论完全基于相关性分析，但该结果可能由气候变化介导——研究期间该样地的平均气温上升了0.5℃，不过我们无法完全排除其他系统性环境变化的潜在影响。因此，尽管属于间接监测，但在野生无脊椎动物种群中开展选择的遗传响应监测是可行的；且野生种群的演化方向可能并不符合“青睐大体型的强正向定向选择（directional selection）”这一预设。