Data from: Parallel effects of the inversion In(3R)Payne on body size across the North American and Australian clines in Drosophila melanogaster

Chromosomal inversions are thought to play a major role in climatic adaptation. In D. melanogaster, the cosmopolitan inversion In(3R)Payne exhibits latitudinal clines on multiple continents. Since many fitness traits show similar clines, it is tempting to hypothesize that In(3R)P underlies observed clinal patterns for some of these traits. In support of this idea, previous work in Australian populations has demonstrated that In(3R)P affects body size but not development time or cold resistance. However, similar data from other clines of this inversion are largely lacking; finding parallel effects of In(3R)P across multiple clines would considerably strengthen the case for clinal selection. Here, we have analyzed the phenotypic effects of In(3R)P in populations originating from the endpoints of the latitudinal cline along the North American east coast. We measured development time, egg-to-adult survival, several size-related traits (femur and tibia length, wing area and shape), chill coma recovery, oxidative stress resistance and triglyceride content in homokaryon lines carrying In(3R)P or the standard arrangement. Our central finding is that the effects of In(3R)P along the North American cline match those observed in Australia: standard arrangement lines were larger than inverted lines, but the inversion did not influence development time or cold resistance. Similarly, In(3R)P did not affect egg-to-adult survival, oxidative stress resistance and lipid content. In(3R)P thus seems to specifically affect size traits in populations from both continents. This parallelism strongly suggests an adaptive pattern, whereby the inversion has captured alleles associated with growth regulation and clinal selection acts on size across both continents.

染色体倒位被认为在气候适应过程中发挥核心作用。在黑腹果蝇（D. melanogaster）中，广布型染色体倒位In(3R)Payne（下文简称In(3R)P）在多个大陆均呈现纬度渐变群格局。鉴于诸多适合度性状亦存在类似的渐变群模式，据此可合理提出如下假说：In(3R)P是部分这类性状渐变群格局的遗传基础。为支持这一假说，此前针对澳大利亚种群的研究已证实，In(3R)P可影响体型大小，但对发育时长与耐寒性无显著作用。然而，该倒位在其他渐变群中的同类研究数据仍较为匮乏；若能证实In(3R)P在多个渐变群中存在平行效应，将极大强化渐变群选择假说的佐证力度。

本研究针对北美东海岸纬度渐变群两端的种群，分析了In(3R)P的表型效应。我们对携带In(3R)P倒位或标准染色体构型的纯合核型品系，测定了如下指标：发育时长、卵到成虫存活率、多项体型相关性状（股骨与胫骨长度、翅面积及翅形）、冷昏迷恢复时长、抗氧化应激能力以及甘油三酯含量。

本研究的核心发现为：In(3R)P在北美渐变群中的效应与澳大利亚种群的观测结果高度一致——标准构型品系的体型大于倒位型品系，但该倒位对发育时长与耐寒性并无影响。此外，In(3R)P对卵到成虫存活率、抗氧化应激能力以及脂质含量均无显著作用。由此可见，In(3R)P似乎仅在两大洲的种群中特异性影响体型相关性状。这种平行效应强烈表明存在一种适应性进化模式：该倒位捕获了与生长调控相关的等位基因，且两大洲的渐变群选择均对体型性状施加了选择压力。