Data from: Altitudinal clinal variation in wing form in African Drosophila melanogaster: one cline or many?

Geographical patterns of morphological variation have been useful in addressing hypotheses about environmental adaptation. In particular, latitudinal clines in phenotypes have been studied in a number of Drosophila species. Some environmental conditions along latitudinal clines—for example, temperature—also vary along altitudinal clines, but these have been studied infrequently and it remains unclear whether these environmental factors are similar enough for convergence or parallel evolution. Most clinal studies in Drosophila have dealt exclusively with univariate phenotypes, allowing for the detection of clinal relationships, but not for estimating the directions of covariation between them. We measured variation in wing shape and size in D. melanogaster derived from populations at varying altitudes and latitudes across sub-Saharan Africa. Geometric morphometrics allows us to compare shape changes associated with latitude and altitude, and manipulating rearing temperature allows us to quantify the extent to which thermal plasticity recapitulates clinal effects. Comparing effect vectors demonstrates that altitude, latitude, and temperature are only partly associated, and that the altitudinal shape effect may differ between Eastern and Western Africa. Our results suggest that selection responsible for these phenotypic clines may be more complex than just thermal adaptation.

形态变异的地理分布模式，在验证环境适应性相关假说方面具有重要应用价值。具体而言，诸多果蝇（Drosophila）物种的表型纬度梯度变异已被广泛研究。沿纬度梯度分布的部分环境条件（例如温度），同样会随海拔梯度发生变化，但此类研究较为匮乏，目前仍不清楚这些环境因素的相似性是否足以促成趋同演化或平行演化。绝大多数果蝇的梯度变异研究仅针对单变量表型，仅能检测到梯度变异关联，却无法估算二者间的协变方向。本研究对撒哈拉以南非洲不同海拔与纬度种群的黑腹果蝇（Drosophila melanogaster）翅形与翅大小变异进行了测定。借助几何形态测量学（Geometric morphometrics），我们可对比与纬度、海拔相关的翅形变化；通过调控饲养温度，我们能够量化温度可塑性重现梯度变异效应的程度。通过对比效应向量可知，海拔、纬度与温度仅存在部分关联，且非洲东西部的海拔诱导翅形效应可能存在差异。本研究结果表明，驱动这些表型梯度变异的选择压力，可能远比单纯的温度适应更为复杂。