Data from: Geographic clines in wing morphology relate to colonization history in New World but not Old World populations of yellow dung flies

Geographic clines offer insights about putative targets and agents of
natural selection as well as tempo and mode of adaptation. However,
demographic processes can lead to clines that are indistinguishable from
adaptive divergence. Using the widespread yellow dung fly Scathophaga
stercoraria (Diptera: Scathophagidae), we examine quantitative genetic
differentiation (QST) of wing shape across North America, Europe and
Japan, and compare this differentiation with that of ten microsatellites
(FST). Morphometric analyses of 28 populations reared at three
temperatures revealed significant thermal plasticity, sexual dimorphism
and geographic differentiation in wing shape. In North America
morphological differentiation followed the decline in microsatellite
variability along the presumed route of recent colonization from the
southeast to the northwest. Across Europe, where S. stercoraria presumably
existed for much longer time and where no molecular pattern of isolation
by distance was evident, clinal variation was less pronounced despite
significant morphological differentiation (QST>FST). Shape vector
comparisons further indicate that thermal plasticity (hot-to-cold) does
not mirror patterns of latitudinal divergence (south-to-north), as might
have been expected under a scenario with temperature as the major agent of
selection. Our findings illustrate the importance of detailed
phylogeographic information when interpreting geographic clines of
dispersal traits in an adaptive evolutionary framework.