Fig. 1

Distribution map of collection locations and major environmental variables across North America for our three focal species. Panel a shows collection records for each of D. novamexicana (green), D. a. americana (blue), and D. a. texana (red) as obtained from the TaxoDros database (taxodros.uzh.ch, see methods). Closed circles indicate the nine sample locations for populations used in this study. Panel b-d show heatmaps of spatial variation in annual mean temperature (b), annual mean radiation (c), and annual mean moisture index (d), as obtained from the Worldclim and Climond databases. Cuticle dissection images inset into Panel A are representative male cuticles from (left to right) Grand Junction, Colorado, White River, Arkansas, and New Orleans, Louisiana