“…Without knowledge of the exact genomic basis and heritability of these traits, it is difficult to precisely determine which forces have shaped phenotypic variation (Mitchell_Olds et_al.,_2007). However, when combined with genome_wide genetic data, phenotypic information can provide insight into which mechanisms might have played a role in driving the origins of phenotypic variation (Cabanne, Trujillo_Arias, Calder_n, D_Horta, & Miyaki,_2014; Rausher & Delph,_2015). For example, if geographical patterns of phenotypic variation coincide closely with historical barriers to dispersal (IBH) or change clinally with geographical distance (IBD), phenotypic differences among populations might have evolved primarily as a byproduct of genetic drift, potentially reinforced by natural selection across the barrier or along the cline (Lande,_1980).…”