Detection of environmental and morphological adaptation despite high landscape genetic connectivity in a pest grasshopper (Phaulacridium vittatum)

Widespread species that exhibit both high gene flow and the capacity to occupy heterogeneous environments make excellent models for examining local selection processes along environmental gradients. Here we evaluate the influence of temperature and landscape variables on genetic connectivity and signatures of local adaptation in Phaulacridium vittatum, a widespread agricultural pest grasshopper, endemic to Australia. With sampling across a 900 km latitudinal gradient, we genotyped 185 P. vittatum from 19 sites at 11,408 single nucleotide polymorphisms (SNPs) using ddRAD sequencing. Despite high gene flow across sites (pairwise Fst = 0.0003-0.08), landscape genetic resistance modelling identified a positive non-linear effect of mean annual temperature on genetic connectivity. Urban areas and water bodies had a greater influence on genetic distance among sites than pasture, agricultural areas, and forest. Together, Fst outlier tests and Environmental Association Analysis (EAA) detected 24...