4.2 Forward-genetics in the wild
“Top-down” forward-genetic approaches start with a particular trait and dissect its genetic basis. There are few examples of this approach using WGR data in invasion biology. Forward genetic approaches have historically involved QTL mapping in invasive species reared under controlled conditions. However, if an invasiveness trait is easy to score in wild individuals, genome-wide association studies can be used with WGR. For example, the genetic basis of wing length was investigated with admixture mapping using WGR from field-collected samples of introduced honey bees (Apis mellifera ), though no major effect loci were identified (Calfee, Agra, Palacio, Ramírez, & Coop, 2020). In another WGR study, on Aedes aegypti throughout the native sub-Saharan range, a handful of major effect loci underlying preference for human odour were identified (Rose et al., 2020). Although the latter study was conducted within the native range of A. aegypti , the trait of human preference appears to contribute to its spread into urban habitats.