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.