Adaptive radiations represent some of the most remarkable explosions of
diversification across the tree of life. However, the constraints to rapid diver-
sification and how they are sometimes overcome, particularly the relative roles
of genetic architecture and hybridization, remain unclear. Here, we address
these questions in the Alpine whitefish radiation, using a whole-genome
dataset that includes multiple individuals of each of the 22 species belonging
to six ecologically distinct ecomorph classes across several lake-systems. We
reveal that repeated ecological and morphological diversification along a
common environmental axis is associated with both genome-wide allele fre-
quency shifts and a specific, larger effect, locus, associated with the gene edar.
Additionally, we highlight the possible role of introgression between species
from different lake-systems in facilitating the evolution and persistence of
species with unique trait combinations and ecology. These results highlight
the importance of both genome architecture and secondary contact with
hybridization in fuelling adaptive radiation
