Data from: Genetic variation for adaptive traits is associated with polymorphic inversions in Littorina saxatilis

Chromosomal inversion polymorphisms, segments of chromosomes that are
flipped in orientation and occur in reversed order in some individuals,
have long been recognized to play an important role in local adaptation.
They can reduce recombination in heterozygous individuals and thus help to
maintain sets of locally adapted alleles. In a wide range of organisms,
populations adapted to different habitats differ in frequency of inversion
arrangements. However, getting a full understanding of the importance of
inversions for adaptation requires confirmation of their influence on
traits under divergent selection. Here, we studied a marine snail,
Littorina saxatilis, that has evolved ecotypes adapted to wave exposure or
crab predation. These two types occur in close proximity on different
parts of the shore. Gene flow between them exists in contact zones.
However, they exhibit strong phenotypic divergence in several traits under
habitat-specific selection, including size, shape and behaviour. We used
crosses between these ecotypes to identify genomic regions that explain
variation in these traits by using QTL analysis and variance partitioning
across linkage groups. We could show that previously detected inversion
regions contribute to adaptive divergence. Some inversions influenced
multiple traits suggesting that they contain sets of locally adaptive
alleles. Our study also identified regions without known inversions that
are important for phenotypic divergence. Thus, we provide a more complete
overview of the importance of inversions in relation to the remaining
genome.