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Abstract:
Chromosomal inversions are frequently documented for their involvement in adaptation and speciation across various organisms. In Littorina fabalis snails on one Swedish island, an inversion on linkage group (LG) 3 is closely associated with wave exposure and size differences: one arrangement is linked with a wave exposed environment and larger snails, while the alternative arrangement is linked with a sheltered environment and dwarf snails. Several other inversions present in these snails have also been shown to be coupled with one another and with the wave exposure gradient, defining two ecotypes that apparently diverged in allopatry . In addition, there is a region on LG 15 that is putatively associated with sex. If chromosomal inversions facilitate rapid adaptation to similar environmental gradients in this system, we hypothesise that the inversion polymorphisms in Swedish L. fabalis will be similarly associated with wave exposure gradients in other areas of the species' range on the coasts of western Europe. Using haplotagging, a scalable linked-read method for large populations, and Illumina sequencing, we test whether the same inversion arrangements are present in populations in UK and Iberia, whether they are also associated with wave exposure and phenotype differences and whether coupling among inversions is maintained. With long-range information from the linked-read haplotags, we test if the inversion arrangements share the same breakpoints and origin between populations. Lastly, we test whether the sex-associated region in Sweden is also consistent among the populations.
