Résumé
Ecological speciation requires divergent selection, reproductive
isolation, and a genetic mechanism to link the two. We examined the role
of gene expression and coding sequence evolution in this process using two
species of Howea palms that have diverged sympatrically on Lord Howe
Island, Australia. These palms are associated with distinct soil types and
have displaced flowering times, representing an ideal candidate for
ecological speciation. We generated large amounts of RNA-Seq data from
multiple individuals and tissue types collected on the island from each of
the two species. We found that differentially expressed loci as well as
those with divergent coding sequences between Howea species were
associated with known ecological and phenotypic differences, including
response to salinity, drought, pH and flowering time. From these loci we
identified potential ‘ecological speciation genes’, and further validate
their effect on flowering time by knocking out orthologous loci in a model
plant species. Finally, we put forward six plausible ecological speciation
loci, providing support for the hypothesis that pleiotropy could help to
overcome the antagonism between selection and recombination during
speciation with gene flow.