Unravelling the interplay among genes, networks, and signalling molecules is key to understanding how many natural populations adapt. Although the impact of gene expression on trait regulation and evolution has been recognised for many decades, its role in the evolution of adaptations is still a subject of intense exploration. Using a hybrid population derived from two contrasting ecotypes of an Australian wildflower, Senecio lautus, we investigated the role of gene expression divergence in their origins. Coastal ecotypes of S. lautus have contrasting vegetative heights and gravitropic behaviours that evolved independently many times, highlighting the role of natural selection in their evolution. We examined gene expression in 10 gravitropic and 10 agravitropic hybrid families from the hybrid population of Senecio at Lennox Head, NSW. We found 428 genes that showed differential expression between the gravitropic control and treatment groups when we rotated the hybrids 90 degrees. Of these, 81 genes (~19%) had predicted functions linked to several plant hormones. Using knowledge from Arabidopsis mutant screens and assessing our gene networks, we construct a model for differences in gravitropism between ecotypes that relies on modulating the movement and accessibility of the hormone auxin, known to control the gravitropic response across plants. Our findings suggest a role for the hormonal control of gravitropism in plant adaptation to coastal environments, where ecotypes are known to differ from their counterparts in other habitats. More generally, we posit that the genetics of adaptation encompasses the evolution of intertwined signalling pathways that ultimately contribute to the origin of new ecotypes.