First brain de-novo transcriptome of Tyrrenhian tree frog, Hyla sarda, for the study of dispersal-related behavioral variation

Dispersal is a key process in ecology and evolution as it contributes to shaping the spatial patterns of biological diversity at all its levels of organization. Growing evidence is unveiling the role of phenotypic trait variation in affecting dispersal dynamics of populations, and that substantial, rapid, and directional changes in the phenotypic makeup of populations would occur during range expansions by spatial sorting of dispersal-related traits. Accordingly, selective pressures at the front of a range expansion wave would actively promote individuals with higher dispersal abilities. Although many studies have been focusing on phenotypic trait evolution during range expansion, its genomic underpinnings are almost unexplored, hampering a thorough understanding of the evolutionary processes involved during dispersal. The Tyrrhenian tree frog Hyla sarda is a small amphibian endemic to the Tyrrhenian islands. According to previous phylogeographic studies, H. sarda underwent a northward range expansion from the north of Sardinia (western Mediterranean sea) during the last glacial phase. The colonization of the Corsica island was allowed by the temporary formation of a wide land bridge connecting Sardinia and Corsica, induced by the marine regression occurred during the last glacial maximum. The postglacial loss of this land bridge prevented any subsequent gene flow between Corsican and Sardinian populations. As a consequence, the genetic and phenotypic legacies of this range expansion event can still be detected in current populations, which makes H. sarda an interesting candidate species for the study of the genetic underpinnings of phenotypic trait evolution during range expansions. Here, we contribute to the investigation of the genetic underpinning phenotypic trait evolution during range expansion, by generating the first brain de-novo transcriptome of H. sarda. We focused on the brain transcriptome as behavioural variation at personality traits has been identified as a key component of the dispersal syndromes, substantial personality traits variation has been observed within H. sarda populations, and brain gene expression patterns have been linked to a vast number of behavioural responses to environmental stimuli.