Many invasive species exhibit rapid evolution of behavioural traits that facilitate dispersal, such as locomotor activity, risk-taking and exploration. In invasive Australian cane toads, variation in morphology and behaviours linked to dispersal coincide with spread across their expanding range; for example, invasion front cane toads are more exploratory than are those from the range-core. However, little is known about the role of genetic mechanisms that may underpin these shifts in behaviour during the cane toad invasion. Because behavioural traits that assist dispersal facilitate range expansion, we predict that genes underlying those traits may be differentially expressed across the cane toad’s invasive range.
We used RNAseq data to analyse gene expression in whole brain tissue from wild-caught toads sampled across a transect from the original introduction site to the invasion front.
We identified 17 differentially expressed genes and cluster analysis revealed that genes associated with assisting spatial memory, central nervous system repair, DNA repair and reduction of oxidative stress were up-regulated towards the invasion front. Conversely, genes associated with learning ability, increased toxin resistance, and dealing with stress are up-regulated at the original introduction site.
This study demonstrates that both physiological and behavioural changes are associated with range expansion and may highlight important candidate genes underpinning invasion ability in this species. This knowledge is vital to future gene technologies, which may assist in the management of both invasive and conserved populations.
Funding provided by the Australian Research Council (DE150101393).