Proximate mechanisms underlying the rapid modification of phenotypic traits in cane toads (Rhinella marina) across their invasive range within Australia

Biological invasions often involve rapid modification of phenotypic traits, presumably in response to the host of novel pressures to which an invader is exposed, but the proximate basis for those changes remains unclear. Phenotypic changes may be generated by environmental factors (E), genetic factors (G), or the interaction between these two processes (GE). To explore this issue, we obtained eight clutches of the cane toad (Rhinella marina) from three regions across its invaded range within Australia, and raised the offspring under standard conditions (diet and/or exercise level manipulations) to clarify the proximate underpinnings of geographic divergence in phenotypic traits. Our results demonstrate that phenotypic variation among Australia cane toad populations are affected by genetics and environment, and an interaction of these two processes. Some traits (e.g., sprint distance) differed among populations, suggesting a heritable basis. Other traits (e.g., relative heart mass) were ...