War drums: Drivers of advertisement call variation in an invasive species

Invasive species offer exceptional opportunities to study rapid evolution. They encounter novel environments and selective pressures as they expand their range. The cane toad (Rhinella marina), which was introduced to Australia in 1935 and expanded its range ever since, has undergone significant morphological, behavioral, and ecological changes. Vocal communication, particularly advertisement calls, can evolve quickly under natural and sexual selection, especially in response to environmental and morphological changes. Although Cane Toad calls have been used to lure individuals for control efforts, little is known about geographic variation in their advertisement calls across Australia. Given their extensive spread and documented physiological and morphological changes, variation in call structure may reflect rapid evolution. To explore this, we analyzed Cane Toad calls sourced from FrogID, a citizen science database, and measured spectral and temporal features using Raven Pro. We examined how environmental variables (e.g., temperature, vegetation, and rainfall) and time since colonization influence call variation across Australia. Although analyses are still underway, we predict that we will find geographic differences mainly in peak frequency and call duration, shaped by environmental gradients and invasion history. This could offer insight into how communication traits can rapidly evolve in novel environments.