Does the addition of a new signalling trait enhance receiver responses in diurnal geckos?

Animal signals in multiple modalities expands the opportunity for effective communication. Among diurnal geckos of the genus Cnemaspis, chemical signalling traits preceded the evolution of visual traits. Males of all species possess chemical secreting ventral glands, but only in some species, males also express yellow gular patches. This difference in the expression of unimodal or multimodal signalling traits between closely related species provided us with an opportunity to understand the use of multimodal signals for communication. We studied receiver responses in Cnemaspis indica, a sexually monochromatic species, and in C. littoralis, a species where males possess yellow gulars. We performed behavioural trials where individuals of each species were exposed to only chemical stimuli, only visual stimuli, or both chemical and visual stimuli simultaneously from male and female conspecifics. Our results show that only chemical stimuli were necessary and sufficient to elicit responses in males and females of C. indica as well as in females of C. littoralis. However, males of the dimorphic C. littoralis required the multimodal stimulus to elicit movement-based responses. Our results suggest that the evolution of colour traits in diurnal geckos is associated with a partial shift in some receiver responses toward multimodal communication, with no addition to the behavioural repertoire.

Automated summary

The study found that the evolution of color traits in diurnal geckos is associated with a shift in receiver responses towards multimodal communication, without adding to the behavioral repertoire. Chemical signals play a crucial role in eliciting responses in both male and female individuals of certain species. However, males of dimorphic species require a combination of chemical and visual stimuli for movement-based responses.