Inhibition of HSP90 causes morphological variation in the invasive ant Cardiocondyla obscurior.

Canalization underlies the expression of steady phenotypes in the face of unsteady environmental conditions or varying genetic backgrounds. The chaperone HSP90 has been identified as a key component of the molecular machinery regulating canalization and a growing body of research suggests that HSP90 could act as a general capacitator in evolution. However, empirical data about HSP90-dependent phenotypic variation and its evolutionary impact is still scarce, particularly for non-model species. Here we report how pharmacological suppression of HSP90 increases morphological variation up to 87% in the invasive ant Cardiocondyla obscurior. We show that workers treated with the HSP90 inhibitor 17-DMAG are significantly more diverse compared to untreated workers in two of four measured traits: maximal eye distance and maximal propodeal spine distance. We further find morphological differentiation between natural populations of C. obscurior in the same traits that responded to our pharmacological treatment. These findings add support for the putative impact of HSP90 on canalization, the modularity of phenotypic traits, and its potential role in morphological evolution of ants.