A macroevolutionary perspective of cryptic coloration in sexually dichromatic grasshoppers of the genus Sphenarium (Orthoptera: Pyrgomorphidae).

Abstract

Background matching and disruptive coloration are defense mechanisms of animals against visual predators. Disruptive coloration tends to evolve in microhabitats that are visually heterogeneous, while background matching is favored in microhabitats that are chromatically homogeneous. Controlling for the phylogeny, we explored the evolution of the coloration and the marking patterns in the sexual dichromatic and widely distributed neotropical grasshoppers of the genus Sphenarium. These grasshoppers represent an excellent model to investigate the evolution of cryptic coloration on insects due to the heterogeneity of the environments where they have evolved. We found a correlation between the grasshoppers' coloration and disruptive markings with the chromatic properties of their environments that was inferred by the levels of precipitation during the rainy season. The results suggest that colors and marking patterns could evolve due to predation pressures. Color in both sexes could offer camouflage that is not perfectly background matched to a single habitat but instead offers a degree of resemblance to multiple backgrounds. Moreover, we found that males and females chromatic properties differ between them and precipitation levels where the species are found. This suggests that the sexes have diverged in their response to the environments, favoring the evolution of sexual dichromatism in these grasshoppers.