The correlation between wing interference patterns and body size in Coniceromyia Borgmeier (Diptera: Phoridae) and its implications to the understanding of the former as a sexually selected trait

Abstract

Wing interference patterns (WIPs) are stable structural color reflections of insect transparent wings. The WIP colors are the result of thin-film interference and vary according to wing thickness and other wing characteristics. These patterns have been thought to play a display role during courtship. Recent empirical studies concluded that WIPs affect male drosophilid attractiveness and that WIP evolution is driven by sexual selection. However, these studies did not account for body size variation, a variable that has been demonstrated to be sexually selected and that may be related to wing thickness and WIP color. I consider herein the possibility that body size could be the trait being selected in these studies, and not the WIPs, with the latter being indirectly selected. A first step to consider this alternative hypothesis would be to demonstrate the correlation between WIPs and body size. I analyzed whether such correlation exists through the phylogenetic tree of the genus Coniceromyia (Diptera: Phoridae) by comparing evolutionary models assuming dependent and independent evolution of both traits. I also investigated whether WIPs are correlated to body size within two species of this genus. Strong evidence was found in favor of the correlation between WIPs and body size in the tree analyzed and within one of the two species. If these results are confirmed as a general pattern, the signaling role of WIPs and their direct relation to sexual selection may be questioned by the alternative hypothesis that body size could be the sexually selected trait in recent studies' experiments.