Trade-offs in female signal apparency to males offer alternative anti-harassment strategies for color polymorphic females

Color polymorphisms are known to influence receiver behavior, but how they affect a receiver's ability to detect and recognize individuals in nature is usually unknown. I hypothesized that polymorphic female damselflies represent an evolutionary stable strategy, maintained by trade-offs between the relative apparency of morphs to male receivers. Using field experiments on Enallagma hageni and focal studies of E. hageni and E. boreale, I tested for the first time the predictions that 1) green heteromorphs and blue andromorphs gain differential protection from sexual harassment via background crypsis and sexual mimicry respectively, and 2) female morphs behaviorally optimize their signal apparency to mate-searching males. First, based on male reactions elicited by females, against a high contrast background the two morphs did not differ in being detected by males and once detected, did not differ in being recognized (eliciting sexual reactions). However, on green ferns, heteromorphs were ...