Frequency‐dependent resemblance of male‐colored females to males in a damselfly

Dear editor, Mimetic protection is most effective when mimics are relatively rare (Pfennig et al., 2001). In polymorphic damselfly species, male-colored female morphs may avoid costly male mating attempts because they are not immediately recognized as a suitable mating partner (van Gossum et al., 2008). We investigated morphological resemblance of male-colored females to males across six populations of the polymorphic blue-tailed damselfly Ischnura elegans (Vander Linden). We found that male-colored females resembled males more closely with an increasing ratio of male-colored females to other female morphs. Our results suggest that the degree of mimetic fidelity is frequencydependent. Genetically determined color polymorphisms have evolved throughout the tree of life and studying them helps in understanding the selective forces that affect the maintenance of genetic diversity (Gray & McKinnon, 2007). In some species, color polymorphism is limited to one sex. Such sex-limited color polymorphisms has probably evolved in response to sex-specific predation, sexual competition, or sexual conflict (Stamps & Gon III, 1983; Gross, 1996; Svensson et al., 2009). In I. elegans, mature males occur in one color (blue) and mature females occur in three genetically controlled color morphs (Sánchez-Guillén et al., 2005): infuscans (olive green), rufescens-obsoleta (brown-red) and androchrome (“male-colored”: blue or green-blue). In this species, females suffer from excessive male mating harassment, which is costly in terms of female fitness (Gosden & Svensson, 2009). Female morph frequencies differ greatly between populations (Cordero-Rivera & Sánchez-Guillén, 2007) and frequency-dependent male