Male persistence in mating attempts in the face of unwilling females, results because males typically benefit by mating with as many partners as possible. The cost of this persistence to females and how they have responded to it are poorly understood, but can be investigated in damselfly species in which females exhibit multiple color forms. Females can be blue like the males, green, or of intermediate color pattern. Males learn to identify the color variants as potential mates, and often mistake females of other species as mates. Then, species-specific female plates usually prevent the males from forming a mating lock. Color variation is thought to reduce harassment by making it more difficult for mate-searching males to locate females. This will be tested by comparing the search efficiency of males looking for two color types versus a single female type. Egg production under varying male densities will be measured to assess the cost of harassment. A breeding experiment will determine whether the color variation represents genetically distinct female types. Measurement of population density, signal characteristics (using spectroradiometry), and harassment rates in female-variable and female-invariable species in the field will further test whether color variation functions in mate avoidance, and determine if harassment of other species increases with signal similarity of species that occur together. These investigations will increase our understanding of the reproductive cost of harassment by males, the cost of female signal variation to males, and how signal variation is maintained in populations. If, as expected, female color variation is shown to be an adaptation for male avoidance, then this work would suggest how sexual conflict could spur the divergence of populations into new species. Broader impacts of the work include exposing undergraduates to the culture of research and assisting in K-12 workshops on teaching evolution.
