Effects of the maternal social environment on the mating signals and mate preferences of adult offspring in Enchenopa treehoppers

Much is known about how the maternal environment can shape offspring traits via intergenerational effects. It is less clear, however, whether such effects may reach adult offspring sexual traits, with potential consequences for sexual selection and speciation. Here, we report effects of adult female aggregation density on the mating signals and mate preferences of their offspring in an insect that communicates via plant-borne vibrational signals. We experimentally manipulated the density of aggregations experienced by egg-laying mothers, reared the offspring in standard densities, and tested for corresponding differences in their signals and preferences. We detected a strong effect in male signals, with sons of mothers that experienced low aggregation density signaling more. We also detected a weak effect on female mate preferences, with daughters of mothers that experienced low aggregation density being less selective. These adjustments may help males and females find mates and secure matings in low densities, if the conditions they encounter correspond to those their mothers experienced. Our results thus extend theory regarding adjustments to the social environment to the scale of intergenerational effects, with maternal social environments influencing the expression of the sexual traits of adult offspring.

Methods
Creating treatments and rearing
We assigned mated females to three different density treatments (high, medium, and low) during egg-laying and then reared their offspring in a standard density. Once adults, we assayed these offspring to determine if maternal aggregation density during egg-laying influenced mate preference and/or courtship displays.

Female data
We generated female preference data by playing each individual female a randomized sequence of artificial male signals and recording the number of female responses to these signals. The signals were only different in their dominant frequency and each signal was played three times in a row (so that females could respond 0–3 times per frequency).

We then generated a spline of each female preference using the program PFunc so that we could generate a preference function with which we could compare the shape of the functions across treatments.

Male data
Males signal spontaneously, thus we placed males on a recording plant and recorded their signals. We measured aspects of the male signal using the program audacity.