Theory predicts that costly secondary sexual traits will evolve heightened condition dependence, and many studies have reported strong condition dependence of signal and weapon traits in a variety of species. However, although genital structures often play key roles in intersexual interactions and appear to be subject to sexual or sexually antagonistic selection, few studies have examined the condition dependence of genital structures, especially in both sexes simultaneously. We investigated the responses of male and female genital structures to manipulation of larval diet quality (new versus once-used mung beans) in the bruchid seed beetle Callosobruchus maculatus. We quantified effects on mean relative size and static allometry of the male aedeagus, aedeagal spines, flap and paramere and the female reproductive tract and bursal spines. None of the male traits showed a significant effect of diet quality. In females, we found that longer bursal spines (relative to body size) were expressed on low-quality diet. Although the function of bursal spines is poorly understood, we suggest that greater bursal spine length in low-condition females may represent a sexually antagonistic adaptation. Overall, we found no evidence that genital traits in C. maculatus are expressed to a greater extent when nutrients are more abundant. This suggests that, even though some genital traits appear to function as secondary sexual traits, genital traits do not exhibit heightened condition dependence in this species. We discuss possible reasons for this finding.
Raw body size data
This table contains data pertaining to the raw body size (measured in pixels) of male and female seed beetles. "EL" denotes "elytra length", the proxy for body size. "Diet" is the quality of the dietary medium that the individual was reared from; "Order" is the order in which the mother of the individual was exposed (for example, "UN" denotes that the mother was first exposed to a "used" medium and then a "new" medium), and Family refers to the particular mother-father pairing the individual derived from). "Sex" is simply the sex of the individual ("m" for male and "f" or female).
body_size_data.csv
Male genital trait data
This table contains data pertaining to male seed beetles. The data are log-transformed. "EL" denotes elytra length, the proxy for body size used in this investigation. "Diet" is the quality of the dietary medium that the individual was reared from; "Order" is the order in which the mother of the individual was exposed (for example, "UN" denotes that the mother was first exposed to a "used" medium and then a "new" medium), and Family refers to the particular mother-father pairing the individual derived from). The other columns denote genital traits that are described in the paper itself.
male_data.csv
Female genital trait data
This table contains data pertaining to the genital traits of female seed beetles. "EL" denotes "elytra length", the proxy for body size used in this investigation. "Diet" is the quality of the dietary medium that the individual was reared from; "Order" is the order in which the mother of the individual was exposed (for example, "UN" denotes that the mother was first exposed to a "used" medium and then a "new" medium), and Family refers to the particular mother-father pairing the individual derived from). The other columns denote genital trait that are described in the paper itself. They are log-transformed values. "Log of EL" is included as well as raw EL, because of the need to use a generalized linear model for one of the traits, "Number of spines", which is a discrete rather than continuous variable.
female_data.csv
