The influence of environmental quality on sexual selection in Nauphoeta cinerea (Dictyoptera: Blaberidae)

Abstract

We examined the impact of environmental conditions on the sex pheromone and mating behavior of the cockroach, Nauphoeta cinerea. Previous research on this species has shown that female behavior during courtship reflects female mate choice, male behavior correlates with male social status, and the male sex pheromone is the character used by females to assess males. In the present study, males and females were allowed to develop from adult emergence to sexual maturity in either a high- or low-quality environment. The environment affected the quantities of sex pheromone components. We found significantly less 3-hydroxy-2-butanone and 4-ethyl-2-methoxyphenol, but not 2-methylthiazolidine, in the pheromone glands of males from a poor environment. Pheromone quality was also affected; the ratios involving 2-methylthiazolidine were altered, while the ratio 3-hydroxy-2-butanone to 4-ethyl-2-methoxyphenol did not change. Development to sexual maturity under these environmental conditions also influenced male and female sexual behavior. Male courtship activity reflected environmental influences; males from the low-quality environment took longer to initiate courtship and spent more time copulating with females from all environments. Male quality, as assessed by females, was also affected by their environment. Females were slower to respond to the courtship of males from the poor environment, regardless of the females' own rearing environments. However, females from the low-quality environment also took longer to respond to the courtship, and required more courtship, regardless of the males' rearing environments. Thus, poor environments also increase female choosiness. However, there was only one significant interaction term, suggesting that the environmental effects are general and that females do not show adaptive plasticity in mate choice. Studies of sexual selection that consider the effects of variable environments on behavior as well as the sexually selected morphology in other systems are likely to provide new insights into this evolutionary process