Male and female genitalic variation in populations of the giant water bug Belostoma angustum Lauck, 1964 (Insecta, Belostomatidae) and mechanisms driving this variation

Abstract

Geographic variation in morphological characters provides an opportunity to understand evolutionary processes. The male genitalia of Belostoma is the main source of characters usually helpful when trying to identify species, but mechanisms that drive variation of genitalic structures have received little attention and remain largely unclear. Hypotheses of sexual selection, species isolation, and pleiotropy predict overall levels of geographic variation that reflect divergent sexual selection pressures or genetic drift. In order to understand the mechanisms that drive genital variation in Belostoma angustum we propose to investigate morphological variation in genitalic and nongenitalic traits of male and female genitalia of individuals from populations of B. angustum of the Pampa's highlands in southern Brazil. This work will be conducted under the supervision of Dr. Göran Arnqvist at the Department of Ecology and Genetics, University of Uppsala, Sweden. The study will assess variation of intromittent components of male genital morphology (dorsal and ventral sclerites of phallotheca) as well as nonintromittent components (the lateral sclerites of the right paramere) using geometric morphometrics. The form of the second and third valves of the female genital chamber will also be investigated, as well as the length and width of the genital chamber. Information from genital structures will be contrasted with data from nongenitalic traits, such as measurements of head, body and legs. Statistical evaluations will allow, for example, assessments of covariation between male and female morphology across populations and will shed light on the processes involved. (AU)