|Macrostomum lignano. Picture courtesy of Lukas Schärer.|
Thesis abstract: The relationship between the male and the female function in the simultaneous hermaphroditic flatworm Macrostomum lignano has been intensively studied on a phenotypic level. The results from these studies largely coincide with predictions that derive from sex allocation theory, which assumes a trade-off between the allocation of resources to the sex functions. Results from a recent experimental evolution study suggest that sexually antagonistic genetic variation could also have an impact on the correlation between male and female fitness. Sexually antagonistic genetic variation manifests itself in a negative genetic correlation between male and female fitness and has so far mainly been described in separate-sexed organisms. This study investigates the phenotypic and genetic correlation between the male and female fitness components in M. lignano in two stressful environments; salt stress and food stress. The results suggest that there is no genetic or phenotypic correlation between male and female fitness, despite considerable genetic variation in fitness for both sex functions. However, the residual variation shows a tendency for a negative correlation in a food-restricted environment, which could be an indication of a resource trade-off that is obscured on a phenotypic level by the genetic variation in fitness. It was further found that the genetic variances of both fitness functions are environment dependent.