Dr. Alexandra Schrempf
Research interests: Sexual selection, aging and reproduction in social insects
Study organisms: Ant species of the genus Cardiocondyla
The genus Cardiocondyla
Cardiocondyla is characterized by a male polymorphism with winged disperser males and wingless fighter males (“ergatoid males”), which engage in fatal fighting over access to the virgin queens eclosing in their natal nest. The convergent loss of winged males in a number of clades and the evolution of mutually tolerant wingless males in a monophylum of single-queen species appear to be derived traits (Heinze et al. 2005). Sexuals mate in the lab within the nests, and the life span of queens is comparatively short (< 1 year), so that the total lifetime reproductive success of queens can be determined.
Mating partners in promiscuous animals may have opposing interests about the future reproductive performance of the female. Males gain most through forcing it to invest maximally in short-term reproduction, while females often benefit more from re-mating and saving resources for future clutches. This sexual conflict has led to the evolution of male genital structures and seminal fluids, which harm the females, prevent them from re-mating, and / or decrease their life expectancy, and to respective counter-measures in the females.
As single mating increases the lifespan of Cardiocondyla obscurior ant queens (see above), we study the effect of double mating on female reproductive output and longevity and investigate with the help of genetic markers (microsatellites) whether both males contribute equally to the offspring of the queen. Preliminary results suggest that only sperm of the first male contributes to the female offspring in this polygynous species.
In monogynous Cardiocondyla species with wingless males only, siblings (male and female offspring of the single queen) mate inside the nest, and accordingly, high inbreeding values have been demonstrated (e.g. 83% in C. batesii, Schrempf et al, BES 2005); nevertheless, data suggest that mating between unrelated individuals happen to a certain degree, and in Cardiocondyla elegans, unrelated sexuals have been detected in foreign unrelated nests (Lenoir et al, 2007). We will examine whether this exchange of foreign sexuals can be seen in other monogynous Cardiocondyla species as well and in detail investigate this phenomenon.