Abstracts (first author)


Evolutionary consequences of female promiscuity

Author(s): Timmermeyer N, Michiels NK, Phillips PC


To cope with stressful conditions like parasite attacks or temperature changes, females can increase their offspring diversity and fitness by mating multiply with several males. This can result in male harm but can be advantageous in fluctuating environments. Populations with promiscuous females therefore are supposed to be more stable than populations with monogamous females. We study the gonochoristic nematode Caenorhabditis remanei, which is mating multiply and affected by male harm. Using experimental evolution, we were able to show that females, in contrast to males, were able to adapt to sex ratio manipulations. Additionally, offspring of promiscuous females had a higher fitness than monogamous females under the influence of the microparasite Bacillus thuringiensis. Even though a powerful tool to investigate fitness effects, manipulating sex ratios in nematodes in scientifically meaningful numbers is very work intensive if done by hand. To increase the population size and replicate number and therefore decrease the effects of drift, we are using differently labeled males and females and an automated sorting device. Worms are loaded onto a polymeric silicon chip (PDMS) and screened for fluorescent makers, resulting in separated males and females, which can be combined in different sex ratios depending on the treatment. These populations will be tested under stressful conditions to investigate whether populations with promiscuous females are more resistant to stressful changes in their environment compared to the monogamous control. Additionally, individual females will be compared to analyze within and between population fitness.

Abstracts (coauthor)

A stumbling Red Queen: host-parasite coevolution handicapped by Feeble males

Author(s): Masri, L, Schulte RD, Timmermeyer N, Thanisch S, Crummenerl L, Jansen G, Michiels NK, Schulenburg H


Our work highlights the potential influence of intra-specific variations among the sexes in immunocompetence on host-parasite coevolution. In particular, the Red Queen hypothesis proposes that coevolving parasites select for outcrossing in the host. Outcrossing relies on males, which often show lower immune investment as a consequence of sexual selection. Here, we show that such sex-specific variation in immunity significantly interferes with parasite-mediated selection. Two independent coevolution experiments with Caenorhabditis elegans and its microparasite Bacillus thuringiensis produced a decreased yet stable frequency of outcrossing male hosts. Subsequent tests verified that male C. elegans suffered from a direct selective disadvantage. In the presence of its microparasite, males showed lower survival, decreased sexual activity, and altered escape behavior. Each of these responses can reduce outcrossing frequencies. At the same time, males also offered an indirect selective benefit, because male-mediated outcrossing increased offspring resistance. As such intra-specific variations in immunity are widespread among animals, the resulting interference of opposing selective constraints may impose a fundamental limit to host adaptation during antagonistic coevolution.


Chairman: Octávio S. Paulo
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XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon


Computational Biology & Population Genomics Group