Abstracts (first author)

Talk 

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

Summary:

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.



Abstracts (coauthor)

Rapid genomic changes in pathogenic Bacillus thuringiensis during adaptation to its nematode host

Author(s): Branca, A, Masri L, Sheppard A, Rosenstiel P, Bornberg-Bauer E, Schulenburg H

Summary:

Bacillus thuringiensis is a pathogenic bacterium of invertebrates with a wide host spectrum, including the nematode Caenorhabditis elegans. We studied its ability to adapt to the nematode host with the help of an evolution experiment, during which a mixture of B. thuringiensis strains was either coevolved with C. elegans (coevolution treatment), adapted to a non-changing host population (one-sided adaptation), or evolved in the absence of the host (control evolution). Experimental evolution produced distinct phenotypic changes in virulence and also other life-history traits. Here, I present results on our analysis of the genetic basis of evolutionary changes based on whole-genome sequencing of replicate populations. Firstly, we were able to identify a central role for clonal selection during experimental evolution, especially under coevolution and control conditions. Each of these conditions was dominated by two different chromosomal genotypes, whereas an unexpected variability among replicate populations was observed in the one-sided adaptation treatment. Secondly, we were able to demonstrate that adaptation to the host is additionally influenced by the spread of genomic SNP and indel alleles as well as changes in plasmid composition and presence of phage infection. Taken together, our results highlight that the trajectory of evolution depends on multiple interaction levels: (i) host – pathogen; (ii) competition between pathogen strains and (iii) selfish mobile elements comprised of plasmids and phages.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

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
Portugal

Website

Computational Biology & Population Genomics Group 
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