Experimental test of the consequences of host-parasite co-evolution

Zusammenfassung der Projektergebnisse

Coevolutionary interactions between host and parasite are predicted to be of prime importance in the evolution of organisms and biological mechanisms. This project focused on a comprehensive experimental test of the consequences of host-parasite coevolution. It is based on evolution experiments under controlled laboratory conditions followed by extensive phenotypic analysis. The approach relies on a unique model system, consisting of the nematode Caenorhabditis elegans as a host and its microparasite Bacillus thuringiensis, which are both ideally suited to a versatile experimental analysis. The results obtained in the different parts of this project demonstrate that coevolution causes multiple phenotypic as well as genetic changes in both antagonists and that coevolutionary selection dynamics differ from those present during one-sided adaptation to a non-evolving antagonist. In detail, coevolution was found to cause (i) reciprocal changes in virulence and resistance, (ii) additional changes in other fitness-related traits in the absence of the antagonist, consistent with a cost of adaptation, (iii) rapid genetic changes in both antagonists, and (iv) increases in genetic diversity within and especially between replicate populations in both antagonists. Moreover, high parasite virulence (i.e. high killing rate) was particularly favoured in response to coevolution and to a lesser extent during one-sided adaptation, whereas it was rapidly lost when the bacteria evolved in the absence of the host. In contrast, high infection rate (i.e. possibly due to high replication rate inside the host) appears to be advantageous during onesided adaptation but to a lesser extent during coevolution, which may indicate a trade-off between different parasite traits relevant for host infection. Furthermore, C. elegans males appear to be important for invasion and spread of novel alleles, which may be advantageous during coevolution with parasites. Taken together, the results of this project emphasize the complexity and high dynamics of evolutionary change associated with host-parasite coevolution.

Projektbezogene Publikationen (Auswahl)

• (2008) Experimental insight into the proximate causes of male persistance variation among two strains of the androdioecious Caenorhabditis elegans (Nematoda). BMC Ecol. 8:12
  Wegewitz V, Schulenburg H, Streit A
  
• (2009) Do males facilitate the spread of novel phenotypes within populations of the androdioecious nematode Caenorhabditis elegans? J. Nematol. 41:247-254
  Wegewitz V, Schulenburg H, Streit A
  
• (2009) Ecological immunology. Phil Trans. R. Soc. B 364: 3-14
  Schulenburg H, Kurtz J, Moret Y, Siva-Jothy M
  
• (2010) Multiple reciprocal adaptations and rapid genetic change upon experimental coevolution of an animal host and its microbial parasite. Proc. Natl. Acad. Sci. USA 107:7359–7364
  Schulte RD, Makus C, Hasert B, Michiels NK, Schulenburg H
  
• Host-parasite local adaptation after experimental evolution of Caenorhabditis elegans and its microparasite Bacillus thuringiensis. Proc. R. Soc. Lond. B.
  Schulte R, Makus C, Hasert B, Michiels NK, Schulenburg H