@article{1551,
  abstract     = {Reciprocal coevolution between host and pathogen is widely seen as a major driver of evolution and biological innovation. Yet, to date, the underlying genetic mechanisms and associated trait functions that are unique to rapid coevolutionary change are generally unknown. We here combined experimental evolution of the bacterial biocontrol agent Bacillus thuringiensis and its nematode host Caenorhabditis elegans with large-scale phenotyping, whole genome analysis, and functional genetics to demonstrate the selective benefit of pathogen virulence and the underlying toxin genes during the adaptation process. We show that: (i) high virulence was specifically favoured during pathogen–host coevolution rather than pathogen one-sided adaptation to a nonchanging host or to an environment without host; (ii) the pathogen genotype BT-679 with known nematocidal toxin genes and high virulence specifically swept to fixation in all of the independent replicate populations under coevolution but only some under one-sided adaptation; (iii) high virulence in the BT-679-dominated populations correlated with elevated copy numbers of the plasmid containing the nematocidal toxin genes; (iv) loss of virulence in a toxin-plasmid lacking BT-679 isolate was reconstituted by genetic reintroduction or external addition of the toxins.We conclude that sustained coevolution is distinct from unidirectional selection in shaping the pathogen's genome and life history characteristics. To our knowledge, this study is the first to characterize the pathogen genes involved in coevolutionary adaptation in an animal host–pathogen interaction system.},
  author       = {El Masri, Leila and Branca, Antoine and Sheppard, Anna and Papkou, Andrei and Laehnemann, David and Guenther, Patrick and Prahl, Swantje and Saebelfeld, Manja and Hollensteiner, Jacqueline and Liesegang, Heiko and Brzuszkiewicz, Elzbieta and Daniel, Rolf and Michiels, Nico and Schulte, Rebecca and Kurtz, Joachim and Rosenstiel, Philip and Telschow, Arndt and Bornberg Bauer, Erich and Schulenburg, Hinrich},
  journal      = {PLoS Biology},
  number       = {6},
  pages        = {1 -- 30},
  publisher    = {Public Library of Science},
  title        = {{Host–pathogen coevolution: The selective advantage of Bacillus thuringiensis virulence and its cry toxin genes}},
  doi          = {10.1371/journal.pbio.1002169},
  volume       = {13},
  year         = {2015},
}

@article{1998,
  abstract     = {Immune systems are able to protect the body against secondary infection with the same parasite. In insect colonies, this protection is not restricted to the level of the individual organism, but also occurs at the societal level. Here, we review recent evidence for and insights into the mechanisms underlying individual and social immunisation in insects. We disentangle general immune-protective effects from specific immune memory (priming), and examine immunisation in the context of the lifetime of an individual and that of a colony, and of transgenerational immunisation that benefits offspring. When appropriate, we discuss parallels with disease defence strategies in human societies. We propose that recurrent parasitic threats have shaped the evolution of both the individual immune systems and colony-level social immunity in insects.},
  author       = {El Masri, Leila and Cremer, Sylvia},
  journal      = {Trends in Immunology},
  number       = {10},
  pages        = {471 -- 482},
  publisher    = {Elsevier},
  title        = {{Individual and social immunisation in insects}},
  doi          = {10.1016/j.it.2014.08.005},
  volume       = {35},
  year         = {2014},
}

@article{2846,
  abstract     = {The Red Queen hypothesis proposes that coevolving parasites select for outcrossing in the host. Outcrossing relies on males, which often show lower immune investment due to, for example, sexual selection. Here, we demonstrate that such sex differences in immunity interfere with parasite-mediated selection for outcrossing. Two independent coevolution experiments with Caenorhabditis elegans and its microparasite Bacillus thuringiensis produced decreased yet stable frequencies of outcrossing male hosts. A subsequent systematic analysis verified that male C. elegans suffered from a direct selective disadvantage under parasite pressure (i.e. lower resistance, decreased sexual activity, increased escape behaviour), which can reduce outcrossing and thus male frequencies. At the same time, males offered an indirect selective benefit, because male-mediated outcrossing increased offspring resistance, thus favouring male persistence in the evolving populations. As sex differences in immunity are widespread, such interference of opposing selective constraints is likely of central importance during host adaptation to a coevolving parasite.},
  author       = {El Masri, Leila and Schulte, Rebecca and Timmermeyer, Nadine and Thanisch, Stefanie and Crummenerl, Lena and Jansen, Gunther and Michiels, Nico and Schulenburg, Hinrich},
  journal      = {Ecology Letters},
  number       = {4},
  pages        = {461 -- 468},
  publisher    = {Wiley-Blackwell},
  title        = {{Sex differences in host defence interfere with parasite-mediated selection for outcrossing during host-parasite coevolution}},
  doi          = {10.1111/ele.12068},
  volume       = {16},
  year         = {2013},
}