Journal article

Stabilizing factors interact in promoting host–parasite coexistence

  • Flatt, Thomas Department of Biology, Unit of Ecology and Evolution, University of Fribourg, Switzerland - Department of Ecology and Evolutionary Biology Brown University, Providence, USA
  • Scheuring, István Department of Plant Taxonomy and Ecology, Research Group of Ecology and Theoretical Biology, Eötvös University and Hungarian Academy of Science, Budapest, Hungary
Published in:
  • Journal of Theoretical Biology. - 2004, vol. 228(2), no. 241
English Understanding the mechanisms that promote coexistence among species is a fundamental problem in evolutionary ecology. Such mechanisms include environmental noise, spatial population structure, density dependence, and genetic variation. In natural populations such factors may exert combined effects on coexistence. Thus, to disentangle the contribution of several factors to coexistence, their effects have to be considered simultaneously. Here we investigate the effects of Ricker-type density dependence, genetic variation, and the frequency of sex on host–parasite coexistence, using Nicholson–Bailey models with and without host density dependence. Interestingly, a low frequency of sex (and the genetic variation induced by sex) is the most important factor in explaining the stability of the host–parasite interaction. However, the carrying capacity K and the frequency of sex interact in affecting coexistence. If K is low (strong density regulation), coexistence is easily attained in the density-dependent model, independently of the frequency of sex. In contrast, for high values of K (weak density regulation), low frequencies of sex considerably improve coexistence. Thus, our results suggest that coexistence among species may strongly depend on interactions among several stabilizing factors. These results seem to be robust since they remain qualitatively unchanged if one assumes (1) Beverton–Holt-type or genotype-specific rather than Ricker-type density dependence in the host, or (2) different genotype-specific susceptibilities of hosts to their parasites, or if one adds (3) moderate levels of environmental stochasticity.
Faculté des sciences et de médecine
Département de Biologie
  • English
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