Desiccation-tolerance in bdelloid rotifers facilitates spatiotemporal escape from multiple species of parasitic fungi

Abstract

Asexuality has major theoretical advantages over sexual reproduction. Nevertheless, obligately asexual metazoan lineages seldom endure over evolutionary time. The Red Queen hypothesis posits that their limited capacity to generate genetic novelty leads to extermination by rapidly evolving parasites and pathogens. At first glance, rotifers of the class Bdelloidea appear to contradict this view: they have reproduced asexually for over 30 Myr without being overwhelmed by parasites. However, there are special ecological conditions under which Red Queen models can accommodate this unusual outcome. If hosts disperse rapidly within a structured metapopulation during a parasite-free life stage, then in principle they can become spatiotemporally decoupled from coevolving antagonists, and persist without sex. Intriguingly, bdelloid rotifers form dormant propagules when desiccated, which disperse easily by wind. In previous experiments, 7 days of desiccation and wind dispersal removed a fungal parasite from populations of one bdelloid species, allowing them to disperse independently. Here, I extend this finding to two additional bdelloid species and five more fungal parasites, and demonstrate its robustness under various desiccation regimes, and in the presence of multiple parasites. Results support the hypothesis that the unusual physiology of anciently asexual bdelloid rotifers helps them escape fungal parasites in space and time. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 564–574.