Desiccation-tolerance in bdelloid rotifers facilitatesspatiotemporal escape from multiple species ofparasitic fungi

摘要

Asexuality has major theoretical advantages over sexual reproduction. Nevertheless, obligately asexual metazoanlineages seldom endure over evolutionary time. The Red Queen hypothesis posits that their limited capacity togenerate 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 Myrwithout being overwhelmed by parasites. However, there are special ecological conditions under which Red Queenmodels can accommodate this unusual outcome. If hosts disperse rapidly within a structured metapopulationduring a parasite-free life stage, then in principle they can become spatiotemporally decoupled from coevolvingantagonists, 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 fungalparasite from populations of one bdelloid species, allowing them to disperse independently. Here, I extend thisfinding to two additional bdelloid species and five more fungal parasites, and demonstrate its robustness undervarious desiccation regimes, and in the presence of multiple parasites. Results support the hypothesis that theunusual physiology of anciently asexual bdelloid rotifers helps them escape fungal parasites in space and time.