Stress and fitness in parthenogens: is dormancy a key feature for bdelloid rotifers?

Background: Bdelloid rotifers are the most common and abundant group of animals that reproduce by ameiotic parthenogenesis, only. They are common in temporally ephemeral habitats, and it is unclear if they dwell in unstable habitats because are excluded from better conditions by stronger competitors, or because they need unstable conditions for their success. We tested the hypothesis that bdelloids 'require' stressful conditions for their persistence by comparing fitness-related traits of stressed ( desiccated, D) and unstressed ( hydrated, H) lines of two species, Adineta ricciae and Macrotrachela quadricornifera.