The importance of being a bdelloid: Ecological and evolutionary consequences of dormancy

The bdelloid rotifers represent an intriguing example of organisms displaying an array of unusual ecological and evolutionary features, yet have managed to remain an extremely successful group for more than 35 million years. Some of these unusual features include: strictly parthenogenetic reproduction, degenerate tetraploidy, horizontal gene transfer, and resistance to desiccation, starvation and ionising radiation. This review emphasises these as well as other ecological and evolutionary features of bdelloids, highlighting the current knowledge regarding the patterns and processes governing these organisms. We suggest a unifying framework, with dormancy representing the bdelloids' key feature. We hypothesise that dormancy, and especially the DNA repair mechanisms activated during dormancy recovery, might be responsible for all the unusual features present in the taxon. We propose further work that needs to be performed to test this hypothesis, and recommend further research areas that will help to unravel this "evolutionary scandal''.