Most animals reproduce sexually. The relatively small proportion of species that reproduce without sex generally are derived from recent sexual species, i.e., they are evolutionary dead ends. There are a very few apparent exceptions to this rule, in which entire evolutionary groups are composed of asexual species. One such is the nothroid oribatid mites, a group of free-living soil mites that have been around since before the dinosaurs. Detailed investigations will be made into the mechanisms of egg formation to test a hypothesis on how a mother mite could asexually produce offspring that do not accumulate deleterious mutations in their DNA, the ultimate fate of typical asexual species. Genes involved specifically in DNA repair during the production of egg cells will also be sought. If these genes are present and active, they could be responsible for reducing the number of mutations passed on to offspring.
Understanding the evolutionary forces responsible for the origin and maintenance of sexual reproduction remains a major challenge in biology. Large bodies of both theory and observation suggest asexual species cannot survive and diversify over long evolutionary time spans. Any exceptions to this generalization are likely to be very informative about what factor or combination of factors keeps sexual reproduction the nearly ubiquitous feature of life that it is.
