“No Sex for 40 Million Years? No Problem.”
Science Daily
March 20, 2007
Micorscopic animals known as Bdelloid Rotifers have never had sex in all of its 40 million years of existence. Species like this that reprodce asexually have never lived as long as the Bdelloid Rotifers. Scientists have always thought that in order to evolve into a distince species, sexual reproduction was necessary. But this recent discovery has challenged that assumption and has provided scientists with a new perspective on why species evolve in the first place.
These microscopic creatures live mostly in wet habitats such as ponds, rivers, streams, and mosses. The Bdelloid Rotifers reproduce asexually by producing eggs that are genetic clones of their mother. Therefore this species has no males whatsoever. Fossil records show that the Bdelloid Rotifers have been around for over 40 million years without sexually repoducing, yet have evolved into a diverse and distinct species.
To test this, scientists used DNA sequencing and took measurements of the jaws. They took specimens from parts of the UK, Italy, and other parts of the world and found that they had all adapted to survive in their environments as a distinct species. Dr. Tim Barraclough from Imperial College London’s Division of Biology had explained that natural selection has caused the divergence in distinct creatures that act as though they were produced sexually.
Scientists had previously thought that random mutations during the cloning process had allowed the species to survive in different habitats. But the recent study shows that a theorized process call divergent selection has caused these mutations, and not a random selection.