An interesing article by Liza Gross.
Bdelloids are small microscopic invertebrates found in mosses and various freshwater bodies. Since 100 million years ago, all bdelloids are female and yet they have apparently diverged into nearly 400 species, with evolutionary patterns of divergence similar to sexually reproducing taxa. Main reason for the divergence apparent arose as adaptations to different food sources encountered in different niches.
For the whole article please read:
Gross L (2007) Who Needs Sex (or Males) Anyway? PLoS Biol 5(4): e99 doi:10.1371/journal.pbio.0050099