Friday, February 17, 2006

Even educated water-fleas do it...

In the current issue of Science, Paland & Lynch report on some new evidence in favor one of the "Weismann-family" theories for the evolution of sex I mentioned the other day. They compared sexual and asexual populations of water-fleas (Daphnia pulex) and found that sexual populations are more efficient at eliminating deleterious mutations than asexuals, as predicted by (among others) the mutational deterministic hypothesis:

"Of the amino acid altering mutations arising in mitochondrial protein-coding genes of D. pulex, we estimate that 73.2% have strongly deleterious effects and are subject to purifying selection irrespective of the population's breeding system, 13.3% have moderately deleterious effects and persist only in asexual populations, 4.4% are mildly deleterious and allowed to persist in the short-term even in sexual populations, and 9.1% are effectively neutral. Thus, the rate of accumulation of deleterious amino acid–altering mutations in asexual lineages, 4.4+13.3=17.7%, is four times as high as that for sexual lineages (4.4%)."