Studies by scientists at the University of California, Santa Barbara show that sexual reproduction wins out, in an evolutionary sense, over asexual reproduction in a major study that included 34 experiments with the common fruit fly Drosophila melanogaster.
Specifically, they discovered that the rate of progressive evolution (the accumulation of beneficial mutations) is faster in populations that reproduce sexually.
"However, there is a high cost associated with producing males," said William R. Rice, first author and professor of biology at the UC, Santa Barbara. "Just do the math and you will see. And yet, look out the window and almost every organism you see reproduces sexually."
The math is simple: with four asexual adults (females) you get eight offspring, but with two males and two females you get only four offspring. In other words, the asexual population grows twice as fast as the sexually reproducing one.
The second part of the mathematical advantage is that the asexual adult female is able to put all of her genes into the next generation, whereas with sexual reproduction, each individual is responsible for only half of the genetic information in the offspring.
"Its a dosage cost," said Rice. "My son only has half of my genes; the other half are from his mother. Only half of my genome is getting into the population. However, if I
were an asexual female, my offspring would carry all of my genome. I would put twice as many genes into the next generation. With asexual reproduction you get two times as many offspring and two times as many genes into the popula
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Contact: Gail Brown
gail.brown@ia.ucsb.edu
805-893-7220
University of California - Santa Barbara
18-Oct-2001