Why is s*x so popular among plants and animals, and why isn’t asexual reproduction, or cloning, a more common reproductive strategy?
Researchers recently tested a theory developed in the 1970s by John Maynard Smith suggesting that s*x is a more costly reproductive strategy than asexual reproduction. Mathematically, he showed that asexual females make more grandchildren than s*xual females. For s*xual females, approximately half their offspring must be sons, and those sons can’t physically bear grandchildren. Asexual females don’t make sons, so they make twice as many daughters as s*xual females. Maynard Smith called this cost of s*x the “two-fold cost of males.” Therefore, asexual lineages should increase in frequency every generation and outcompete s*xual lineages, driving them extinct.
In this latest research, investigators studied the snail Potamopyrgus antipodarum, which has two kinds of females: one is asexual and the other is s*xual and produces both sons and daughters. Asexual females coexist with s*xual females in lakes and streams in New Zealand. When they collected snails from a lake where asexual and s*xual females coexist and allowed them to reproduce in big outdoor tanks, they found that asexual females increased in frequency from parents to offspring, and this increase was consistent with a two-fold cost of s*x.
“Our findings mean that Maynard Smith’s theory does apply to this complex natural system, and s*xual females do pay at least a two-fold cost of s*x,” said Dr. Amanda Gibson, lead author of the Evolution Letters study. “This study provides the first direct estimate of the cost of s*x, and the results validate Maynard Smith’s foundational theory in evolutionary biology. Our experimental confirmation of the two-fold cost of s*x also justifies a continued hunt for the selective forces that favor s*x, because s*x is indeed costly in P. antipodarum.”
via: INFORMATION NIGERIA