Harsh climate good for sex

New Zealand researchers are responsible for an evolutionary science breakthrough which shows that sexual reproduction in challenging climates produces species that thrive, rather than a general theory which argues that it doesn't.

A recently-published study by Auckland University biologist and lecturer Dr Mat Goddard and PhD graduate Jeremy Gray provided insight into how sexual reproduction has evolved and persisted in the natural world.

"It helps us understand why our genetic make up is the way it is, where we came from and more generally the way the natural world works," Goddard said.

It also applied to climate change, in that the changing environment would not be a burden to sexual reproduction, but rather advantageous.

The theory applied to organisms more than humans, but did show that sexual reproduction was not hindered when humans, or "ancestors to humans" were forced to adapt to changing environments in the past.

"According to classic evolutionary theory, sexual reproduction should actually retard species' ability to adapt to complex environments and in the long run prevent the evolution of new species," Goddard said.

"But in the real world, sex is a highly successful strategy that doesn't prevent new species from evolving, so what we see in nature doesn't tally with the theory.

"Our experimental work provides the first explanation for this and supports an alternate evolutionary theory."

Goddard provided the example of two habitats, one hot and one cold, in one environment.

If an organism from the hot habitat had sex with one from the cold then the offspring would be a hybrid.

The classic evolutionary theory suggests the offspring would poorly adapt to either environment, but Goddard and Gray's research shows that it would actually accumulate genetic changes that would help it to survive.

They were able to come to this conclusion after a lengthy experiment involving yeast.

It is a difficult study to conduct on other organisms as it takes decades, if not hundreds of years, to monitor reproduction through a series of generations.

But by studying microbes, such as yeast, the team was able to follow hundreds of generations in just a couple of years.

They first developed special yeast that could be switched from asexual to sexual forms.

Two groups of yeast grown in different environments were allowed to sexually reproduce, to see whether this slowed the species' simultaneous adaptation to both environments as predicted by the classic theory.

Sexual reproduction, however, proved advantageous, and allowed the yeast to more rapidly adapt to both environments.

"If the classic theory were true, then any breeding between groups of organisms adapting to different environments would dramatically slow their evolution.

"So to explain how new species evolve, classical theorists have had to come up with all sorts of convoluted scenarios, like the emergence of 'magic genes' for mate choice to prevent sexual reproduction between populations," Goddard said.

"Our work is much more consistent with what we see in the real world.

"It supports an alternate theory, in which organisms adapting to different environmental niches can live alongside one another and interbreed occasionally, but this doesn't compromise their evolution or the eventual development of new species, in fact sex enhances this process."

The research was funded by a Marsden grant and a University of Auckland PhD scholarship, and was published online in the journal Ecology Letters.