Biodiversity encourages disease resistance

"The result was rather astounding," said researcher Corey Bradshaw.

By Brooks Hays

ADELAIDE, Australia, March 22 (UPI) -- Ecologists like to tout the less obvious benefits of biodiversity, and rightfully so. Now, they've got another to boast about -- disease resistance.

"There are two main theories about the biodiversity-disease relationship in non-human species," Corey Bradshaw, a professor of climate science at the University of Adelaide's Environment Institute, said in a news release.


"One is that with more species there is a greater pool of potential hosts for pathogens, so pathogens increase as biodiversity increases," he continued. "The other asserts that disease decreases with higher diversity because of a 'dilution' effect, where the chance of a pathogen meeting its host species is reduced."

To identify which of the two theories best described reality, Bradshaw and his colleagues began conducting experiments in plots of a Tibetan alpine meadow.

According to Bradshaw, previous attempts have confused biodiversity and abundance. His research team ensured their experimental plots possessed equal species richness and abundance by removing specific groups of species.

"Our experiments ... used natural communities and species with similar abundance so we could control for confounding effects of species richness and abundance," Bradshaw explained.

Their experiment results mimicked the "dilution" effect almost exactly. Fungal disease was much less prevalent in plots with higher biodiversity.


"The result was rather astounding," said Bradshaw. "We showed unequivocally that greater biodiversity among the meadow plants reduced the overall incidence of fungal disease, even though there were more pathogens."

The research was published in the journal Ecology.

In a second experiment, the researchers showed that warming and fertilization diminished the benefits of biodiversity.

"Most interestingly, we showed that artificial fertiliser weakened the dilution effect of increasing host biodiversity, most likely by enhancing fungal spore production, infection success and lesion growth by the hosts," explained co-author Shurong Zhou, a professor at Fudan University's School of Life Sciences. "Changing the delicate balance of a healthy community not only resulted in more pathogens but weakened the overall community's resistance to disease."

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