Biodiversity prevents disease

It has long been presumed that greater biodiversity leads to an increased resistance to infectious disease, but quantifying this theory in a natural rather than planted environment has been tricky.

A recent joint effort between Shanghai’s Fudan University and the University of Adelaide’s Environment Institute has shown a clear link between biodiversity and the severity of a fungal disease on a Tibetan alpine meadow.

The research was headed by Professor Corey Bradshaw, who holds the Sir Hubert Wilkins Chair of Climate Change, in collaboration with Professor Shurong Zhou from the School of Life Sciences at Fudan University.

The study was conducted at the Alpine Meadow and Wetland Ecosystems Research Station of Lanzhou University, situated at 3500 m altitude on the Tibetan plateau. The experimental plots at the research station have an impressive natural biodiversity with up to 40 species in a single square-metre area. This ideal natural laboratory was manipulated for species richness by removing specific groups of species to enable a controlled study.

Professor Bradshaw explained that there are two principal theories regarding the biodiversity-disease relationship in non-human species: “One is that with more species there is a greater pool of potential hosts for pathogens, so pathogens increase as biodiversity increases. 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.”

Previous studies have primarily relied on data from planting experiments, limiting the conclusions that can be extended to natural communities. The ideal circumstances afforded by the Tibetan meadow plot resulted in a clear indication that biodiversity directly impacts disease resistance.

Professor Bradshaw described the results as “rather astounding”. He said, “The variation in disease severity at the different biodiversity levels almost exactly matched that predicted under the dilution hypothesis.”

As well as observing the overall incidence of fungal disease, the researchers also studied the impacts of nitrogen fertilisers and artificial warming on disease load, showing 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”.

The team asserts that this study provides additional evidence that the maintenance of biodiversity should be a high priority for the global community. Co-author Professor Zhou stated, “Changing the delicate balance of a healthy community not only resulted in more pathogens but weakened the overall community’s resistance to disease.”

This research was published in the journal Ecology.

Image credit: ©FreeImages.com/Frank Olthof