Friday, September 30, 2011

How Biodiversity Loss May Be Elevating the Impact of a Fatal Fungal Infection in Amphibians

        The early 1990s heralded a growing concern over the declining amphibian populations worldwide.  There was much uncertainty about whether population declines were due to environmental fluctuations causing high mortality locally in some amphibian populations, or an ulterior cause (Wake 1991).  After a history of over 100 million years on the planet, conservation biologists were concerned yet intrigued by the sudden decline in these populations.  A later study found a fungus had induced epidermal changes in dead amphibians found during mass mortality events in Australia and Panama (Berger et al. 1988). Perhaps some of you have heard of the deadly chytrid fungus, Batrachochytrium dendrobatidis? Amphibian mortalities from this fungus have continued over the past decades, leading scientists to investigate any and every means to conserve amphibian species, many of which are essential top predators in food chains across a range of habitats.  Not only are these organisms at risk from a deadly fungus, but habitat destruction, climate change, and chemical contamination are also threats.

         Unfortunately, things aren’t going well for the amphibians. However, a recent study unveiled one piece of information critical to the preservation of amphibian species. Researchers from Oregon State University have found that loss of biodiversity may be elevating the impact of the fungal infection B. dendrobatidis decimating amphibian populations worldwide (Searle et al. 2011). Why? Having greater diversity reduces disease transmission via “dilution”—some species are not ideal hosts for the fungus, or are not susceptible at all. Therefore, it is key that conservation ecologists work not only to reduce mortality of species vulnerable to infection, but to also focus on maintaining high biodiversity. Though studies have shown that ecosystem function can be retained with relatively few species, this study highlights just how important biodiversity can be.  If high biodiversity is maintained, organisms will be less susceptible to epidemics that could endanger many species and deteriorate ecosystem function.

Berger, L. R. Speare, P. Daszak, D. E. Green. A. A. Cunningham, C. L. Goggin. R. Slocombe. M. A. Ragan. A. D. Hyatt, K. R. McDonald, H. B. Hines, K. R. Lips, G. Marantelli, and H. Parkes. (1998) “Chytridiomycosis causes, amphibian mortality associated with population declines in the rain forests of Australia and Central America”. Proceedings of the National Academy of Sciences of the United States of America 95:9031-9036

Wake, D.B. (1991) “Declining amphibian populations”. Science 253, 860

Oregon State University. "Biodiversity loss may be contributing to amphibian-killing fungal infection." ScienceDaily, 20 Sep. 2011. Web. 30 Sep. 2011.

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