From: Victor Montoro, MONGABAY.COM, More from this Affiliate
Published February 20, 2015 08:45 AM

Biodiversity may reduce threat of disease

Biodiversity level changes can have consequences for species and habitats around the world. A new study published in the Proceedings of the Royal Society B, reaffirms previous findings that higher diversity in ecological communities may lead to reduced disease threat. The study concludes that higher amphibian diversity in the Brazilian Atlantic Forest is linked to a lower infection rate of a fungus that is devastating amphibian populations around the world.

According to the new study, biodiversity reduces the risk of the water-born fungus Batrachochytrium dendrobatidis (Bd), also referred to as chytrid fungus. Batrachochytrium dendrobatidis infection can lead to the disease chytridiomycosis in amphibians. Scientists believe it is transmitted both through direct contact among frogs and contact with infected water. The main symptom of the chytrid fungus is a thickening of the frog’s skin, which prevents the intake of nutrients and the release of toxins and may lead to death.

The geographic range of Bd is very widespread and has been found in Australia, Africa, the Americas, Europe, New Zealand and Oceania. The fungus is found even in pristine forests and high elevations, and scientists currently don't understand how it was spread. Some believe it may have been distributed with the trade of African clawed frogs (Xenopus laevis), which are common in labs around the world, while others think bullfrogs – which can carry Bd but aren't susceptible to infection – may be to blame. Still others think researchers themselves may have spread it while working in the field.

Amphibian populations are crashing around the world. Since the 1980s, declines have been ramping up, and species are going extinct at a pace at least 200 times the "background extinction rate," which is the rate at which extinction would naturally occur (some estimates place this rate much higher – at 25,000 to 45,000 times the background extinction rate). While scientists aren't sure exactly why this is happening, they suspect many factors may be to blame, from habitat destruction and out-competition by introduced species to exposure to ultraviolet radiation and pesticides. Batrachochytrium dendrobatidis is one of these suspects, and scientists have linked it to many amphibian declines and local mass extinctions. 

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Frog image via Shutterstock.

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