Amphibians have been disappearing from around the world at
an alarming rate. There is currently a global decline of amphibian populations,
which is affecting over 30% of amphibian species. (Stuart 2004) This enormous loss
of species is caused by a single disease: Chytridiomycosis.
The disease Chytridiomycosis is caused by the fungus Batrachochytrium dendrobatidis, which
attacks the layers of skin on the amphibian. It deprives them of oxygen, and is
currently a leading cause of death of frogs. The massive amount of death by Chytridiomycosis
is causing a huge loss of diversity of amphibian species. This leads to a
homogenization across the community of species where Chytridiomycosis is
present. A study by Smith et al. showed these exact results when studying Chytridiomycosis
in Costa Rica and Panama. The extinction rates at these sites were determined
to be nonrandom, due to the Chytridiomycosis. This disease also targeted mainly
riparian species, leading to riparian species loss and an increase in
terrestrial organisms. The amphibians were more similar at the family level,
creating more phylogenetic similarity. Smith et al. also determined that this
specialized extinction caused more species loss than a random extinction would.
This leads to an enormous loss of biodiversity, and could also reflect a loss
of amphibians at a global scale. As Chytridiomycosis continues to spread, there
could be a global extinction of certain amphibian species.
Smith, K. G., Lips, K.R., Chase J.M. (2009) Selecting for
extinction: nonrandom disease-associated extinction homogenizes amphibian
biotas. Ecology Letters 12: 1069-1078.
Stuart, S. N., J. S. Chanson, et al. (2004). "Status
and trends of amphibian declines and extinctions worldwide." Science 306:
1783-1786
Are amphibians evolving any defense mechanisms against this disease?
ReplyDeleteIs there any evidence for where this disease came from? As Aydan said above, what can be done to try and prevent further extinctions of amphibian species? Frogs are integral aspects of ecosystems, balancing insect levels and also acting as a food source for upper level predators.
ReplyDeleteDo the surviving amphibians possess any characteristics/mutations not seen in those that were killed by the disease? Did you come about any study that compared those that survived with those that did not? Evolution for these species towards a phenotype resistance against this disease is bound to occur, but this may take a long time.
ReplyDelete-Mary Morales
Is this affecting the Houston toad and leading to its decline?
ReplyDeleteAre certain amphibians more likely to get the disease than others? If so, it could be related to the environment.
Do you have any details on how they performed the study?
ReplyDeleteIs the evolution evident in a species that has become immune to the fungus? I'm also curious to know what effects the increase in terrestrial organisms are having/will have on the ecosystem.
ReplyDeleteThere is actually no known defense against this disease for wild populations, and no defense mechanisms observed so far. It was first observed in Australia in 1993, and so researchers wonder whether it originated from there or it was worldwide and virulence suddenly increased.
ReplyDeleteIn this study Smith et al collected specimens in Costa Rica before Chytrid was observed and then after it was observed, in several areas around the country.
Sources: http://www.pnas.org/content/95/15/9031.long
We commonly use evolutionary approaches to study and find treatments for human diseases, but have there been any attempts to use evolution to save these amphibians and preserve a niche of biodiversity?
ReplyDeleteAre there any current conservation efforts being put forward to stop the spread of this fungi? Either evolutionary as Tom pointed out, or otherwise?
ReplyDeleteYes, there seems to be ongoing research about how the protective coat on skin of a frog species blocks the disease agent: http://www.newscientist.com/article/mg20227115.300-probiotic-bug-is-a-frog-lifesaver.html
ReplyDeleteHow long has this fungus been attacking frogs? It seems as though the discovery is fairly recent, so perhaps frogs have time to become resistant to the fungus.
ReplyDeleteAmphibians include a pretty wide range of animals. Are all amphibian species equally vulnerable to this disease? Did the researchers keep track of which species suffered from infection or did they investigate just amphibians in general?
ReplyDeleteMan this sounds terrible!! What are they doing to try and combat the disease and to try and preserve biodiversity in amphibians?
ReplyDeleteThis sounds extremely sad. Is there any way to cure frogs and other amphibians once they are infected with chytrid?
ReplyDelete