May 18, 2009

Good News and Bad News About Amphibian Diversity

The number of known amphibian species worldwide has risen by approximately 20% during the the past decade thanks to intense research on this group of vertebrates. A total of 6487 amphibian species have been described to date ( That is the good news.

Now here comes the bad news. Based on a study published in 2004 in the journal Science, more than 40% of the world's amphibians are threatened with extinction. Given the current number of amphibian species (6487), that means that more than 2500 amphibian species are in serious decline. However, a study by Vieites and colleagues just published in the Proceedings of the National Academy of Sciences suggests that the number of described amphibian species vastly underestimates the actual number of amphibian species on Earth. That means that far more species are in danger of extinction than previously believed.

Vieites and colleauges used DNA sequences from 2850 amphibian specimens sampled from over 170 localities in Madagascar to show that the current number of described amphibian species
(244) in this biodiversity hotspot represents only about one-half of the actual number of species present (estimated actual number of species is 373-465). Therefore, hundreds of species remain undescribed. Habitats on Madagascar have been badly degraded by deforestation, and the results of the new study suggest that this has caused the extinction of far more species than have so far been documented. Furthermore, to date Madagascar is still free of the amphibian chytrid fungus. When the fungus does invade, it won't be 244 species that are impacted. It will be 373 to 465.

The more we learn the bleaker the prospects seem for conserving even a fraction of the Earth's amphibian biodiversity.

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