Friday, March 6, 2009

Salamaders and climate change -impending extinctions?

ResearchBlogging.orgBy the now the evidence of a global frog decline, perhaps even an extinction crisis, has been well documented. But what about salamanders? They are normally less abundant and less-studied compared to frogs, but is there evidence of the same general pattern of declining population sizes? According to Sean Rovito and colleagues, the answer is unfortunately yes. They repeated a plethodontid (lungless) salamander survey done in the 1970’s in Central America and found that many species have declined. In fact they failed to find a couple of previously very abundant species. They also found that species declines were phylogenetically non-random and so these declines may result in the loss of whole clades of species, meaning that the evolutionary history of these salamanders is at risk.

The authors attempted to determine the cause of these declines and found that neither habitat loss or the chytridiomycosis fungal disease implicated in other declines explained these salamander declines. The authors hypothesize that these declines are a direct result of climate change –namely changing temperature and humidity. If so, we may be witnessing some of the first extinctions that are directly caused by climate change.

S. M. Rovito, G. Parra-Olea, C. R. Vasquez-Almazan, T. J. Papenfuss, D. B. Wake (2009). Dramatic declines in neotropical salamander populations are an important part of the global amphibian crisis Proceedings of the National Academy of Sciences, 106 (9), 3231-3236 DOI: 10.1073/pnas.0813051106

Post script:
We had a comment questioning the use of climate change as an explanation and here is my response.

Science works by finding parsimonious explanations, until through experimentation or observation another, better explanation emerges. The previous explanations of habitat loss or fungal infections were not supported. These habitats, known as cloud forests, are very humid. The lungless salamanders have no lungs and instead breath through their skin, which must be kept moist. These forest are becoming drier, hence the probable connection. Here's a quote from the paper:

"Pounds et al. (25) used modeling to show that largescale warming led to a greater decrease in relative humidity at Monteverde compared to that caused by deforestation. Species of cloud forest salamanders that can still be found rely at least
in part on bromeliads. Bromeliads depend on cloud water deposition and are predicted to be articularly vulnerable to climate change (26, 27)."

Doesn't sound like "magic" to me, rather a robust hypothesized mechanism worthy of more testing. Given that species are going extinct, it is important to suggest likely mechanisms, providing an impetus for more research.

For those that think that scientists use climate change as boogey man to scare up more research funding (i.e., Crichton), please read the science. You'll discover honest, hardworking folks that are trying to understand this changing world and whose research can only benefit you , me and the salamanders.

6 comments:

Anonymous said...

So because they can't find a reason for not knowing why they have a different result, they invoke the magic of "climate change".

Marc Cadotte said...

Science works by finding parsimonious explanations, until through experimentation or observation another, better explanation emerges. The previous explanations of habitat loss or fungal infections were not supported. These habitats, known as cloud forests, are very humid. The lungless salamanders have no lungs and instead breath through their skin, which must be kept moist. These forest are becoming drier, hence the probable connection. Here's a quote from the paper:

"Pounds et al. (25) used modeling to show that largescale warming led to a greater decrease in relative humidity at Monteverde compared to that caused by deforestation. Species of cloud forest salamanders that can still be found rely at least
in part on bromeliads. Bromeliads depend on cloud water deposition and are predicted to be articularly vulnerable to climate change (26, 27)."

Doesn't sound like "magic" to me, rather a robust hypothesized mechanism worthy of more testing. Giving that species are going extinct, it is important to suggest likely mechanisms, providing an impetus for more research.

For those that think that scientists use climate change as boogey man to scare up more research funding (i.e., Crichton), please read the science. You'll discover honest, hardworking folks that are trying to understand this changing world and whose research can only benefit you , me and the salamanders.

trav said...

just an aside and question: salamanders are the most abundant vertebrate in southern appalachian forests... i don't think anybody ever used the throughfall disaplacement experiment (TDE) on walker branch at ornl to investigate how salamanders responded to 33% increase or decrease in precipitation. i've email paul hanson to ask him. would be an interesting experimental test of how altered climate influences salamanders.

travis belote

p.s. i love this blog

Marc Cadotte said...

Good idea Travis, it would be valuable to see experimental tests, where potential mechanisms are manipulated. Let me know what comes of it.

Anonymous said...

No luck; no one bothered to sample salamanders at the TDE. Paul said that because the TDE was on a "drier SE aspect that it wasn't likely to be a major habitat anyway"... With lots of respect, I don't buy it. The sites I worked on in the Jefferson NF have southerly exposures with more well-drained soils and still supported ~1 salamander every few square meters. The TDE has been decommissioned, so there's no chance of investigating the question there. I think this was a missed opportunity.

dee em said...

Science works by finding parsimonious explanations, until through experimentation or observation another, better explanation emerges. The previous explanations of habitat loss or fungal infections were not supported. These habitats, known as cloud forests, are very humid. The lungless salamanders have no lungs and instead breath through their skin, which must be kept moist. These forest are becoming drier, hence the probable connection. Species of cloud forest salamanders that can still be found rely at least in part on bromeliads. Bromeliads depend on cloud water deposition and are predicted to be particularly vulnerable to climate change. It "Doesn't sound like "magic" to me, rather a robust hypothesized mechanism worthy of more testing. Giving that species are going extinct, it is important to suggest likely mechanisms, providing an impetus for more research. For those that think that scientists use climate change as boogey man to scare up more research funding (i.e., Crichton), please read the science. You'll discover honest, hardworking folks that are trying to understand this changing world and whose research can only benefit you , me and the salamanders.