Global climate change: The impact of El Nio on Galpagos mari...( New Haven Conn. A before-and-after ...)

New Haven, Conn. A before-and-after study led by Yale biologists, of the effects of 1997 El Nio on the genetic diversity of marine iguanas on the Galpagos Islands, emphasizes the importance of studying populations over time and the need to determine which environmental and biological factors make specific populations more vulnerable than others.

According to the authors, recurring El Nio events provide an ideal system to study the impact of human-mediated climate change on ecosystems worldwide, by allowing observation of changes in populations associated with individual events.

Since global warming is expected to cause an increase in the strength and frequency of El Nio events, it is important to evaluate the impact of El Nio on natural populations and their capacity to respond to environmental stresses, said Gisella Caccone, senior research scientist in ecology and evolutionary biology at Yale, and senior author of the paper published this week in the Public Library of Science (PLoS) One.

In this study, the researchers investigated the effect of sea surface warming associated with the single, intense El Nio event of 1997 to 1998 on genetic diversity in Galpagos marine iguana populations. They found that populations within the same species responded very differently.

Collaboration between German scientists who fortuitously collected and archived samples between 1991 and 1993 and Yale researchers who sampled the iguanas in 2004 enabled these unique before-and after comparisons. More than 800 samples from 11 Galpagos marine iguana populations were evaluated.

The researchers looked for changes in levels of genetic variation in nuclear microsatellite DNA and mitochondrial DNA markers of samples collected before and after this El Nino event. Changes in microsatellite frequency are sensitive enough to detect low p
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