It is raining lizards and geckos

Published: Thursday 31 December 2009

DownToEarthGlobal warming is good news for animal species that can manipulate their offsprings sex following changes in the temperature. A S Kallimanis, environment and natural resource management scientist at the University of Ioannina in Greece created a model on the impact of climate change on the geographical range of such species. He talks to Sharmila Kher

How was the model created?

Data on different species was collated from previous studies. Species whose sex determination is dependent on temperature (TSD) would respond to climate change by shifting their geographical range so as to reach their climatic comfort zone. The shift would be of two kinds either they would efficiently colonize adjacent habitats or face the possibility of extinction depending on where they are located in their species range.For example, species on the outskirts of their population would be able to move on better but those in the interiors would not be so lucky because high temperatures would restrict their population growth.

What would happen when the climate changes?

Down to Earth Under stable climatic conditions, populations of TSD species exhibit either of the three patterns more males are produced at low temperatures and more females at higher temperatures, more females at low and more males at high temperatures or females produced at both high and low temperatures, males at intermediate times. Availability of suitable nesting sites is also a limiting factor. When the climate changes, a rapid production of either males or females would lead to a balanced sex ratio and the growing population would move on to colonize new habitats.

Are all species equally equipped to deal with the change?

Initial research was limited to animals like turtles, lizards, geckos that are cold-blooded. I am working on a wider model that applies to warm-blooded animals as well.

How accurate is the model?

Down to Earth The model (published in Oikos on November 13) considers growth in small populations which are at the edge of their habitats. These have a small gene pool which might be an evolutionary roadblock. Another problem is the availability of new habitats. The juvenile inhabiting the new patch might also be a limiting factor depending on how well it survives in an unknown environment.

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