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Researchers from three universities have measured more than 19,000 moths out of 1,100 species to determine if their size varies with altitude. Scientists from the Friedrich-Schiller University of Jena (Germany) collaborated on the study with colleagues from Marburg in Germany and Connecticut in the United States. "The size of the body plays a central role in the ecology and evolution of organisms," says Dr. Gunnar Brehm of the University of Jena. The zoologist is the lead author of the study, which has just been published online.
The temperature-size rule applies
"The vast body of data from a hotspot of biodiversity sets new standards because never before has a study been conducted with as many species on a full elevation gradient , from the lowland rainforest to the top of a volcano in Costa Rica, "said Brehm. The researchers found clear patterns in their measurements: butterflies belonging to two families extremely rich in species (Arctiinae (tiger butterflies) and Geometridae (surveyors)) grow considerably at higher altitudes. This corresponds to the expectations of what is called the "Bergmann rule". However, this rule was initially only provided for birds and mammals, and it is different for cold-blooded animals such as insects. "We had actually assumed that these animals would become smaller at higher altitudes.With a lower wing load to carry, the butterflies better able to withstand leaner air in flight," adds Brehm. "However, in fact, the load is clearly increasing, and with the increasing altitude, ecosystems are becoming less productive, which should favor small species." Other factors obviously play a more important role: the "temperature-size rule" predicts that at lower temperatures, animals reach a larger size. The researchers were able to demonstrate this trend, not only in different species, but also within species.
With the new data, the research team has created a foundation for experimental approaches to better understand functional relationships, including in complex and species-rich ecosystems, particularly with a view to global warming.
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