Yale Bulletin and Calendar

November 17, 2006|Volume 35, Number 11|Two-Week Issue

The mouse lemurs of Madagascar are the smallest known living primates.

Coat color may not be indicator of
species in lemurs, say researchers

Researchers have found that some lemurs, that might seem like they belong to different species because of their strikingly different coat colors, are not only genetically alike, but belong to the same species.

Historically, species classification has been based on comparison of visible physical characteristics of plants or animals. Kellie Heckman, a postdoctoral fellow in ecology and evolutionary biology at Yale, and her colleagues at other universities, used analysis of a mitochondrial gene, cytochrome b, to test the genetic relationship of 70 lemurs that were thought to belong to up to three different species. Their report was published in the open access journal BioMedCentral Evolutionary Biology.

"Our study combined morphological, genetic, geographic and ecological data giving a multidimensional, and hopefully more accurate picture of species diversity," says Heckman. "Over the past decade, the number of proposed species of these lemurs has jumped from 2 to 15, based on physical differences. It pointed to the need for caution when identifying new species solely on the basis of visual or genetic characteristics."

The lemurs they tested had three extremely different coat colors and lived in different types of forest locations in southern Madagascar -- classic characteristics of separate species. These researchers chose to compare mitochondrial cytochrome b as a gene marker that is known to change at a rate similar to that of speciation. Other common nuclear genes may evolve more slowly or more rapidly with population drift.

The researchers found that, according to the sequence of their cytochrome b genes, all belong to the same previously identified species, Microcebus griseorufus.

The authors' study also showed that lemurs with each of the three different coat colors could be found in all three geographical locations in similar proportions. They note that lemurs are nocturnal animals and tend to depend more on auditory cues or smell than on visual cues to recognize each other. They say that this could explain why a certain amount of variation in coat color does not affect species recognition in the mouse lemurs.

"There is a remarkable amount of diversity in primates," says Heckman. "We wanted to more thoroughly document this with both morphologic and genetic analysis."

Other authors on the article are Anne D. Yoder at Duke University; and Erica Machlin (a former Yale undergraduate), Emilienne Rasoazanabary and Laurie R. Godfrey at the University of Massachusetts. The work was supported by a National Science Foundation CAREER Award; a Biodiversity Leadership Award from the Bay & Paul Foundations; and grants from the Margot Marsh Biodiversity Foundation, Primate Conservation Inc., the American Society of Primatologists, and the Wenner Gren Foundation for Anthropological Research.

-- By Janet Rettig Emanuel

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Campus Notes