Biologists have long sought to classify living things and understand how they are related. In the 1700s, Swedish naturalist Carl Linnaeus came up with a system of classifying organisms. You probably learned about this system in school – remember “King Philip Came Over For Grape Soda?” That was a mnemonic to help you learn Linnaeus’s taxonomic categories of Kingdom, Phylum, Class, Order, Family, Genus, and Species. Those classification categories are still used today, almost 300 years after Linnaeus first introduced them.
Since then, although biologists all concede that species are real, identifiable entities, they have fiercely debated how to define a species. After all, it is hard to come up with a definition for a species that would apply to such distantly related things as birds and bacteria. Most biologists also believe that although categories above the species level are useful for categorizing living things, they are not biologically meaningful and therefore cannot be defined.
Dr. Amy Baird (UHD Professor of Biology) and her colleagues recently published a paper in the journal PLoS One that seeks to change the attitude of biologists toward the meaning of taxonomic categories above the species level. In this paper, they proposed a definition for a genus, which they called the “2 Sigma Genus Concept.” Basically, the concept defines a genus based on the amount of genetic differences of closely related organisms. They tested their idea using groups of bats.
“We have studied tree bats in my lab at UHD for about 10 years,” says Baird. “Some of our early findings indicated that these bats were more diverse than initially thought, so we split what was one genus of bats into three. Other scientists debated this conclusion, which led us to think about how we could make a genus something testable and meaningful.” Their results, described in the paper, demonstrated that their proposed classification of these bats into three groups was more in line with their definition of a genus than keeping them grouped into just one genus. Baird and her colleagues believe that this paper will have a positive impact on the science of taxonomy and lead to higher levels of taxonomic classification becoming categories that have biological meaning and able to be standardized across living things.