Scientists have long debated whether the Florida panther is a North American cougar (Puma concolor couguar) or its own unique subspecies (P. c. coryi), ultimately settling on the former. The debate is part of a growing crisis in how scientists classify species. (Image credit: Maria Klos for Live Science)

LiveScience has an interesting article about a long standing debate in biology… “What defines a species?”  Biologist Ernst Mayr came up with one of the oldest definitions in 1942.  His biological species concept labels two organisms as different species, if they cannot reproduce and create fertile offspring.  Unfortunately, there are exceptions to this rule.

In 2016, scientists published a paper with a bold claim: that the giraffe, first described as a species by Swedish biologist Carl Linnaeus in 1758, might actually have been four species all along. Unlike Linneaus, the researchers had access to modern genetic tools, which revealed that giraffes fall into distinct clusters based on differences in their DNA, some of which are “larger than the differences between brown bears and polar bears,” the authors said at the time. 

The news sent ripples through the giraffe conservation community, which suddenly needed to protect four species instead of one. But from the start, there was disagreement about this new classification, and even today, the International Union for Conservation of Nature — an organization that oversees the listing of threatened and endangered species — lists the giraffe as a single species, Giraffa camelopardalis, with nine subspecies.