The meticulous classification of organisms into distinct species forms the cornerstone of modern biology. However, the criteria used to differentiate one species from another are surprisingly fluid. Scientists have employed at least 26, and potentially as many as 54, different definitions to describe the estimated 8.7 million species that exist today. This number is constantly fluctuating as new evidence prompts adjustments or reclassifications of species. Single species are often split into multiple entities, while seemingly distinct species sometimes turn out to be variations of the same. Even popular and well-established animals like the African elephant and the orca have undergone scrutiny, revealing unexpected complexities in their taxonomic identities. Here are six instances where scientists initially misjudged species classifications:
For centuries, the manta ray was universally considered a single species. In 2009, however, University of Queensland graduate student Andrea Marshall published research differentiating the manta ray into two distinct species – the giant, or oceanic, manta ray ( *Manta birostris*) and the reef manta ray (*Manta alfredi*) – based on consistent differences in their physical appearance. At the time, Marshall hinted at the possibility of a third species, and in 2020, researchers corroborated her claim. While this new species has not yet received formal recognition, it is informally known as the Caribbean manta ray.
Deep within the Florida Everglades, lucky visitors might catch a glimpse of the state’s largest and most endangered cat – the Florida panther. Smaller than a typical cougar and possessing a kinked tail attributed to inbreeding within a shrinking population, the Florida panther has been a source of controversy since its discovery in 1896. Throughout the 19th and 20th centuries, scientists wavered between classifying the Florida panther as simply another North American cougar (*Puma concolor*) and granting it its own unique subspecies designation (*Puma concolor coryi*). In 2017, as part of a global initiative to standardize the taxonomy of the world’s felines, the Cat Classification Task Force opted for the former, classifying all cougar populations in North America as *Puma concolor*.
Coral reefs stand as some of the most biodiverse habitats on Earth. Every square inch is occupied, and every scrap of food is consumed. This intense competition for space and resources drives species to diversify in order to find new niches to exploit. This phenomenon, known as adaptive radiation, can spawn thousands of new species, many of which display striking differences in appearance. In other cases, however, species may appear so similar that the only way scientists can distinguish them is by examining their DNA – a form of hidden biodiversity known as cryptic diversity. In a study published in February, scientists discovered that the DNA of a single species of tiny, sponge-dwelling fish called a goby contained seven distinct genetic lineages that may represent new species, according to senior/co-author Andrew Gracey, a molecular ecologist at the University of Texas at Austin’s Marine Science Institute.
The African elephant was once believed to be a single species. In 2021, however, it was divided into the African savanna (or bush) elephant (*Loxodonta africana*) and the African forest elephant (*Loxodonta cyclotis*). While scientists acknowledge that subdividing species into increasingly granular groups can pose challenges for conservationists in directing resources, the African elephant exemplifies how new data can actually simplify the process. The International Union for Conservation of Nature (IUCN) – an organization responsible for listing threatened and endangered species – had previously classified the single African elephant species as vulnerable. However, splitting the group elevated the African forest elephant to critically endangered status, paving the way for enhanced protections. Following population declines exceeding 86% over the past 30 years, certain African forest elephant populations have shown signs of recovery thanks to stringent anti-poaching measures.
The orca, or killer whale, serves as a well-known example of speciation occurring in real time. While all of the estimated 50,000 orcas alive today are currently grouped into a single species (*Orcinus orca*), there are at least nine distinct populations, each with its own unique appearance, behavior, and habitat. Resident killer whales, for example, tend to have smaller home ranges and specialize in consuming fish, while transient orcas travel vast distances and prey on seals and other whales. These populations are currently diverging to such an extent that they struggle to communicate with each other or reproduce, leading some scientists to propose that the orcas should be split into multiple species.
When renowned Swedish biologist Carl Linnaeus first described the gangly, bizarre-looking giraffe in 1758, he assigned it to the genus *Camelopardalis*. However, his classification of the giraffe as a single species (*Camelopardalis giraffa*) persisted for centuries. It wasn’t until 2016, when scientists gained access to cutting-edge genetic tools, that they realized the roughly 120,000 giraffes alive today may actually represent four distinct species. Their suggestion was contentious at the time and remains so today. The IUCN, for instance, continues to list the giraffe as a single species with nine subspecies.
