A team of U.S. scientists led by Chicago State University has analyzed species limits and diversification patterns in spotted skunks using nuclear and mitochondrial DNA datasets from broad geographic sampling representing all currently recognized species — Spilogale angustifrons, Spilogale gracilis, Spilogale putorius, and Spilogale pygmaea — and subspecies.
A spotted skunk doing its signature handstand. Image credit: Jerry W. Dragoo.
Spotted skunks — members of the genus Spilogale — are found throughout North America, but they haven’t made themselves at home in urban areas the way their striped cousins have.
Like their name suggests, these animals have spots instead of stripes — although technically they’re just broken stripes.
And while all skunks produce a nasty-smelling spray to deter predators, spotted skunks have the flashiest means of deploying it: they do a hand-stand on their front legs as an extra warning before they spray.
“Spotted skunks are sometimes called the acrobats of the skunk world,” said Dr. Adam Ferguson, a researcher in the Gantz Family Collection Center at the Field Museum.
Scientists have been interested in spotted skunks for a long time — the first species formally recognized was described in 1758 by Carl Linnaeus.
Over the years, as many as 14 species were recognized, though in recent decades that number’s been condensed to four.
“North America is one of the most-studied continents in terms of mammals, and carnivores are one of the most-studied groups. Everyone thinks we know everything about mammalian carnivore systematics, so being able to redraw the skunk family tree is very exciting,” Dr. Ferguson said.
In the study, Dr. Ferguson and colleagues analyzed DNA from 203 modern and museum specimens of spotted skunks.
Comparing the DNA sequences revealed that some of the skunks that had previously been considered the same species were substantially different.
“We found a high degree of genetic divergence among Spilogale that reflects seven distinct species and eight unique mitochondrial lineages,” the researchers said.
“Initial divergence between Spilogale pygmaea and all other Spilogale species occurred in the Early Pliocene (5.0 million years ago).”
“Subsequent diversification of the remaining Spilogale into an eastern and a western lineage occurred during the Early Pleistocene (1.5 million years ago).”
“These two lineages experienced temporally coincident patterns of diversification at 0.66 and 0.35 million years ago into two and ultimately three distinct evolutionary units, respectively.”
Among the new species described are the Yucatan spotted skunk, a squirrel-sized skunk found only in the Yucatan Peninsula, and the Plains spotted skunk.
“We’ve shown that the Plains spotted skunks are distinct at the species level, which means they’ve been evolving independently of the other skunks for a long time,” Dr. Ferguson said.
“Once something has a species name, it’s easier to conserve and protect.”
The team’s results were published in the journal Molecular Phylogenetics and Evolution.
Molly M. McDonough et al. Phylogenomic systematics of the spotted skunks (Carnivora, Mephitidae, Spilogale): Additional species diversity and Pleistocene climate change as a major driver of diversification. Molecular Phylogenetics and Evolution, published online July 22, 2021; doi: 10.1016/j.ympev.2021.107266