It’s always in a researcher’s interests in this area to declare a new species, as opposed to an in-group variance:
At least hundreds of so-far unidentified species of mammals are hiding in plain sight around the world, a new study suggests.
Researchers found that most of these hidden mammals are small bodied, many of them bats, rodents, shrews, and moles.
These unknown mammals are hidden in plain sight partly because most are small and look so much like known animals that biologists have not been able to recognize they are actually a different species, said study co-author Bryan Carstens, a professor of evolution, ecology and organismal biology at The Ohio State University.
“Small, subtle differences in appearance are harder to notice when you’re looking at a tiny animal that weighs 10 grams than when you’re looking at something that is human-sized,” Carstens said.
“You can’t tell they are different species unless you do a genetic analysis.”Ohio State University, “Hundreds of new mammal species waiting to be found, study says” at ScienceDaily (March 28, 2022)
How do we know even then? Are the animals always tested as to whether they can mate with other similar groups and produce viable offspring before declaring them a separate species?
Look, it is probably true that hundreds of genuine species remain undetected. But in the absence of any rigorous standards for declaring a species, won’t claims like this be used merely for political purposes? Oh, and another paper: “Astonishing!: Separate species frequently hybridize!” Third paper: That’s a big problem! Give us money for extensive efforts to prevent it…. We need legislation…!”
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You may also wish to read: A physicist looks at biology’s problem of “speciation” in humans