A clerical error caused misidentification of frog specimen that once stood for an entire species

LAWRENCE — Researchers at the University of Kansas Biodiversity Institute and Natural History Museum recently uncovered a slipup from decades ago: the misidentification of a poison frog specimen from Peru used as a holotype. A holotype is an individual preserved specimen collected in the field and deemed to officially represent an entire species — though today, scientists sometimes use associated data like photos or genetic data as part of the holotype.

Their findings were published in the journal Zootaxa.

“When you describe a species, you assign one specimen that bears the name of that species,” said lead author Ana Motta, collection manager of herpetology at the Biodiversity Institute. “If I find something else later that looks like that species, I need to go to the holotype and compare things to know if that new population belongs to that species or is something else. So, the holotype is the specimen that represents the species.”

In 1999, a researcher saw a published photo of a colorful frog from the Peruvian rainforest, near the Ecuador border. Unable to identify its species, he described the mysterious frog based on that single photo of a specimen previously deposited with KU’s herpetology collection, recording it as specimen KU 221832 and bestowing it with the scientific name Dendrobates duellmani.

“Each specimen gets a catalog number. It’s like a barcode,” Motta said. “All photos, genetic data, calls, whatever we have associated with that specimen are linked to that catalog number. When the researcher saw the photo, instead of asking for the specimen, they asked for just the catalog number, and they were given the wrong catalog number that belonged to another specimen. So, they associated the wrong specimen with the new species description. The true specimen was real. It just had another catalog number.”

When herpetologists recently performing research at the Biodiversity Institute requested to examine the holotype, the error was discovered.

“We had visitors — experts in this frog group — studying many species,” Motta said. “Because the holotype represents the species, they wanted to look at the holotype to understand other populations. When they got the specimen with the described number, they realized: This is not it. The frog is very colorful, and the numbered one was brown.”

Soon, Motta and her colleagues were engaged in a hunt for clues about how the error occurred in the first place.

“We went through field notes and photo records,” Motta said. “We started matching all kinds of data — what photo belonged to what specimen. We found the correct specimen that was pictured in the photo and made the correction based on that.”

In the end, the frog in question has since been reclassified, and it’s no longer deemed to be an independent species. Today, Dendrobates duellmani rather is classified as an example of the Amazon poison frog, Ranitomeya ventrimaculata.

“With more data, we are describing more species — hidden biodiversity that looks alike but is genetically different,” Motta said. “But the opposite happens, too: Things that look different morphologically can be the same species genetically. That’s what happened here. The populations have different colorations but are not reproductively isolated. They share a lot of genetics. They are one species, just with variation. You have extremes, and when you keep collecting, you find a spectrum.”

Motta said the detective work shows the importance of natural history collections and calls for a reexamination of what constitutes a holotype. Because species are going extinct more rapidly than scientists can describe them, she said, there’s pressure to describe species sometimes using less-than-complete information.

“We’re in a new era of collections,” Motta said. “Before, you’d think about a holotype as just the physical object — the animal itself. Now we have the ‘extended specimen.’ All the data and parts associated with that specimen are part of the specimen. The holotype includes the genomic data if that’s available. For example, when you describe frogs, you can use calls. Frogs have species-specific calls. All that belongs to the holotype. It’s part of the holotype.”

However, the KU researcher said basing a holotype on a photo alone isn’t an optimal approach.

“It’s important to actually work with the specimen itself because specimens are the way that you can confirm things. That research can be reproducible,” Motta said. “The problem occurred because the description was based on a photo. That’s not the best practice. There are discussions on that: Should we be able to describe species based on photos? Having the specimen is the only way you can reproduce or verify data. Data must be verifiable and reproducible. A photo is limited.”

Motta said sorting out the frog confusion, which had been carried forward for over two decades as the error had been cited and reproduced in follow-up research, was a fulfilling moment in her career running a natural history collection, especially as the herpetology division she oversees is the world’s fourth-biggest.

“This is what got me interested in being a collections manager,” she said. “It’s very satisfying, a puzzle. Collections are dynamic and full of new discoveries. There is still so much to understand.”