The poison frog that fooled scientists for decades
Scientists at the University of Kansas Biodiversity Institute and Natural History Museum recently uncovered a mistake that dates back
Scientists at the University of Kansas Biodiversity Institute and Natural History Museum recently uncovered a mistake that dates back decades involving a poison frog specimen from Peru. The frog had been incorrectly identified and designated as a holotype, which is the single preserved specimen used to officially define a species. While modern taxonomy may also rely on supporting materials such as photographs or genetic information, the holotype remains the primary reference point.
The research team published its findings in the journal Zootaxa.
Why Holotypes Matter in Species Science
“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.”
This system ensures that scientists around the world are referring to the same organism when discussing a species.
A Photo, a Catalog Number, and a Critical Mix-Up
The error traces back to 1999, when a researcher encountered a published photograph of a brightly colored frog from the Peruvian rainforest near the Ecuadorian border. Unable to match it to a known species, he described it as new using only the photograph of a specimen housed in the University of Kansas herpetology collection. The frog was logged under specimen number KU 221832 and given 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.”
How the Error Was Discovered
The problem came to light years later when herpetologists visiting the Biodiversity Institute asked to examine the holotype while studying related frog species.
“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.”
That discovery prompted Motta and her colleagues to investigate how the mistake occurred.
Scientific Detective Work in Museum Records
“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.”
By carefully reviewing historical documentation, the team was able to link the original photograph to the correct frog specimen.
Reclassifying the Frog Species
As a result of the correction, the frog once described as Dendrobates duellmani is no longer considered a separate species. It is now recognized as a color variant 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.”
Rethinking What Defines a Holotype
Motta said the case highlights the critical role of natural history collections and raises questions about how holotypes should be defined today. With species disappearing faster than scientists can formally describe them, there is growing pressure to name species using incomplete 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.”
Why Photos Alone Fall Short
Even so, Motta emphasized that relying solely on photographs is not ideal.
“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,” she 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.”
A Rewarding Resolution
Correcting the mistake brought a sense of satisfaction to Motta, especially since the error had been cited repeatedly in research for more than 20 years. She oversees the world’s fourth-largest herpetology collection.
“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.”
