DNA from century-old museum jars revealed seven new frog species hiding in Madagascar

Some of the newest species known to science were sitting in glass jars for decades before anyone realized what they were. Researchers working through Madagascar’s population of small, burrowing frogs have identified seven previously unrecognized species, and they did it largely by extracting usable DNA from preserved museum specimens, some of which had been collected and shelved before the middle of the twentieth century.

A Genus Defined by Frogs That Look Nearly Identical

The frogs in question belong to Rhombophryne, a genus of small burrowing frogs found only in Madagascar’s forests and nicknamed “diamond frogs” for the angular, gem-like markings that appear on some species. The genus has long frustrated researchers because many of its species are visually near-identical to one another despite being genetically and behaviorally distinct, a problem known as cryptic diversity that makes traditional identification by appearance alone unreliable. With the addition of the seven newly confirmed species, the total number of recognized Rhombophryne species now stands at 27, nearly doubling what was known with confidence just a few decades ago. Madagascar as a whole is known for extraordinarily high rates of endemism, meaning many of its species exist nowhere else on Earth, a pattern that traces back to the island having separated from the African mainland tens of millions of years ago and evolved its wildlife in relative isolation ever since, which is part of why the island keeps producing new species discoveries even in groups of animals that have already been studied for well over a century.

Extracting DNA From Frogs Preserved Before 1976

To sort out which specimens actually represented distinct species, researchers combined three lines of evidence: physical measurements, recordings of each species’ distinctive call, and DNA sequencing recovered from both modern field collections and historical museum jars. According to the research summary describing the project, the team successfully sequenced DNA from the original name-bearing specimens tied to 23 of the 27 recognized species, a technically demanding feat given that preservation chemicals and decades of storage tend to degrade genetic material over time. For three of the species, researchers worked from specimens collected before 1976, meaning the DNA they recovered was old enough that extracting anything usable at all represented a genuine technical accomplishment rather than a routine lab procedure. Specimens preserved in formalin or older fixing chemicals common in early twentieth-century collecting practice tend to break genetic material down into short, damaged fragments over time, so researchers working with historical jars generally rely on techniques built for highly degraded samples, piecing together identifiable sequences from fragments too short to be useful with the standard methods developed for fresh tissue.

Why “Museomics” Matters for Species That Are Hard to Find

The approach of mining natural history collections for genetic data, sometimes called museomics, has become increasingly valuable for groups of animals that are difficult, expensive or logistically challenging to collect fresh specimens of in the wild. Madagascar’s diamond frogs live in forest leaf litter and burrow underground for much of their lives, making them hard to locate and observe compared with more visible amphibians, which is part of why so many of the genus’s species went unrecognized for so long despite specimens having sat in museum collections the entire time. By anchoring new species descriptions to genetic material from the original specimens collected decades or even a century ago, researchers can resolve naming disputes and taxonomic confusion that has accumulated over long stretches of scientific history. Every formally recognized species is anchored to a single physical specimen, known as the type specimen, which serves as the permanent reference point for what that species actually is, so confirming which museum jar corresponds to which name is not a bureaucratic formality but the foundation that the entire naming system depends on when a genus turns out to contain far more distinct species than its original description assumed.

What the New Species Tells Conservation Planners

Untangling how many distinct species actually exist within a genus is not just a matter of taxonomy for its own sake, since conservation status and protected-area planning are both built around species-level data. One of the newly named frogs, Rhombophryne quentini, was specifically cited in proposals to strengthen and expand protected forest areas presented at a planning workshop tied to Madagascar’s Biodiversity 30×30 program, a national initiative aimed at conserving a much larger share of the island’s remaining habitat. Researchers involved in the revision have also proposed that the large majority of the genus’s 27 species should be considered threatened, reflecting how heavily Madagascar’s amphibian diversity depends on forest habitat that continues to shrink under pressure from agriculture and logging. Because burrowing, forest-floor species like Rhombophryne rarely range far from a specific patch of habitat, losing even a relatively small area of forest can eliminate an entire species that exists nowhere else, which is why conservation planners increasingly want species-level data rather than broader genus-level estimates when deciding which forest fragments are worth prioritizing for protection.

A Genus Still Likely to Grow

Even with the count now at 27 species, researchers involved in the project have suggested the true diversity within Rhombophryne is probably still undercounted, since museomics and modern fieldwork continue to turn up genetic lineages that do not cleanly match any previously described species. Madagascar as a whole is considered one of the most biodiverse and least fully cataloged places on Earth for amphibians, and cryptic species complexes like this one are common across many of the island’s frog genera, not just this one. That means the seven newly described diamond frogs are likely to be followed by further additions as researchers continue applying the same combination of old museum specimens and new field genetics to other understudied groups.

This article was produced with AI assistance and edited by Morning Overview staff.

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