Scientists have identified a previously unrecognized bird species in Japan after genetic research revealed that what was thought to be a single species is actually two species.
The discovery involves the Japanese warbler, a rare migratory bird found only on two island groups in Japan. New species of birds are described every year, but this case stands out because the birds look almost the same. Instead, DNA evidence provided the strongest evidence that they belonged to a different species.
“This shows how important it is to use genetic methods to uncover hidden biodiversity during a global biodiversity crisis. These methods can help provide a more complete knowledge on which to base future conservation efforts,” says Per Alström from Uppsala University, one of the researchers who discovered the new species.
DNA reveals hidden species
Japanese Warbler (Philoscopus ijimae) inhabit the Izu Islands south of Tokyo and the Tokara Islands approximately 1,000 km to the southwest.
Ten years ago, researchers first found evidence that the birds of the two island groups were genetically distinct. After analyzing the DNA sequence, they began an extensive investigation that included fieldwork on the island, study of museum specimens, and additional genetic research.
Whole-genome analysis ultimately revealed that the Tokara Islands’ bird population is significantly different from the bird species that inhabit the Izu Islands. Detailed comparisons of bird songs confirmed the genetic findings.
As a result, researchers from Uppsala University, Gothenburg University, and two Japanese institutions have officially described the Tocharian leaf warbler (leafmurotocharaensis) as a new species.
The discovery is particularly noteworthy because no newly described bird species has been confirmed in Japan since 1982, when scientists first described the Yanbaru rail.Galilaras Okinawae).
“This new species is a bit puzzling and difficult to define. In terms of appearance, it is no different from the common warbler. It is the DNA analysis and the differences in the song that indicate this is a different species,” Alström said.
Small population raises conservation concerns
Both species live on small islands and therefore have limited populations. The Tokara Islands span 12 islands, totaling just over 100 square kilometers, making the total land area smaller than Faroe (an island off the coast of Gotland).
Scientists have found that both species have very low genetic diversity. This can make them more vulnerable to environmental changes, habitat pressures, and disease. However, there are signs that the population may have made some recovery from previous declines.
Protecting two rare island birds
The brown warbler has already been designated as endangered by the International Union for Conservation of Nature, and is protected as a “natural monument” in Japan.
The newly recognized Tokara hedgehog appears to be at least as rare as the common hedgehog, leading researchers to recommend listing both species as Critically Endangered. They also say continued monitoring is important to detect future changes in populations and ensure the long-term survival of these rare island birds.
