Mountain streams harbor salamanders found nowhere else, separated by ridges for millions of years. Genetic divergence between adjacent valleys approaches species-level differences.
The divided valleys
Jirisan National Park, designated as South Korea's first national park in 1967, is a mountainous refuge of biodiversity. Its rugged topography, with the peak of Cheonwangbong reaching 1,915 meters, creates a complex network of deep valleys and sharp ridges. This landscape is a natural laboratory for evolution, particularly for amphibians with limited dispersal abilities. The mountain's streams host several species of salamander from the family Hynobiidae, including the Korean clawed salamander, Onychodactylus koreanus.
These salamanders are highly sensitive to their environment, requiring cold, highly-oxygenated water found in forested mountain streams. The steep ridges of Jirisan effectively act as impassable barriers, isolating salamander populations within their respective valleys. Over long periods, this geographic isolation prevents gene flow between populations in adjacent valleys. As a result, these isolated groups have embarked on their own distinct evolutionary paths. This process, known as allopatric speciation, is visibly at work in Jirisan, where populations separated by just a few kilometers of high terrain show significant genetic and morphological differences.
A laboratory of evolution
The genetic separation between Jirisan's salamander populations is not trivial. Studies on the genus Onychodactylus reveal deep evolutionary splits. For example, the recently described Onychodactylus sillanus, found in the southeastern Korean Peninsula, diverged from its sister species, O. koreanus, approximately 6.82 million years ago. This level of divergence is substantial, demonstrating how long-term isolation has produced unique evolutionary lineages. Within the park, different valleys harbor genetically distinct populations of O. koreanus, with variations so pronounced they are considered candidate species, nearly becoming entirely new species.
The salamanders of the genus Hynobius also show this pattern of diversification across the Korean Peninsula. All Hynobius species on the peninsula form a single monophyletic group, suggesting they diversified after becoming isolated there. The physical barriers of Jirisan have accelerated this process locally. Researchers can identify which valley a salamander comes from simply by analyzing its mitochondrial DNA. These living experiments in evolution make Jirisan an important location for understanding the mechanisms of speciation and the effects of geographic barriers on biodiversity.
💡Fun Facts
The Korean clawed salamander (*Onychodactylus koreanus*) is named for the black, claw-like keratinous structures on its fingertips, an adaptation for navigating fast-flowing mountain streams.
Another salamander found in Korea, the Korean crevice salamander (*Karsenia koreana*), belongs to the family Plethodontidae. It is the only known lungless salamander in Asia and breathes entirely through its skin.
The larval period for some clawed salamanders can last for over two years before they undergo metamorphosis into their adult form.
The Korean clawed salamander has two distinct breeding seasons each year: one in the spring (April-June) and another in late autumn and early winter (November-December).
The park is open year-round, but hiking hours are restricted based on season (e.g., from 4:00 AM in winter and 3:00 AM in summer), with climbers needing to start their descent from peaks by early afternoon.
Admission
Free admission to the park itself, though some temples located within the park grounds may charge a separate cultural heritage entrance fee.
Accessibility
The terrain is mountainous and consists of rugged, rocky trails. Most routes are not wheelchair accessible. Some easier, paved paths exist near visitor centers, like the trail from Seongsamjae Rest Area to Nogodan.