Japan: salamanders living proof of evolution


Hynobius kimurae

From Daily Yomiuri in Japan:

Darwin’s finches are world famous as examples of how new species emerge.

Lesser known, but equally valuable as evidence of speciation, are the many little Asian salamanders that live all over Japan.

The finches of the Galapagos diversified by adopting different behavior, but the Japanese salamanders split up chiefly through the process of isolation.

Salamanders are widespread throughout the temperate zones of the Northern Hemisphere.

Although they are sometimes confused with lizards, they are not reptiles at all, but amphibians with tails.

Tailed amphibians, which also include newts and sirens, number fewer than 400 species worldwide, as opposed to nearly 4,000 species for their close cousins, the frogs and toads.

With their squat bodies and short legs, salamanders retain the basic form of their distant ancestors, the first vertebrates to crawl out of the sea and colonize the land some 360 million years ago.

The Asian salamanders are thought to have originally evolved on the Asian mainland, and to have migrated into Japan during the glacial periods, when western Honshu and Kyushu were connected by land bridges to the Korean Peninsula.

These migrants from the continent found Japan much to their liking.

As they spread across the country, they first split into two groups.

One group stayed in the lowlands and river valleys, breeding in ponds, marshes and other bodies of still water.

The other group worked their way up into the mountains, breeding in faster-flowing streams and creeks.

Japan is a small country broken up by range after range of steep mountains.

As the salamanders spread eastward and northward, the populations in various valleys, as well as those living in various mountain ranges, became isolated from one another.

Unable to interbreed, these populations drifted away from each other genetically, eventually evolving into separate species.

Asian salamanders found Japan so much to their liking that the number of species here now outnumbers that on the continent.

In the genus Hynobius, for example, there are 28 species found worldwide, 16 of which live here in Japan.

Furthermore, 15 of these 16 species are endemic, which means that they can be found only in this country.

The Hida salamander (Hynobius kimurae, or hida sansho-uo) is a typical Japanese mountain salamander, an endemic species inhabiting the mountains of central and western Honshu.

Ogasawara islands south of Japan: here.

Japanese giant salamander: here.

Idaho giant salamanders in Montana, USA: here.

Anti-evolution religious creationism in Kenya: here.

Darwin’s frogs are also known as Darwin’s toads. The males play an important part in rearing the young, and have an unusual (and slightly alarming when first witnessed) brooding technique. They swallow their own tadpoles and then carry them around in their vocal sacs until they turn into froglets: here.

October 2010. Darwin’s frogs (Rhinoderma darwinii and Rhinoderma rufum) are native to Chile and Argentina and have a unique way they care for their young. Males take up eggs or newly-hatched tadpoles into their mouths. The developing larvae are maintained within the male’s vocal sac until he “coughs” up either tadpoles or fully formed juveniles. Both species of Darwin’s frogs are high on the list for conservation action: here.

6 thoughts on “Japan: salamanders living proof of evolution

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