Black Salamanders Show Biodiversity of Redwood Forest

Estimating Gene Flow between Black Salamander Populations: a Multi-Locus Coalescent Approach

Large spotted A. flavipunctatus are found in southern inland Mendocino and Lake counties. Photo by M. Mulks
Large spotted A. flavipunctatus are found in southern inland Mendocino and Lake counties. Photo by M. Mulks

The range of the black salamander (Aneides flavipunctatus) almost perfectly overlaps with the historic range of redwoods along the Central and Northern California coast. While most animals live on the Earth’s surface, this well-hidden amphibian travels mostly up and down in the rocks and soil. Its vertical approach to life comes in handy when the weather is hot or dry: the salamander moves deeper into the Earth until conditions are more to its liking.

In Northwestern California, biologist Sean Bryant Reilly knew of another interesting adaptation of the black salamander: It is not always black. Along the coast, he found frosted ones to the north and solid black ones (or ones with tiny speckles) to the south. In inland areas to the south, “black” salamanders had big spots. The frosted ones in the north had 17 vertebrae and the solid and spotted ones in the south had 16. “So there is some kind of major break here,” Reilly said. “These populations have diverged quite a bit and might even be distinct species.”

Funded partly by Save the Redwoods League, Reilly decided to focus his Humboldt State University master’s thesis on a genetic analysis of these three populations in a Mendocino County area where all the color variations come together. “I wanted to see how much gene flow (interbreeding) there was among the different populations,” Reilly says.

In the end, Reilly found that the two southern populations were the most closely related genetically. But they hadn’t interbred with the other populations since they diverged a couple hundred thousand years ago. The two coastal populations—the frosted ones and the black or speckled ones—are still interbreeding, but only rarely. Reilly estimates that every three years or so, two individuals out of a population of hundreds of thousands interbreed.

Reilly’s data indicate that all three populations are likely separate species. Further analysis of the entire range is needed before any classification decisions are made, however. “By using new genetic methods, we can understand the true biodiversity in the redwoods,” he said. Otherwise, “we could be losing species without even knowing it.”

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