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Catalina Island rattlesnake may be a new subspecies

DNA studies aim to find if the venomous reptiles are distinct from the rattlers found around Southern California.

November 28, 2009|By Louis Sahagun

Could the rattlesnakes on Santa Catalina Island be a subspecies new to science?

DNA studies underway on five specimens -- four females and a male -- at Loma Linda University's Department of Earth and Biological Sciences aim to determine if they are distinguishable from the Southern Pacific rattlesnakes found in Southern California.

Naturalists have long suspected that the island's rattlesnakes behave differently, suggesting adaptations to evolving in isolation 22 miles from the Southern California coast.

For example, they are stouter and require more provocation to coil up and strike, said Carlos de la Rosa, chief conservation and education officer for the Santa Catalina Island Conservancy, a nonprofit organization that manages 88% of the 76-square-mile island as wilderness.

"In addition, the scale patterns on their heads are different, possibly indicating that they arrived thousands of years ago," he said. "Perhaps these differences are enough to justify declaring the Catalina rattlesnakes a new subspecies."

The rattler is the only venomous reptile on the island.

Conservancy naturalists suspect that the island also has several still-unclassified insect subspecies that adjusted to the peculiar landscape.

So far, scientists have identified 60 plant and animal species found on Catalina and nowhere else, including a tiny flowering rock cress and the Catalina Island fox.

That number is expected to grow.

"We've barely scratched the surface in terms of the variety of endemic species living on the island," De la Rosa said. "There's a lot of depth on this island left to explore."

Of particular interest is a species of Jerusalem cricket that is distinct from those on the mainland.

It hasn't yet been scientifically described -- or even named.

A year ago, researchers at USC examined genetic material extracted from Jerusalem crickets collected on the island and discovered two distinct groups within that subspecies, said Suzanne Edmands, an associate professor of biological sciences at the university.

"While finding a new subspecies of insect wouldn't be a huge surprise," she said, "finding two subspecies within 22 miles of the mainland is unusual."

A final determination will require studies of the "songs" the insects make when searching for a mate.

"Jerusalem crickets drum the ground with their legs," Edmands said. "So we really want to get more song data to see if they are drumming differently than those on the mainland, which would argue in favor of reproductive isolation."

louis.sahagun@latimes.com

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