Iconic Joshua trees in race against extinction

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LAS VEGAS (AP) - A century from now, the Mojave Desert’s iconic plant could be pushing its way into new territory or teetering on the brink of extinction.

This spring, a pair of researchers will go looking for clues to the Joshua tree’s fate in a lonesome valley 140 miles north of Las Vegas. And they’re inviting interested “citizen scientists” to join them in their search.

Henderson-based ecologist Todd Esque, from the U.S. Geological Survey, and evolutionary biologist Chris Smith, from Willamette University in Salem, Ore., are offering a four-day course in March called “The Race North: Population Ecology of Joshua Trees In an Era of Climate Change.”

The class will unfold in Tikaboo Valley, near the Lincoln County town of Rachel, where Smith said Joshua trees seem to be “experiencing something of a population boom” at the northern limit of their current range, possibly in response to increasingly warmer, drier conditions to the south.

Such research matters, Esque said, because it could help scientists predict how much of a challenge climate change will pose for Joshua trees and for people. “We’re all in this together,” he told the Las Vegas Review-Journal (http://bit.ly/1dZG0AQ).

“Any time these large climatic events occur, some things blink out and some things survive and create new species,” Esque said. “If Joshua trees can respond quickly enough and spread their seeds far enough with each jump, they will continue to thrive out there.”

“It’s a population on the move as far as I’m concerned.”

Some computer models predict the Joshua tree could disappear from much of the Mojave Desert, as average temperatures rise and droughts grow longer and more frequent.

Smith said scientists have found evidence that the trees are already fading from parts of Joshua Tree National Park at the southern end of its range.

Tikaboo Valley serves as an ideal “natural laboratory” for studying the species because that’s where the two main varieties of Joshua tree - one from the east, the other from the west - come together and mix.

“It is possible to do a side-by-side comparison of which of the two plants are likely to win ‘The Race North,’ and how the reliance on specialized pollinators might limit their capacity to escape changing climate,” Smith said in an email.

This is his area of expertise. Smith has spent the past decade studying the highly specialized evolutionary bond between the Joshua tree and the tiny moth that pollinates it.

Each spring, yucca moths emerge from the ground to mate and lay eggs in the flowers of Joshua trees in Nevada, California and Arizona. But unlike bees and other insects that inadvertently spread pollen from flower to flower, these moths appear to deliberately pollinate Joshua trees so that the plants will produce seeds that eventually will feed the moth’s caterpillars when they hatch.

Simply put, the Joshua tree would not exist without the plain-looking moth about the length of a pencil eraser, and the moth would not exist without the tree.

Smith is studying how natural selection is involved in shaping this tight relationship between plant and insect - and whether their bond can live through climate change and the tree’s own race for survival. Last year, he received a prestigious, $850,000 grant from the National Science Foundation to continue his research for at least the next five years.

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