(Santa Barbara, Calif.) UC Santa Barbara scientists trying to control the invasive tamarisk plant have been getting a boost from evolution, in the form of a rapidly evolving beetle that has been changing its life cycle to more efficiently consume the noxious weed. Their findings, in a paper titled "Evolution of critical day length for diapause induction enables range expansion of Diorhabda carinulata, a biological control agent against tamarisk," are published in the journal Evolutionary Applications.
"This is one of the clearest cases of rapid evolution," said co-author Tom Dudley, who is the principal investigator at UC Santa Barbara's Marine Science Institute Riparian Invasive Research Laboratory. The tamarisk leaf beetle, he explained, has managed to delay its entry into hibernation to adapt to the shorter days of the southern region of the United States. That adaptation in turn allows the beetle to survive until spring, while prolonging the time it has to reproduce, and increasing its effectiveness at controlling the invasive weed.
Also known as saltcedar, tamarisk is a shrub that was introduced to the United States from Eurasia in the 19th century. Since then, what was intended to be an ornamental plant has become a highly invasive weed, establishing itself in riparian areas and consuming valuable water supplies, as well as competing with native vegetation.
"It makes a lousy habitat for wildlife," said Dudley, adding that the plant is also a fire hazard, as it is highly flammable even when green and healthy.
However, the weed is an ideal home for the tamarisk leaf beetle, another Eurasian species that eats only the foliage of tamarisk and hibernates in its leaf litter. After almost a decade of testing, the insect was released into tamarisk-infested areas in 2001 by USDA and collaborating researchers, including Dudley and first author Dan Bean, who, at the time, was an associate researcher at UC Davis. T
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University of California - Santa Barbara