The world's newest flower is a species less than 140 years old hailing from southern Scotland, but its parents are from the Andes and North America's west coast. The yellow monkey flower, or Mimulus peregrinus—Latin for "wanderer," is described in the journal Phytokeys. (Click on the image for higher resolution.)

Mario Vallejo-Marin, a plant evolutionary biologist at the University of Stirling in Scotland, discovered M. peregrinus on a stream bank. Leaf and flower characteristics indicate its ancestors are M. guttatus and M. luteus, two species of monkey flowers transported from the Americas and cultivated by Victorian gardeners in the 1800s.

M. peregrinus's genus turns up around the world but most species grow in North America and Australia. Different monkey flower species can hybridize, although their offspring carry an odd number of chromosomes, rendering them sterile. "The classic example is if you cross a horse and a donkey, you get a sterile individual—a mule," Vallejo-Marin says. A rare mutation duplicated the entire genome of M. peregrinus. This polyploidic event evened out the number of chromosomes and the flower avoided a genetic dead-end.

"Theory predicted this plant would exist somewhere, and every time we came across a patch of hybrids, I would look," Vallejo-Marin says. On a trip with his family, he discovered a patch of hybrid flowers producing plenty of seeds. After analyzing the DNA, he confirmed the new species.

Several other species have cropped up this way over the past 200 years, but the recent discovery gives scientists a chance to watch the origin of a species as it happens. New genetic characteristics may arise as M. peregrinus spreads in the wild. The polyploidy is a "genomic revolution," says Vallejo-Marin, because the plant has twice the amount of genetic material it can use to adapt to changing environmental conditions. Adaptability gives invasive species their edge, he says, and could help life cope with climate change.

—Marissa Fessenden