DURHAM, N.C. The yellow monkeyflower, an unassuming little plant that lives as both a perennial on the foggy coasts of the Pacific Northwest and a dry-land annual hundreds of miles inland, harbors a significant clue about evolution.
Duke graduate student and native northern Californian David Lowry had become interested in how a single species could live such different lifestyles. He set out to find a gene or genes that would account for the monkeyflower (Mimulus guttatus) being a lush, moisture-loving, salt-tolerant perennial on the coast, but a shorter, faster-flowering, drought-tolerant annual inland.
What he found instead was that a large chunk of the plant's genome 2.2 million letters of DNA and 350 genes are working differently in each ecotype of the plant. The difference is called a genetic inversion, a long piece of DNA that has been clipped out of a chromosome at both ends and then reinserted essentially upside down.
"When you look at one plant species across a broad landscape with lots of different habitat conditions, you find differences in the genes from one place to the next," Lowry said. "The cause of these differences has been a source of contention among evolutionary biologists for decades as they've tried to figure out what mechanisms drive the origin of species."
A single species with a broad range of habitats like the monkeyflower can be expected to have a suite of genes available to help it adapt to the various conditions it would encounter within its range. But depending on where an individual plant finds itself, some of those genes aren't being used.
In the case of the monkeyflower, Lowry found that each ecotype has a large suite of adaptive genes carried within the inversion. The inland plants set about producing flowers and getting their reproduction done in the spring, before hot, dry weather arrives. The coastal plants grow a lot more foliage and flower much later without the threat
|Contact: Karl Leif Bates|