Today, despite a startling ability to produce genetically customized variations of itself to fit almost any ecological niche, the silversword — actually a group of closely related plants known as the silversword alliance, unique to the Hawaiian Islands — is an endangered species.

Research on plant evolution by Dr. Michael Purugganan of North Carolina State University’s College of Agriculture and Life Sciences’ Genetics Department might be applied to understanding the silversword’s problems.

Purugganan’s work, funded in part by the National Science Foundation, as well as his work with a more prosaic plant — the cauliflower — holds other major implications for agriculture.

“Where we come in is in isolating the regulatory genes that control a plant’s flowering structure,” says Purugganan. “Our studies give us a genetic snapshot of plant evolution. And if we learn how new plant structures arise, if we know how nature breeds new plants, we might extrapolate if we want to breed new crops.”

Purugganan’s research group wants to know how much molecular variation there is in flower developmental genes within populations, what evolutionary forces pattern this variation and whether the variations contribute to the organism’s diversity as it reacts to its environment.

“After all,” Purugganan notes, “crops are plant species that evolved in a cultural context to provide food and other products for human society. They are fascinating subjects for evolutionary study since they are examples of species that have undergone rapid diversification under intense selection pressures, as has the silversword. And they help us understand the dynamic interfaces between genetics, evolution and human culture.”

Purugganan’s recent article for Genetics magazine addresses one of several questions surrounding domestic plant development.

“How did Neolithic farmers select plants for development?” he asks. “What were they doing to those plants’ genetics, although without realizing they were selecting genes?”

In other words, why do we eat cauliflower and its relatives — kohlrabi, kale, brussels sprouts, broccoli and other cabbage family members — rather than some variety of, say, cactus?

“What we know,” Purugganan says, “is that primitive farmers, probably Romans, as early as 600 B.C. selected cauliflower and its relatives by stopping their development. They inhibited flower growth by unknowingly selecting for a ‘stop mutation’ gene. When the early farmers were selecting cauliflower, they also were selecting for this mutation.”

What we actually eat from those plants, he says, are structures that were on the verge of turning to flowers, but were nipped, so to speak, in the bud.

Among several other distinct but interrelated ongoing projects at Purugganan’s lab is the study of island species such as silverswords that have undergone much more recent, but exceptionally rapid adaptive diversification.

“Hawaii is the most isolated land mass in the world, yet the silversword, its state flower, has produced more than 30 species that look so different from one another that nobody realized until recently that they were all related,” he says.

Around six million years ago, mainland U.S. ancestors of the silversword, a tarbush found in the Sierra Nevadas of California, appeared on and colonized the first lava islands in northern Hawaii. As they invaded different islands, they adapted to different environments: bog, desert, scrub, mountains. And each habitat was home to a new species.

But even prolific plants fall to the encroachment of humans, who introduced sheep and other silversword-munching animals to the islands.

Purugganan hopes his work will help save the silversword, even if indirectly.

“We’re isolating and studying genes from the silversword alliance, members of which possess spectacular differences in flowering cluster forms between closely related species,” he says.

“We hope to identify genes responsible for naturally occurring variations in flower-cluster architecture and dissect the evolutionary forces that act at these genetic loci.”