Plant Family Tree

Sequencing the DNA of every plant in Wisconsin is a daunting task, but a UW team recently accomplished just that. After four years, the project has now gathered information for some 2,600 species — from the most primitive fern to the most advanced flowering plants, plus conifers, birch trees, and more.

A dedicated group of botany professors and students built an evolutionary model of Wisconsin’s flowers, grasses, trees, and other plants. The effort, funded by a National Science Foundation grant, will contribute to a wider “tree of life” for all North American plants. It also provides clues about the origins of Wisconsin plants and their relationships to other species.

“We have some endangered species in Wisconsin that [have as] their very closest relative an invasive species,” says Ken Cameron, a UW botany professor and director of the Wisconsin State Herbarium. That information can inform conservation officials that invasive species could out-compete the rare species, or that hybrids could create “super weeds” that are resistant to chemicals.

Researchers, including botany professors Don Waller, Ken Sytsma, and Tom Givnish, used State Herbarium specimens, taking a square centimeter of leaf tissue to tease out two pieces of DNA from each species. They started with woody trees and shrubs, sequencing known native plants before moving on to invasive species. The oldest specimens were around 50 years old. A few species were collected in the field.

Wisconsin is the first state in the country to sequence its entire flora in this way, and the UW team hopes to map the results to see how species are distributed and interrelated. Preliminary mapping reveals a few surprises: some of the richest spots of plant diversity are not in remote areas, but instead are found in the heavily urbanized Fox Valley and places just north of Milwaukee.