Natural historians worry about threat foreign plants pose to environment

Allison Remcheck

Honeysuckles and rambler roses are taking over — and native plants are becoming extinct.

Oscar J. Rocha, assistant professor of ecology, studies the evolution of these invasive species.

Rambler roses, or the multiflora rose, and honeysuckles, were brought to the United States from Asia between the 1930s and the 1960s, Rocha said, “And then they escaped and started growing out of control.”

Birds dispersed the seeds of these plants first planted in ornamental gardens and caused them to grow everywhere, Rocha said.

“Now they are all over and people think that they were native, but they were not,” he said. “They were introduced.”

Rambler roses, in particular, are dominating other plants on the West coast, Colorado and the entire East and Midwest.

Natural historians determine the frequency of plants in a given area, Rocha said. They have determined that honeysuckles and rambler roses have become more and more frequent, while other native plants have disappeared.

Rocha’s job is to study the plants’ genes and determine the cause of this plant domination.

One theory is when the plants came to the United States, they had some genetic characteristic that allowed them to grow and spread faster than native plants.

“They started growing faster at full speed, out of control,” Rocha said.

This could be because the plants don’t have their natural enemies to control them.

The plants could have also cross-bred with relatives and formed new genes which allowed them to be more aggressive.

“All of the sudden, we put them all together and they started exchanging genes,” Rocha said.

The plants coexist peacefully with other plants in their own country, Rocha said, if they are planted with the plants they evolved with.

Rocha said he has seen examples of both cases, and right now he is in the process of determining which theory is the most important to the control of these species.

He uses molecular markers, which show the sequences of DNA for the plants. He is checking to see if the same DNA sequences from cultivated plants are in the foreign plants. This would prove they cross-bred and became more aggressive.

The only way to prevent the extinction of other plants is to stop planting the foreign species of honeysuckle and rambler roses in gardens, Rocha said. If people stop buying them, plant stores will stop selling them.

“If you have some of those plants in your garden, you should get rid of them,” he said. “These are species that are harmful to the environment in the long run. These plants are there because of our fault, and not because nature put them there.”

Rocha said people also should research whether a plant is invasive before they plant it.

In the long run, Rocha hopes his research will teach park managers to control these species populations.

Contact science reporter Allison Remcheck at [email protected].