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story.lead_photo.caption A new plant, a Eupatorium hybrid, has been found in south Arkansas, according to the Arkansas Natural Heritage Commission.

A new thoroughwort plant variety has been found in south Arkansas.

Actually, it’s a hybrid of a couple of other thorough-worts — Mohr’s and lance-leaf thoroughwort — but it has never been documented anywhere, according to the Arkansas Natural Heritage Commission.

Theo Witsell, a botanist and ecologist with the commission, said researchers don’t know yet whether the new hybrid will be able to reproduce asexually from seed, making genetic copies of itself. They hope to figure that out within the next year.

“Sometimes you just get a hybrid that comes up, lives for a couple of years and doesn’t survive,” said Edward Schilling, professor of plant systematics at the University of Tennessee in Knoxville. “Plants hybridize quite a bit. The challenge will be to say, ‘OK what’s this new hybrid doing?’”

Thoroughworts are in the genus Eupatorium, a large group of plants in the sunflower family. They got their common name because the leaf stems of one species appear to pierce, or go through, the leaves.

Some thoroughworts are also known as bonesets. The plants were used in folk medicine to treat dengue fever, also known as break-bone fever, Witsell said.

The ability of thorough-worts to reproduce asexually from seed occasionally allows what would normally be a one-time sterile hybrid between two different species to become self-sustaining and capable of reproducing from seed to create entire populations, according to a post at

This asexual reproduction is known as apomixis.

“It’s kind of a scientific curiosity,” Shilling said. “If we could harness it, you can visualize producing something like hybrid corn that could basically reproduce copies of itself.”

Witsell and Jim Keesling, a field volunteer, sent leaf tissue from some of the unusual looking plants they collected to Shilling. His team analyzed the plant DNA and confirmed that one was a new hybrid and three others were species that hadn’t been previously documented in Arkansas, according to the online article.

Two specimens Keesling collected in Calhoun and Ouachita counties were confirmed to be Mohr’s thoroughwort, which was previously known to grow only in southern Louisiana, adjacent Texas and states east of the Mississippi River.

Shilling said this plant is common in the Gulf Coastal Plain, but Arkansas is north of its usual range.

“Has it always been out there, and we haven’t looked in the right place, or is it moving northward as climate changes?” he asked.

Two other samples Keesling collected in Calhoun County were found to be the hybrid thoroughwort.

Schilling also examined two samples that Witsell collected a few years ago, and both were new species to Arkansas. A plant Witsell found in Van Buren County in 2010 was determined to be Torrey’s thoroughwort, and one from Greene County in 2011 was Vasey’s boneset, according to the online article.

Witsell suspects that most of these plant species were in Arkansas all along.

“We don’t think they just showed up,” he said. “We’re discovering things all the time. It’s a common misperception that we know everything about plants. We’re finding new things all the time.”

Traditionally, Arkansas botanists have recognized 10 Eupatorium species and two hybrids as being in the state. Earlier work by Schilling added two more species to this list from the Gulf Coastal Plain of south Arkansas.

This last round of DNA work has added three more species and another hybrid to the tally of Arkansas flora kept by the Natural Heritage Commission, bringing the totals to 15 species and three hybrids.

Witsell said he has more samples to send Schilling, and he suspects some of them will be new to Arkansas.

Photo by SOURCE: Biota of North America Program / Arkansas Democrat-Gazette
A map showing the Known range of Mohr’s thoroughwort

Print Headline: Researchers discover new plant hybrid in state

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