Jennifer Forman of Dr. Richard Kesseli’s lab defended her dissertation, “Of Knotweed and Other Weeds: Invasive Plants at Home and Abroad.” Currently the work is being prepared for publication in scientific journals.
Jenn came to us from Boston University, where she received a MS in Environmental Studies. Around the biology department she became known as a computer guru during her time as the computer assistant. This basically meant that people relied on her constantly to fix their computer problems, preventing her from completing any actual dissertation work.
After retiring from the computer gig in the department, she was able to collect a vast amount of information regarding invasive plant species. Plants that are introduced into non-native environments can be separated into four categories: Benign, Casual/Escape, Naturalized, and Invasive/Weedy. Benign plants cannot grow on their own and require human assistance either within a botanical garden or a household. Casual/Escape plants can support themselves independently and can be found near their introduction site. Naturalized plants have become incorporated into the wild of their non-native environment. Finally, Invasive/Weedy plants spread throughout their non-native environment aggressively.
The United States spends $25 billion dollars annually combating Naturalized or Invasive plant species. Invasive plants displace native flora and disrupt ecosystems. At least 23,000 plants species have been intentionally introduced within North America, 6,000 of which have become naturalized or invasive. In fact, 7% of U.S. flora are invasive species.
One question that Jenn addressed is why are European plants invasive to the US, but not so much the other way around. A few hypotheses are 1) Old World plants are better competitors and act as better weeds; 2) Old World plants are “used to” or have adapted to grazing animals, whereas New world plants have not; and 3) Immigration rates are greater from the Old World to the New World.
Jenn collected the life history, native country, and the number of introductions of 6,000 plants species from the U.S. to Europe from 100 sources. She found that 85% of these 6,000 plants introduced are benign, and only 1% are weedy. In addition, half of the plant species introduced into Europe are from the U.S.
From all of this data, Jenn was able to statistically test a few hypotheses. She demonstrated that plants from specific families of taxonomy are weedier than others. Also, the higher the number of times a plant is introduced into its non-native environment, the more likely it is to be non-benign. Less than 20% of plants that were introduced once are non-benign, whereas 80% of plants that were introduced 3 or more times and 100% of plants that were introduced 5 or more times are non-benign.
She was also able to show that ‘weediness’ in America is a decent predictor for ‘weediness’ in Europe. In fact, a warning list of 222 plant species that are weedy in America, but not yet weedy in Europe will be published as an appendix in an article that should be published later this year.
The other half of her dissertation elucidated the breeding system of the Japanese Knotweed, an extremely weedy plant with an underground stem base. Her work included Greenhouse work to determine seed viability. Also, molecular work with DNA determined the number of chromosomes present in the species. This work has recently been accepted for publication and should be published in the apring. More information on Japanese Knotweed can be received from her website: http://fisher.bio.umb.edu/Knotweed.
Jenn also maintains a web site, “Jenn’s Web Garden,” which includes links to information about invasive plant species, information about the genus of the month, and articles and talks of her work. Her articles are from the online journal of the Massachusetts chapter of The Society for Conservation Biology, Friends of the Blue Hills, and Conservation New England. She also gave a talk, “Through the Looking Glass: History and Consequences of the Introduction of American Plant Species into Europe” to the New England Botanical Club. http://fisher.bio.umb.edu/pages/jennifer.htm.