Title: Creating a robust weed: Hybrid offshoots are more difficult to control
[Newswise 6 Oct. 2010] — Invasive Plant Science and Management – The
only thing worse than an invasive weed that’s hard to get rid of is a hybrid of
that weed that’s nearly impossible to eradicate. When two plant species
contribute to a hybrid, new capabilities for invasion can also be created.
Recently formed plant hybrids have been shown to spread rapidly.
A study reported in the current issue
of the journal Invasive Plant Science and Management examined the hybridization
and spread of Japanese knotweed and giant knotweed in the United States.
Previous studies have focused on this occurrence in the plants’ native Asia and
in Europe, but not in North America.
Using flow cytometry, researchers investigated DNA content of established
plant families in a common garden, seedlings grown from common garden parents,
and wild populations. The authors report that not only did the two varieties of
knotweed cross-breed in a controlled garden setting, but the hybrids were
identified in field populations in Massachusetts as well. Nearly all the created
hybrids showed strong growth, seed set, and the production of viable pollen.
Significant introgression, where a hybrid crosses once again with one of its
parents, is also suggested by the study results. As introgression progresses, a
more diverse swarm of invasive plants is created. Once populations are
established, options for eradication become more limited.
The authors emphasize the importance of managing sexual reproduction of
invasive species. Careful management of giant knotweed is essential to limiting
its role as a parent to a hybrid. Hybrids also should be recognized as invasive
species that are diverse, vigorous, and fertile.