Welcome to the wonderful world of weedy plants!
Weeds are superevolutionary products of human civilizations and activities - without humans there would be no weeds, just wild plants.

Monday, February 20, 2012

Going once, going twice, going invasive!

I just read an interesting article (see citation at bottom) that describes various ways that species become invasive, and if invasive is really a good word to use.   Often there is a lag time between the first introduction until a species becomes common, overwhelming, and invasive.  The author argues that this lag time often is not a result of a biological process, but simply a continuous time for more introductions of the species to the area and human-mediated dispersal. Here are some quotes, laying out this theory:
"A single initial introduction may act as exclusive founding population. In the British Isles, all populations of the highly invasive Japanese knotweed Fallopia japonica are supposed to descend from one single clone probably introduced in 1848."

"Most frequently, however, successful non-native species are introduced repeatedly and often discontinuously over long periods from one or more original ranges into a new one."

"The success of these species was, in terms of naturalisation, poor with 7.4% naturalised. In contrast, 41.2% of the deliberately introduced taxa achieved naturalisation." {this is from a 1912 study in France}
Note the comment at the end, that deliberately introduced and spread taxa are the ones that become invasive, much more so than the accidentals.  The article describes the situation in Germany, but I think you would have a similar case in the US.  Some of our worst weeds were deliberately spread by humans and promoted as solutions to problems (kudzu for soil erosion and multiflora roses for hedges, for example).  Very interesting read.

Article, source for quotes: Kowarik, Ingo. 2003. Human agency in biological invasions: secondary releases foster naturalisation and population expansion of alien plant species. Biological Invasions 5: 293–312, 2003.

Species: Kudzu, Pueraria lobata, Fabaceae.

1 comment:

SteveK said...

And Nutria were introduced to control Kudzu! There is a danger in every trans-location of any species: evolution happens. The plant or animal finds new ways to thrive. It may take a long time, or it may be nearly immediate. As a rabble-rouser/cheerleader/recruiting sergeant for weed control and exploitation, I'm not pleased by biological controls even while they are working.