Sunday, February 22, 2009

The incredible spreadable weeds

ResearchBlogging.orgResearch into the spread of non-native species usually assumes a long time lag between introduction and rapid spread, and many studies cite 50 years as the lag time. The reason for believing this is that it is thought that there needs to be sufficient time for adaptations to fine tune the fit between the exotic and its new environment, or that densities are so low to start with, finding mates and buffering populations from stochasticity (i.e., Allee effects) takes time. However, Curtis Daehler at the University of Hawaii, collected information on purposeful plant introductions into Hawaii in the 1920s. 23 of those planted have become serious invaders and the herbacious species showed a lag time of 5 years and 14 years for woody species. Knowing that lag times can be much shorter then we previously thought means that monitoring and management activities need to much more aggressive. It seems we can no longer assume a period of relative safety after a new species in introduced, new records of non-natives needs to be followed active assessment and perhaps intervention.

Curtis C. Daehler (2009). Short Lag Times for Invasive Tropical Plants: Evidence from Experimental Plantings in Hawai'i PLoS ONE, 4 (2) DOI: 10.1371/Journal.pone.0004462

1 comment:

Anonymous said...

We got a bunch of weeds spreading across northern Australia, that are starting to cause havoc. There seems little political and community will to do anything about all but the most serious outbreaks (that threaten water supplies, etc).

The irony is that most of them were deliberately introduced and strongly promoted as cattle feed, and are still being promoted by the local agriculture departments and cattle farmers. While at the same time the environment departments are advertising about their serious weed potential and asking people to pull them out before they seed.

My favourite one to hate is Calopo (Calopogonium mucunoides, I think). Just about the perfect invader. Grows like wildfire, spreads and puts down roots every few inches, climbs and smothers all but the biggest plants, is nitrogenous, and produces hundreds of little hard tough seeds that are viable for up to at least 12 years in the soil.

And there are several other species that are serious problems.

Oh brother. What a farce.