Evolutionary Ecology of Japanese Knotweed
Research goals: we plan to study japanese knotweed from two
Perspectives: 1) map the current locations in Broome Co. with
respect to road and river networks. If it doesn’t make seed, it
should not be able to disperse upstream, and therefore some
areas that would otherwise be vulnerable may currently be
safe – so long as care is taken to prevent dispersal via the road
network.
2) Evolutionary studies to determine genetic diversity present, whether
hybridization is occurring, and to what extent seed production may be
occurring (visual evidence suggests that a very small number of individuals
are now producing seed).
Introduction
Japanese knotweed (Polygonum cuspidatum) may be the worst invasive
plant species in the northeastern US, though because it is relatively recent
it is less well-recognized than some alien species that have been here
longer, such as purple loosestrife and giant reed. Japanese knotweed can
dominate floodplains, to the near exclusion of other plants. Currently, it
almost never produces seeds, dispersing instead by root pieces that are
moved by bulldozers or floods. In Europe, where it also is a serious
invading species, it hybridizes with Siberian knotweed, producing fertile
offspring that can produce seeds. Siberian knotweed also is now reported
in upstate NY, and it is to be expected that fertile hybrids will begin to
appear in our county. Successful seed production by this species (or
species complex) would greatly increase its invasiveness, turning into a
truly monstrous problem.
The Hybrid Soup Hypothesis
Spencer Barrett pointed out that alien species often have very low genetic
diversity, and therefore are poorly suited to the overseas environments
into which they have been introduced. He argued that those aliens that
are able to hybridize with closely related species pick up new diversity forming a hybrid soup - which can greatly increase their adaptation to
those new environments. This appears to be happening in Europe for
Japanese knotweed, and may be about to happen here.
Japanese knotweed (background) in Johnson City
The results should be of both theoretical interest – hybridization as an evolutionary
mechanism is a hot topic at the moment – and of practical benefit in guiding mitigation
efforts for dealing with this most problematic of invading , alien species.