Assessing wind and mammals as seed dispersal vectors for Lespedeza cuneata
Lespedeza cuneata (Fabaceae) is an erect semi-woody forb which can reach 2 m in height. Native to Asia and Australia, L. cuneata was first introduced into the US in 1896 where it invades grasslands and open forest communities often forming dense monocultures which compete with native species for light and nutrients. Although the species is a prolific seed producer, information on seed dispersal is limited and primary based on anecdotal reports. Small numbers of seeds have been found in the faeces of birds, cattle and deer indicating that endozoochory is possible. Seeds lack any significant morphological characteristics such as wings which would aid wind dispersal or burrs which would aid dispersal by attaching to the fur or wool of mammals. In the current study, using a series of field and laboratory experiments, wind and mammal fur were tested as mediators of seed dispersal. For wind, seed traps were arranged radially from 0.5 m to 3 m from the edge of a population of L. cuneata and were left for one month. The results showed that wind direction strongly influenced dispersal distance. For movement by animals, seed retention was tested by fitting pelts of deer, coyote and raccoon to artificial torsos and moving these torsos on a one-wheeled carrier through the natural habitat. Seeds were shown to be readily dispersed by mammal fur where the number of seeds retained was higher for animal species with longer fur (racoons). Currently L. cuneata is absent from the natural environments within the EPPO region but the impacts of the species in other regions of the world, and the fact that the species is available through horticulture within the EPPO region, warrant an evaluation of the risks it may pose to the region. L. cuneata is due to be risk assessed as part of the LIFE project ‘Mitigating the threat of invasive alien plants in the EU through pest risk analysis to support the EU Regulation 1143/2014’.
Sources
Quick, ZI, Houseman GR, Bűyűktahtakin IE (2016) Assessing wind and mammals as seed dispersal vectors in an invasive legume. Weed Research 57, 35-43.