Invasion Dynamics of Plants in the British Isles

Invasive plants are one of the biggest threats to biodiversity worldwide. Modelling populations and geographic ranges is a prioirity for conservation and species management. The two most common models used for this are the Reaction-Diffusion model and the Integrodifference equation models, both of which have limitations. A model proposed by Franco et al. (unpublished) for the investigation of binomial biological processes was used to examine geographic spread of 39 species of invasive plants of the British Isles. The raw data for this study was taken from the Botanical Society of the British Isles; Vascular Plants Database which records plants in hectads (10x10km grids). The model has a cumulative distribution function (cdf) equation which smoothes recorded geographic range records over time. It also has probability density function (pdf) equation which can depict rate of invasion over time. Ten year intervals were used in this investigation to eliminate the irregularity of records. There are four parameters to the model; S, total number of hectads invaded, g species invasive potential, b ecosystem potential for invasion and t0 time lag for invasion. b and t0 were calculated using non-linear regression. The model produced good cdf and pdf graphs for comparison and further analysis allowed for interrogation of these parameters. None of the parameters were significant in themselves to effect plant invasion but t0 and b were slightly correlated suggesting that time lag of invasion and habitat invasibility were important. Both were not correlated to the total number of hectads invaded, S.Faculty of Science and Technolog