The relationship between community diversity and exotic plants: cause or consequence of invasion? - Invasive Plants: Ecological and Agricultural Aspects - page 88

Figure 4. General association between invader cover and species richness for Lonicera japonica and
Rosa multiflora . Regression analysis: Lonicera - F 1,478 = 40.84; P = 0.0001; R 2 = 0.08; Rosa -
F 1,478 = 16.86; P = 0.0001; R 2 = 0.03.
selective invasion of high richness plots by these two species would tend to
generate a positive association between invasion and diversity. Patterns of
diversity are transient within the BSS, suggesting that there are no inherent dif-
ferences between high and low richness plots that may influence invasibility.
Invasibility at the neighborhood scale appears to be influenced primarily by
stochastic events that generate opportunities for establishment [103], neigh-
borhood species richness, and positive and negative interactions with resident
species [55]. Once invasion had occurred, initial species richness did not influ-
ence the increase in cover of either species.
Finally, we determined the association between the increase in cover of the
invading species and the change in species richness for those plots that were
invaded during the observation periods. Change in cover for these two invaders
represents increased cover of established individuals and, to a lesser extent, the
recruitment of new individuals. This analysis assesses the ability of the invad-
ing plant to influence other species within the neighborhood [72]. As the cover
of both invaders increased, the change in total species richness of the plot
changed from a slight increase in richness over time to a net loss of species
(Fig. 6). This shows that species were disproportionately lost from plots that