Figure 1.

Decline in the relative frequency of the native genotype in a neutrally selective environment (i.e. all genotypes are equally fit). The default parameter values (dashed line) for vegetative growth rate and fecundity are, respectively, R=1.05 and S=0.1. The initial population consists of 99% native and 1% exotic genotypes, and all genotypes are assumed equally compatible. The following deviations from the standard are considered: reduced seedling production (bold line, S=0.01), reduced compatibility (pluses, $\alpha (y,z)=1-0.5|y-z|$ for $|y-z|<2$; 0 otherwise) and reduced initial frequency of the native (circles, 90% native and 10% exotic).