Vascular flora of 71 artificial islands of varying agewas analyzed in 22 fishponds, Třeboň Basin, the Czech Republic. Data on species richness were interpreted in terms of Wilson’s (1969) hypothesis on the development of biotic communities. An increase in species richness during the non-interactive stage (one to two years) and a decrease in the interactive stage (three to six years) were both statistically significant. As predicted, by Wilson’s hypothesis, there was also an increase in species richness in the assortative stage (seven to >50 years), however, this trend was not significant. This successional pattern was confirmed by the vegetation development recorded on 34 re-sampled islands. For these islands the positive change in species richness during the assortative stage was significant based on both paired t- and binomial tests. Contributions of island area, elevation, and isolation during individual successional stages were evaluated. As a whole, this is probably the first clear confirmation of Wilson’s hypothesis for vascular plant communities on islands.