Colonization, extinction and species numbers of vascular plants for the island Gran Roque, Venezuela

Records of vascular flora from three expeditions encompassing 107 years are compared for the island Gran Roque, located in the southern Caribbean. The number of vascular plant species increased from twently-five species in 1871 to thirty-three in 1950 and to forty-nine in 1978. Successfull immigrants were primarily herbs. Colonization for the earlier period occurred at a slower rate than the latter period, 0.177 spp./yr versus 0.643 spp./yr, respectively. Early period colonists were a mix of strand species and cosmopolitan weeds, whereas colonists of the latter period were predominantly cosmopolitan weeds and a few woody escapes. Only two of the island habitats, comprising less than 7.0% of the island area, were exploited by colonists. Extinctions were few, occurred primarily among woody aboriginal species, and were mostly restricted to a single habitat. The rate of extinction did not increase with the increased number of island species. Changes in the nature of colonist species correlate with a shift from an island used as the base for a fishing community to one increasingly exposed to tourism from the continent.