Introduced species in nature reserves in Mediterranean-type climatic regions of the world

Abstract

The invasions of introduced species into three nature reserves in California, two in Australia, one in Chile and one in South Africa are described. In most reserves the major invasion has been by herbs, primarily annual grasses from Europe and the Mediterranean Basin. It appears likely that fire regimes have been altered and the density of some native plant populations reduced. In the South African reserve, invasions by introduced trees threaten certain native plant species with extinction. Over all regions smaller reserves tend to show higher proportions of invasive introduced species in their vascular plant floras, and both freshwater fish and mammalian faunas, than do larger reserves. Few vertebrates are though to pose significant conservation problems. These reserves tend to be susceptible to invasion of non-native species from elsewhere on their own continents. The intentional or accidental introduction of species to these reserves should be avoided.