The importance of genetic variation for the viability of small avian populations:The Seychelles Warbler and the African Marsh Warbler

Nowadays, many natural populations have to face up to problems such as genetic drift and 'forced' inbreeding as a result of reduced numbers and population isolation. This is thought to have a major effect on their survival. Research on the isolated Seychelles warbler showed that fitness parameters an not negatively affected by a high inbreeding Frequency and a low level of heterozygosity. However, one has to be careful to translate these results to other isolated species. It is hypothesised that the effect of 'genetic erosion' on fitness may be less disastrous for island species, which are used to go through narrow population bottlenecks. as compared to continental species. Conservationists should be aware of these differences between species and of the fact that the long-term prospects can be reduced by lack of adaptive genetic potential.