Natural hybridization and conservation

This review deals with natural hybridization, an important subject in conservation biology. Natural hybridization is defined as the secondary contact between two populations that have evolved separately over a long period of time. This process is uncommon in terms of the total number of individuals involved, but is much less unusual if we consider the number of species that hybridize. Thus, natural hybridization may be an important process in the shaping of the evolutionary trajectories of many plant and animal species. The possible consequences of natural hybridization, which can either promote or prevent evolutionary divergence between taxa and will involve many ecological factors, are analysed here. I question whether natural hybridization poses always a problem in conservation and try to answer when conservation biologists and managers do have a responsibility to take decisions. Several examples of hybridization related to management strategies are also discussed. In conclusion, I believe that it is impossible to provide conservation managers with a simple handbook explaining how to proceed in cases of hybridization--each case is unique and should be analyzed individually. The only advice is that the more we know about hybridization and the factors involved, the better we will be able to assess each situation, to establish the possible consequences and even to estimate the probability of success of any particular conservation strategy.