The problems with hybrids: setting conservation guidelines

HYBRIDIZATION (see Glossary) provides an exceptionally tough set of problems for conservation biologists. The issues are complex and controversial, beginning with the seemingly simple task of defining hybridization1. Detection of hybridization can also be difficult, although it is becoming easier through the development of various molecular techniques over the last two decades. In spite of improved molecular data that can be collected with relative ease, interpreting the evolutionary significance of hybridization and determining the role of hybrid populations in developing conservation plans is more difficult than is usually appreciated. According to Stone2: ‘It is an understatement to say that hybridization is a complex business!’. The harmful effects of hybridization, with or without INTROGRESSION, have led to the extinction of many populations and species in many plant and animal taxa3. Hybridization is especially problematic for rare species that come into contact with other species that are more abundant. Rhymer and Simberloff3 have concluded that the severity of this problem has been underestimated by conservation biologists. The increasing pace of the three interacting human activities that contribute most to increased rates of hybridization (introductions of plants and animals, fragmentation, and habitat modification) suggests that this problem will become even more serious3. Hybridization has long been recognized as playing an important role in the evolution of plants4. However, recent studies have found that hybridization has also The problems with hybrids: setting conservation guidelines