EVOLUTIONARY POTENTIAL IN ORCHIDS: PATTERNS AND STRATEGIES FOR CONSERVATION

Abstract

Strategies for species conservation should be based on at least two perspectives. First, one should know the demographic health of component populations which includes their growth, decline and interdependence. The second perspective, which I address here, is the maintenance of evolutionary potential, i.e., the ability to respond to change. This potential depends not only on patterns of variation but also on how populations differentiate. One model of evolutionary potential and differentiation in orchids is based on small population dynamics and repeated founder events. Species that show high levels of genetic variation within populations but little among them represent the pool of possibilities for future founding events which generate small populations. When variation is highest among populations, the potential for speciation is very high because populations are already differentiated to some degree, gene flow is minimal, and episodes of genetic drift and natural selection may be common. Conservation strategies can be very different for the two extreme patterns. For high variation within populations and little among them, the focus should be on conserving many individuals and this could be accomplished at one or few populations without substantial loss of genetic resources. When variation is greatest among populations then one must conserve as many viable populations as possible. Patterns of genetic variation can be revealed by molecular methods as well as standard morphometric techniques. Thus, the tools for estimating genetic resources are available to all and interpretation of the results are possible within existing theoretical frameworks.