GENE FLOW BY POLLEN - IMPLICATIONS FOR PLANT CONSERVATION GENETICS

The absence of gene flow, genetic isolation, is frequently emphasized in conservation genetics. However, the presence of gene flow can play an equally important role in determining the genetic fate of populatio ns. Here, I first review what is known of patterns of gene flow by pol len. Gene flow by pollen is often substantial among plant populations. I next review the expectations for gene flow patterns in the small po pulations typical of endangered species. Then, I consider what role ge ne flow can play in plant conservation genetics. Depending on the spec ific situation, such gene flow could be either beneficial or detriment al. Geographically disjunct populations might not always be as reprodu ctively isolated as previously thought, and thereby less vulnerable to detrimental drift-based processes. On the other hand, conspecific or heterospecific hybridization may lead to extinction by outbreeding dep ression or genetic assimilation. Also, the field release of transgenic plants may lead to the escape of engineered genes by crop-wild plant hybridization. Such "genetic pollution" could have profound effects on the fitness of wild species with the potential for disrupting natural communities. Gene flow can be an important force in plant conservatio n genetics, and its potential role should be considered in any plant c onservation management program.