Introgression as a Spatial Phenomenon

Abstract

Abstract Biologists are devoting increasing attention to introgression, which is relevant to several topics of current concern. Since it is inherently a spatial phenomenon, introgression should be especially interesting to geographers. Hybridization, followed by introgression, occurs where two species (or ecotypes) meet, often after migration of one or both brings the two into proximity. If new genotypes created by hybridization and introgression are successful, they are likely to migrate further, while also increasing in frequency. Consequently, spatiotemporal analysis is usually necessary to properly interpret possible cases of introgression. Hypotheses are best formulated and tested by modifying the standard spatial introgression models to allow for hybrid fitness, temporal change, and real world habitat mosaics. In contrast, analyses that presume equilibrium population genetics, or that treat each taxonomic species as reproductively inviolate, inevitably lead to mistaken conclusions. A model is outlined showing how hybridization between a crop and wild relative may increase invasiveness, particularly in productive habitats. Keywords: biogeographyhybridizationintrogressionbiological invasionhybrid zone