The taxonomy and evolution of weeds

The evolutionary responses of weeds to changing conditions suggest that although selection within populations is important, changes in the species composition of a weed flora may be a more common response to selection.

Abstract

Summary: Taxonomy describes and classifies (i.e. maps) the diversity of nature. The most useful classifications are those that permit the delimitation, and subsequent identification, of species in such a way that they exhibit genetic differences and ecological preferences. However, all classifications have limitations for weed scientists. Genetic variation within species may be just as important as differences between species to the development of weed control practices. Because traditional concepts, such as species, variety and ecotype, cannot fully reflect the products of evolutionary processes, alternative taxonomic or para‐taxonomic representations of variation are considered. The dependence of plant nomenclature on these inherently limited taxonomic concepts is also discussed, and ways are suggested of minimizing the resultant degree of instability in the scientific names of weeds. The evolutionary responses of weeds to changing conditions suggest that although selection within populations is important, changes in the species composition of a weed flora may be a more common response to selection. Recombination through hybridization can be particularly significant, especially in the evolution of weeds which are genetically close to the crop species.