Taxonomy of agamic complexes in plants: A role for metapopulation thinking

Abstract

The argument is made that species should be comparable with respect to the numbers of genotypes they include, regardless of whether their reproduction is exclusively sexual or not. Specifically, this means recognizing species at a level comparable to that of the section or series, as these are used in genera likeCrataegus L. orTaraxacumWeber ex F.H.Wigg. Anticipated advantages of this approach for the taxonomy of agamic complexes include the following: (1) a common basis for communication between taxonomists and population biologists, hence (2) the opportunity to find possible explanations for patterns of variation in theoretical models of population behavior. In addition, (3) revising the hierarchical level at which species are recognized will make it easier to avoid describing species that are paraphyletic, i.e. that include some but not all related genotypes sharing a common ancestor. As an example, revising the hierarchical level at which species are recognized makes it possible to see many agamic complexes as being made up of metapopulations of genotypes that arise and go extinct as habitats become available and then disappear for whatever reason (succession, disturbance, etc.) and at whatever scale (local, regional, continental).