Ecological species concepts are generally partial rather than all-encompassing, and tend to act as adjuncts to more universal conceptions. It is clear that all ecological concepts rely heavily on the pre-eminent role of natural selection to maintain isolation between groups. Selection also plays a critical role in the definition and delimitation of asexual species, to which, among others. The chapter argues that agamospecies and that the inferences made about quasispecies by Eigen be applied to agamospecies. It is an asymmetric version of the nothospecies concept. It also applies to some plant species. Phenetics developed from the work of Robert R. Sokal and Peter Henry Andrews Sneath, who trace their attempt to produce a "natural" taxonomy back to Adanson, who used a multivariate classification scheme in Familles des Plantes. A species nominalism must be directed to the category or rank of species, and must claim that there is no sense in which that categorical term has any application.