Application of the phylogenetic species concept: A botanical monographic perspective

Abstract

Snow, N. (1997). Application of the phylogenetic species concept: A botanical monographic perspective.Austrobaileya 5(1): 1-8.The diagnosis of phylogenetic species and infraspecific taxa is considered from the perspective of botanical monography.Diagnosing phylogenetic species using population aggregation analysis (PAA) cannot be done in the herbarium, as it is a population-based procedure.However, herbarium specimens can be aggregated into phylogenetic species based on the presence of fixed characters, and PAA methodology in the field is encouraged to the maximum extent possible.The importance of diagnosing phylogenetic species by ordinary morphological means is stressed.A species is thus an aggregation of sexual or asexual semaphoronts consistently diagnosable by a fixed character or combination of characters recognizable by ordinary morphological means.Application of this species definition will generally decrease species numbers in botanical monographs and could therefore overlook significant but non-fixed phenetic variation.Given the widespread existence of such variation it is concluded that the recognition of infraspecific taxa remains desirable.However, since varieties are explicitly subordinate to subspecies in the Code and imply hierarchical pattern where none is expected to exist, the recognition of only one infraspecific category is recommended.