Geographic and Ontogenetic Variation in Morphology of Australian Waratahs (Telopea: Proteaceae)

Abstract

In this empirical study of species boundaries in a small genus of plants, we take the view that species are ambivalent; some appear to be monophyletic taxa, but some lack autapomorphies and are metataxa. As an operational definition, we recognized species from differentiated clusters in phenetic space whose distinctness was assumed to be the manifestation of underlying, fixed, and qualitative differences following speciation. These units were considered appropriate as terminals for phylogenetic reconstruction. The appropriateness of different phenetic methods in relation to models of infraspecific geographic variation and evolution is discussed. At the population level, ordination was more suitable than either cladistics or cluster analysis because it does not impose a rigidly hierarchical pattern on the data when none is expected. Variation among populations of Telopea was investigated by phenetic analysis of adult morphology. The main questions were whether the conventional distinction of T. mongaensis Cheel from T. oreades F. Muell. could be justified and whether disjunct populations referred to T. speciosissima (Smith) R.Br. in the Gibraltar Range, northern New South Wales, constituted a distinguishable taxon. The Gibraltar Range waratahs were distinguishable from typical T. speciosissima by their abundant ferruginous hairs, elliptic to obovate leaves, and numerous teeth along the lower half of the leaf margin; we propose recognizing them as a new species. Ordination analysis revealed a strong ontogenetic pattern within populations of T. speciosissima sensu lato, indicating that adult plants were retaining lobed intermediate leaves. Canonical variate analysis confirmed that this pattern was distinguishable from the between-population geographic pattern, but cluster analysis confounded the geographic and ontogenetic patterns. Conventional recognition of T. oreades and T. mongaensis as distinct species was supported by both ordination and cluster analysis. One population was mixed, with little evidence of hybridization between the sympatric species. Canonical variate analysis of populations was confounded by the heterogeneous population.