Variation in the Dendrobium speciosum (Orchidaceae) complex: a numerical approach to the species problem

Abstract

The Dendrobium speciosum Sm. (Dendrobium sect. Dendrocoryne: Orchidaceae) complex is a taxonomic problem because of intrapopulational and interpopulational heterogeneity. The pattern of morphological variation exhibited is partly associated with geographical regions in eastern Australia, from the base of Cape York Peninsula to eastern Victoria. Variation within the species was investigated by multivariate and univariate analyses of data obtained from living specimens. The analyses that differentiate section Dendrocoryne species do not form discrete groups for previously recognised regional or any other variants of Dendrobium speciosum, providing no support for recognising subgroups of Dendrobium speciosum at species level. Dendrobium speciosum is regarded as a variable species forming a complex continuum. In some designated areas, the varieties speciosum, hillii, grandiflorum, curvicaule, pedunculatum and capricornicum can be retained. It is strongly recommended that all individuals be specified by their geographical origin since this is the only system that provides unambiguous identification.