A review of Dendrobium kingianum Bidwill ex Lindl. (Orchidaceae) with morphological and molecular-phylogenetic analyses

Abstract

Populations of Dendrobium kingianum Bidwill ex Lindl. from near Newcastle, New South Wales to southern and central west Queensland and encompassing all regions of the distribution were studied using field observations, morphometric analysis and nrITS sequences. A total of 281 individuals were used to construct regional descriptions of D. kingianum and 139 individuals were measured for 19 morphological characters, and similarities and differences among specimens summarised using multivariate statistical methods. Patterns of morphological variation within D. kingianum are consistent with a single variable species that expresses clinal variation, with short growing plants in the south and taller plants in the northern part of the distribution. The nrITS gene tree suggests two subgroups within D. kingianum subsp. kingianum, one comprising northern, the other southern individuals, which may overlap in the vicinity of Dorrigo, New South Wales. The disjunct D. kingianum subsp. carnarvonense in central west Queensland, which can be distinguished by a predominately subterranean habit and a narrower labellum midlobe, was resolved sister to D. moorei, which renders D. kingianum paraphyletic in the nrITS gene tree, but this position was not supported. Regional descriptions documenting clinal variation are provided. All previously described varieties, including D. kingianum var. pulcherrimum Rupp, are colour and growth forms of D. kingianum subsp. kingianum.