Relationships of the New Zealand mountain ribbonwoods (Hoheria glabrata and H. lyallii: Malvaceae), based on molecular and morphological data

Abstract

Cluster and principal coordinates analyses of leaf morphological data support the recognition of Hoheria glabrata and H. lyallii at species rank. H. glabrata is distinguished by long leaves with distinctly cordate bases, sparsely hairy surfaces, shallow marginal indentations, and an acuminate apex. This species occurs in western parts of the South Island and in Taranaki in the North Island. In contrast, the leaves of H. lyallii are shorter, have truncate bases, moderately to densely hairy surfaces, and an acute apex. H. lyallii has a more restricted distribution, mainly occurring in Canterbury and Marlborough with a disjunct population in Nelson. A new combination, H. ×allanii, is provided for the interspecific hybrid H. angustifolia × H. lyallii. Phylogenetic analyses of ITS and trnK/matK sequence data provided strong support for the recognition of the genus Hoheria, but supported conflicting species groups. The trnK/matK analysis recovered two main clades. One clade comprised all samples of H. glabrata and most samples of H. lyallii, and the other clade included three samples of H. lyallii and all of the other species of Hoheria (H. angustifolia, H. equitum, H. ovata, H. populnea, and H. sexstylosa). Two analyses of the ITS data were undertaken and these provided little indication of species relationships in Hoheria. However, an ITS analysis that excluded H. glabrata and H. lyallii samples with heterogenic nucleotide sites recovered a well‐supported clade that included all specimens of H. glabrata and a weakly supported clade that comprised most of the specimens of H. lyallii. The conflicting signal from the trnK/matK and ITS sequences provides evidence of hybridisation between different species of Hoheria. Four samples in the ITS data had heterogenic nucleotide positions and in the trnK/matK data three of the H. lyallii specimens had the chloroplast haplotype of another species of Hoheria.