Phylogeny of the SE Australian clade of Hibbertia subg. Hemistemma (Dilleniaceae).

Abstract

Hibbertia Andrews (Dilleniaceae) has been studied for 200 years, but the systematics of species from SE Australia have not been addressed. Many of the taxa placed into 16 informal groups by Toelken are undescribed and their phylogenetic relationships are unknown. Therefore, a comprehensive morphological and molecular phylogenetic analysis of 87 SE Australian taxa within Hibbertia subg. Hemistemma was conducted. Morphological studies were carried out including vegetative, indumentum, floral and leaf cuticular characters to assess intra-specific variation, determine any major lineages and taxon boundaries as well as to explore character evolution. Nuclear rDNA (ITS) and intergenic spacer regions of cpDNA (trnL-F) were amplified and the results compared and combined with morphological phylogenetic analysis. The results, all the 16 informal species groups proposed by Toelken were placed instead into eight clades, with strong support for different species pairs and sister relationships. Most infrataxa within more variable species were not part of monophyletic lineages and none of the 16 informal species groups of Toelken were supported. Vegetative, floral and leaf cuticular characters were important in understanding species of Hibbertia phylogenetic relationships, with general variation in numerous morphological characters such as hair type and density, androecium and gynoecium characteristics, stomata (shape and size), anticlinal and periclinal cell walls and trichome bases. The molecular data and combined data analysis enabled us to recognise eight clade, most with low support, with different groups of closely related taxa received strong support. Several infrataxa within more variable species did not form monophyletic lineages. Despite a high number of homoplasious, several morphological synapomorphies for Clade/taxon definition were discernible such as: lack of indumentum on stem, revolute leaf margins, acuminate inner sepal bases, >15 mm leaf blade width, 10.1–15 mm leaf blade width, absent of inner sepal, ≥10.1 mm inner sepal width, terminal pores anther dehiscence, ovate petal shape, spherical seed shape and 3.1–4 abaxial epidermal cell length to width ratio.