Comparative morphology and phylogeny of Nicotiana section Suaveolentes (Solanaceae) in Australia and the South Pacific

The evolutionary relationships within the Nicotiana section Suaveolentes, primarily composed of Australian endemics, have been clarified through a combined morphological and molecular analysis. The study revealed that N. fragrans (New Caledonia and Tongatapu) and N. fatuhivensis (Marquesas islands) form a basal lineage in the Australian and South Pacific clade, while N. forsteri (eastern mainland Australia, Lord Howe Island, and New Caledonia) is the sister taxon to all other Australian species within this section. A phylogenetic sequence was identified, reflecting a reduction in chromosome number, with early lineages exhibiting counts of n = 24 or 23. Two distinct clades emerged: the 'N. simulans clade' (n = 20) and the 'N. suaveolens clade' (n = 19, 18, 16, or 15). The research integrated discrete morphological characters of seeds and trichomes, along with gap-coded quantitative measurements of flowers and vegetative organs, analyzed using maximum parsimony and splits network methods. These findings were compared to and combined with previously published molecular datasets, providing a comprehensive understanding of the group's evolutionary history.

Marks, C. E., Newbigin, E., & Ladiges, P. Y. (2011). Comparative morphology and phylogeny of Nicotiana section Suaveolentes (Solanaceae) in Australia and the South Pacific. Australian Systematic Botany, 24(2), 61–86. https://doi.org/10.1071/sb11006