Molecular phylogenetic studies of the genera of tribe Polygonateae (Asparagaceae: Nolinoideae): <i>Disporopsis</i>, <i>Heteropolygonatum</i>, and <i>Polygonatum</i>.

The Polygonateae (Asparagaceae) are a subtribe of the Nolinoideae that is redefined here to include three genera which are investigated here: Disporopsis; Heteropolygonatum, and Polygonatum. This group of genera, characterized by their axillary-flowered habit, are closely related but differ greatly in their morphology, cytology, and diversity. A molecular phylogeny is presented to show their relationships to one another and to closely related outgroups based on data from whole chloroplast genomes with low taxonomic sampling. The results show that the genera of the Polygonateae are each monophyletic, and also show that a fourth genus, Maianthemum, that was traditionally included in Polygonateae is not accurately placed there and should be excluded. A second set of analyses was based on an expanded dataset with high taxonomic sampling using a few selected loci from the chloroplast, mitochondrial, and nuclear genomes. The results confirmed the revised delimitation of Polygonateae that excludes Maianthemum and the respective monophyly of Disporopsis, Heteropolygonatum, and Polygonatum. Species-level relationships within each individual genus were analyzed, in part to allow assessment of the placement of many novel or obscure species that have been described (or resurrected) recently. Finally, the phylogenetic results from the expanded dataset were used to test various hypotheses regarding cytological evolution in the subtribe, and the results showed a pattern of descending (or in a few cases ascending) dysploidy that underlies the observed variation in chromosome numbers.