Phylogenetics, Taxonomy, and Chromosome Number Analysis of <i>Sanvitalia</i> (Asteraceae-Heliantheae-Zinniinae)

Abstract— Sanvitalia (Asteraceae), a New World endemic, is poorly understood from a phylogenetic perspective. While chromosome number variation is well documented for the genus, previous studies lack a phylogenetic context for chromosome number evolution, with one species, S. fruticosa , lacking a published chromosome count. We collected molecular sequence data from the nuclear ribosomal ITS region and three plastid loci from multiple individuals of each species of Sanvitalia and additional members of the Zinniinae to create phylogenetic trees and study the evolutionary history of the clade. A complete taxonomic treatment was produced as well as a dichotomous key to species. The first chromosome count for S. fruticosa was rendered (2 n = 16) and a chromosome number analysis was completed using maximum likelihood methods that account for different modes of chromosome number change. Support for two separate whole genome duplication events in the genus is presented here. This study resulted in deeper understanding of the relationships within Sanvitalia and closely related genera, chromosome number evolution and genome duplication in Zinniinae, and the closest relative ( S. ocymoides ) of the enigmatic and amphiequatorial disjunct S. versicolor . We also provide support for the prior transfer of S. tenuis to Zinnia , and two new sections within Sanvitalia .