Phylogenetic Relationships of Burmeistera (Campanulaceae: Lobelioideae): Combining Whole Plastome with Targeted Loci Data in a Recent Radiation

The field of molecular systematics has benefited greatly with the advent of high-throughput sequencing (HTS), making large genomic datasets commonplace. However, a large number of targeted Sanger sequences produced by many studies over the last two decades are publicly available and should not be overlooked. In this study, we elucidate the phylogenetic relationships of the plant genus  Burmeistera  (Campanulaceae: Lobelioideae), while investigating how to best combine targeted Sanger loci with HTS data. We sequence, annotate, and analyze complete to nearly complete plastomes for a subset of the genus. We then combine these data with a much larger taxonomic dataset for which only Sanger sequences are available, making this the most comprehensively sampled study in the genus to date. We show that using a phylogeny inferred from the species with plastome data as a topological constraint for the larger dataset increases the resolution of our data and produces a more robust evolutionary hypothesis for the group. We then use the resulting phylogeny to study the evolution of morphological traits thought to be important in  Burmeistera , and assess their usefulness in the current taxonomic classification of the genus. The main morphological character used to delimit subgeneric sections, the presence or absence of hairs on the apex of the two ventral anthers, shows a complex evolutionary history with many changes in the tree, suggesting that this character should not be used for taxonomic classification. Although it is too soon to propose a new subgeneric classification for  Burmeistera , our results highlight some morphological traits shared by whole clades that could potentially be used in future taxonomic work.