Molecular Phylogenetics of Core Brassicales, Placement of Orphan Genera Emblingia, Forchhammeria, Tirania, and Character Evolution

Many genera previously placed in the traditionally circumscribed Capparaceae are either unrelated or, more commonly, isolated lineages in the order Brassicales. This study examines the relationships of three of these orphan genera, Emblingia, Forchhammeria, and Tirania, in the context of a focused analysis of the core Brassicales. In order to assess relationships of these genera, analyses were conducted across Brassicales using chloroplast rbcL, ndhF, and matK sequence information. Both maximum parsimony and maximum likelihood analyses place all three genera in the well-supported core Brassicales (Brassicaceae, Capparaceae, Cleomaceae, Gyrostemonaceae, Pentadiplandraceae, Resedaceae, and Tovariaceae). The Asiatic Tirania and New World tropical Forchhammeria are closely related to two small families, the pan-temperate Resedaceae and the Australian Gyrostemonaceae. These analyses also indicate a novel placement of Emblingia as sister to all remaining members of core Brassicales. Although there is strong support for the relationships among most of these taxa, relationships of Pentadiplandraceae and Tovariaceae are weakly resolved. Thus, the core Brassicales is a biogeographically dispersed lineage that is comprised of many small and morphologically distinct clades plus the large crown group Brassicaceae s. lat. Patterns of morphological evolution appear complex, especially in floral merosity and carpel and locule number. Likewise, the evolution of breeding systems within this lineage involves recurrent shifts towards monoecy or dioecy, and possible reversals to bisexuality. Further sampling of Capparaceae tribe Stixeae is critical for any taxonomic recommendation of familial status for these orphan genera.