title: Evolutionary relationships within the lamioid tribe Synandreae (Lamiaceae) based on multiple low-copy nuclear loci.
abstract: The subfamily Lamioideae (Lamiaceae) comprises ten tribes, of which only Stachydeae and Synandreae include New World members. Previous studies have investigated the phylogenetic relationships among the members of Synandreae based on plastid and nuclear ribosomal DNA loci. In an effort to re-examine the phylogenetic relationships within Synandreae, the current study incorporates data from four low-copy nuclear loci, PHOT1, PHOT2, COR, and PPR. Our results confirm previous studies based on chloroplast and nuclear ribosomal markers in supporting the monophyly of tribe Synandreae, as well as sister relationships between Brazoria and Warnockia, and between that pair of genera and a monophyletic Physostegia. However, we observe incongruence in the relationships of Macbridea and Synandra. The placement of Synandreae within Lamioideae is poorly resolved and incongruent among different analyses, and the sister group of Synandreae remains enigmatic. Comparison of the colonization and migration patterns corroborates a single colonization of the New World by Synandreae during the Late Miocene/Tortonian age. This is in contrast to the only other lamioid tribe that includes New World members, Stachydeae, which colonized the New World at least twice-during the mid-Miocene and Pliocene. Edaphic conditions and intolerance of soil acidity may be factors that restricted the distribution of most genera of Synandreae to southeastern and south-central North America, whereas polyploidy could have increased the colonizing capability of the more wide-ranging genus, Physostegia.
authors.affiliation: Department of Biological Sciences, University at Buffalo, Buffalo, NY, United States; Current affiliation: Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, United States.
authors.forename: Tilottama
authors.initials: T
authors.lastname: Roy
authors.affiliation: Department of Biological Sciences, University at Buffalo, Buffalo, NY, United States; Current affiliation: Department of Biology, University of Florida, Gainesville, FL, United States.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Catlin
authors.affiliation: Department of Biological Sciences, University at Buffalo , Buffalo , NY , United States.
authors.forename: Drake M G
authors.initials: DM
authors.lastname: Garner
authors.affiliation: Department of Environmental and Plant Biology, Ohio University , Athens , OH , United States.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Cantino
authors.affiliation: Museum of Archaeology, University of Stavanger , Stavanger , Norway.
authors.forename: Anne-Cathrine
authors.initials: AC
authors.lastname: Scheen
authors.affiliation: Department of Biological Sciences, University at Buffalo , Buffalo , NY , United States.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Lindqvist
keywords: Biogeography; Lamiaceae; North America; Nuclear markers; Phylogeny; Physostegia; Stachydeae; Synandreae