Historical biogeography conjectures that cladogenesis, the origins of species and lineages of organisms, is directly related to geographic migration and isolation of clade members over time. The geologic and environmental history of the Northern Hemispher e shows great consistency with most organismal phylogenies that have so far been produced. Barriers to plant migration have been created and lifted alternately throughout the Tertiary and Quaternary, leading to some general geographic patterns that are re peatedly recovered in phylogenetic studies of disparate flowering plant groups.
The project will utilize members of the monophyletic mint subfamily Lamioideae (Leppeblomstfamilien) to uncover phylogenetic evidence for episodic environmental changes, part icularly with reference to transatlantic versus transberingian relationships, intracontinental disjunctions, hybrid cladogenesis, and the interglacial invasion of Fennoscandia. Results of the project will form a case study toward the development of a mode l for mosaic evolution of the Northern Hemisphere flora, and will advance knowledge of the phylogeny and taxonomy of a species-rich and ecologically important lineage of the mint family.