Biogeographic analysis based on phylogenomic data supports multiple ancient dispersals that facilitated the eastern Asia–North America–Mexico disjunction in the subfamily Linnaeoideae (Caprifoliaceae)

Abstract

The small subfamily Linnaeoideae of Caprifoliaceae exhibits a disjunct distribution in Eurasia and North America, including Mexico, with most taxa occurring in eastern Asia or Mexico and the monospecific Linnaea Gronov. ex L. having a circumboreal to north temperate distribution. We sampled 17 of the 20 species representing all Linnaeoideae genera and used nuclear (target enrichment) and complete plastome sequence data to reconstruct the phylogeny. Our results show strong topological conflicts between nuclear and plastid data, especially concerning Dipelta Maxim. and Diabelia Landrein, supporting hybridization events complicating the deep diversification. Nuclear data were used for divergence time estimation and ancestral area reconstruction. The divergence time between the Mexican Vesalea M. Martens & Galeotti and the Linnaea clade was dated to 39.5 Ma, with a 95% highest posterior density of 28.2 Ma (mid‐Oligocene) to 45.2 Ma (mid‐Eocene). Reconstructed ancestral areas support a widespread common ancestor of Linnaea plus Vesalea in Mexico and at least another area (eastern Asia, North America, or Europe). The biogeographic analysis, including fossils, supports the ancestral range of Linnaeoideae to be widespread in central and western China + Europe + Mexico, or eastern and northern Asia + central and western China + Mexico, or central and western China + North America + Mexico. The North Atlantic and/or the Bering land bridges may be important in the widespread distribution across continents in the Northern Hemisphere. Our study highlights the importance of utilizing fossils in biogeographic inferences andusing data from different genomes while reconstructing deep and shallow phylogenies of organisms.