Origins of East Asian Campanuloideae (Campanulaceae) diversity

Abstract

The Campanulaceae comprises approximately 2300 species that are distributed among five major lineages: Campanuloideae, Cyphioideae, Cyphocarpoideae, Lobelioideae, and Nemacladoideae. Of these, the Campanuloideae, a primarily Old World clade, has the largest diversity in East Asia. In this study, we reconstruct the phylogeny of East Asian Campanuloideae based on one nuclear gene (i.e., PPR70) and five plastid markers (i.e., atpB, matK, petD, rbcL, and trnL-trnF). We then use this phylogenetic framework to reconstruct the biogeographical history of the genus. Our molecular dataset includes 376 of the 1045 currently recognized species in the Campanuloideae. Of the 376 sampled species, 116 are from East Asia, representing ca. 60% of the East Asian Campanuloideae. Our PPR dataset included sequences for 156 accessions, representing 54 species, while our plastid dataset included sequences for 305 accessions, representing 354 species. Phylogenetic analyses recovered three large clades containing East Asian taxa: Campanulinae, Platycodinae, and Wahlenberginae. The historical assembly of Campanuloideae diversity in East Asia appears to have resulted from numerous, independent movements from Africa, Europe/W. Asia, and North America. Africa was inferred as the ancestral range for the Campanuloideae. Movement of the largest East Asian clade (Platycodinae) occurred at approximately 53.1 Ma (46.6–58.73 95% HPD) from Africa, with much of the current diversity found in East Asia having resulted from in situ diversification. Thirteen additional movements into East Asia, primarily from Europe/Western Asia, occurred subsequently. One dispersal event from western North America was also inferred. In contrast, only six movements out of East Asia were found. Our results suggest that East Asia has acted primarily as a sink for Campanuloideae diversity, with Europe, Western Asia, and Africa representing major source areas.