The premise of the Study
A key question in evolutionary biology is why some clades are more successful by being widespread geographically, biome diverse, or species-rich. To extend an understanding of how shifts in area, biomes, and pollinators impact diversification in plants, we examined the relationships of these shifts to diversification across the mega-genus Salvia.
Methods
A chronogram was developed from a supermatrix of anchored hybrid enrichment genomic data and targeted sequence data for over 500 of the nearly 1000 Salvia species. Ancestral areas and biomes were reconstructed using BioGeoBEARS. Pollinator guilds were scored, ancestral pollinators determined, shifts in pollinator guilds identified, and rates of pollinator switches compared.
Key Results
A well-resolved phylogenetic backbone of Salvia and updated subgeneric designations are presented. Salvia originated in Southwest Asia in the Oligocene and subsequently dispersed worldwide. Biome shifts are frequent from a likely ancestral lineage utilizing broadleaf and/or coniferous forests and/or arid shrublands. None of the four species diversification shifts are correlated to shifts in biomes. Shifts in the pollination system are not correlated to species diversification shifts, except for one hummingbird shift that precedes a major shift in diversification near the crown of the New World subgenus. Calosphace. Multiple reversals back to bee pollination occurred within this hummingbird clade.
Conclusions
Salvia diversified extensively in different continents, biomes, and with both bee and bird pollinators. The lack of tight correlation of area, biome, and most pollinator shifts to the four documented species diversification shifts points to other important drivers of speciation in Salvia.
