Out of the Mediterranean Region: worldwide biogeography of snapdragons and relatives (tribe Antirrhineae, Plantaginaceae)

Abstract

AimThe tribe Antirrhineae, including snapdragons, toadflaxes and relatives, is a model group for plant evolutionary research. It is widely distributed across the Northern Hemisphere and the Neotropics, but displays an uneven distribution of diversity, with more than 50% of species and subspecies in the Mediterranean Region. Here we conducted the first detailed, worldwide biogeographic analysis of the Antirrhineae and tested two alternative hypotheses (time-for-speciation vs. diversification rate differences) to explain the uneven distribution of diversity. LocationWorldwide, with a focus on the Mediterranean Region. Taxontribe Antirrhineae (Plantaginaceae). MethodsA phylogenetic biogeographic approach was taken, accounting for area connections through time. Ancestral ranges, dispersal events, speciation and lineage accumulation within areas were estimated. Diversification rates for taxa present and absent in the Mediterranean Region were compared, accounting for the effect of a floral key innovation (nectar spur). ResultsA proto-Mediterranean origin in the Late Eocene was estimated, and the Mediterranean Region stood out as the main centre for speciation and dispersal. Congruent patterns of long-distance dispersal from the Mediterranean Region to North America were recovered for at least two amphiatlantic clades. A significant floristic exchange between the Mediterranean and south-western Asia was detected. We found no evidence of different diversification rates between lineages inside and outside the Mediterranean Region. Main conclusionsThe Mediterranean Region played a key role in the origin of the current distribution of the Antirrhineae. However, the higher species richness found in this region appears to be the result of a time-for-speciation effect rather than of increased diversification rates. The establishment of current mediterranean climates in the Northern Hemisphere appears to have contributed to the recent diversification of the group, in combination with colonisation of adjacent regions with arid and semi-arid climates.