Historical Isolation versus Recent Long-Distance Connections between Europe and Africa in Bifid Toadflaxes (Linaria sect. Versicolores)

Abstract

BackgroundDue to its complex, dynamic and well-known paleogeography, the Mediterranean region provides an ideal framework to study the colonization history of plant lineages. The genus Linaria has its diversity centre in the Mediterranean region, both in Europe and Africa. The last land connection between both continental plates occurred during the Messinian Salinity Crisis, in the late Miocene (5.96 to 5.33 Ma).Methodology/Principal FindingsWe analyzed the colonization history of Linaria sect. Versicolores (bifid toadflaxes), which includes c. 22 species distributed across the Mediterranean, including Europe and Africa. Two cpDNA regions (rpl32-trnLUAG and trnK-matK) were sequenced from 66 samples of Linaria. We conducted phylogenetic, dating, biogeographic and phylogeographic analyses to reconstruct colonization patterns in space and time. Four major clades were found: two of them exclusively contain Iberian samples, while the other two include northern African samples together with some European samples. The bifid toadflaxes have been split in African and European clades since the late Miocene, and most lineage and speciation differentiation occurred during the Pliocene and Quaternary. We have strongly inferred four events of post-Messinian colonization following long-distance dispersal from northern Africa to the Iberian Peninsula, Sicily and Greece.Conclusions/SignificanceThe current distribution of Linaria sect. Versicolores lineages is explained by both ancient isolation between African and European populations and recent events of long-distance dispersal over sea barriers. This result provides new evidence for the biogeographic complexity of the Mediterranean region.

The Evolutionary Fate of the Horizontally Transferred Agrobacterial Mikimopine Synthase Gene in the Genera Nicotiana and Linaria

“…Our estimate of the age of the most recent common ancestor of L. vulgaris , L. dalmatica and L. genistifolia is in accordance with the estimates reported by other authors [43],[71]. Since the Linaria mis is degenerated in all species studied, it is likely that the mis sequence started to degenerate soon after the HGT.…”

Multiple windows of colonization to Macaronesia by the dispersal-unspecialized Scrophularia since the Late Miocene

“…Given that Scrophularia fossils have not been discovered to date, the Scrophulariaceae root height was modelled as a normal distribution with mean 26.77 Ma (SD = 4.27 Ma). These values were obtained from a previous temporal calibration of a ndhF phylogeny (Navarro-Pérez et al, 2013), which included minimum stem-age constraints for Lamiales families and tribes based on five fossils (see Vargas et al, 2014;Fernández-Mazuecos and Vargas, 2011 for details). The GTR + I + G and GTR + G models for ITS and concatenated plastid regions, respectively, were selected according to the Akaike Information Criterion (AIC) implemented in jModelTest 2.1.3 (Darriba et al, 2012).…”

Horizontal gene transfer from Agrobacterium to plants

“…Linaria includes about 150 species that are widely spread in the Palearctic region, but the representatives of the genus are the most variable in the Mediterranean basin. The origin of the genus has been placed in the Miocene era (Fernandez-Mazuecos and Vargas, 2011) predating the Messinian Salinity Crisis (Hsu et al, 1977). The latest classification of the genus Linaria accepts seven sections ( Linaria, Speciosae, Diffusae, Supinae, Pelisserianae, Versicolores, and Macrocentrum ) (Sutton, 1988).…”