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.
Highlights
Studying the role of biogeographic barriers as limiting factors for plant range expansion and gene flow allows investigation of the causes behind population differentiation and speciation (e. g. [1,2])
Accessions of the same species or subspecies were retrieved as monophyletic groups only for L. elegans, L. nigricans, L. multicaulis subsp. galioides, L. pedunculata and L. bipartita, while polyphyly was clearly retrieved for L. incarnata, L. gharbensis, L. multicaulis subsp. heterophylla and L. tingitana
We explicitly designed a morphological and geographic sample to overcome methodological issues associated with the complex taxonomy of Linaria
Summary
Studying the role of biogeographic barriers as limiting factors for plant range expansion and gene flow allows investigation of the causes behind population differentiation and speciation (e. g. [1,2]). The abundance of islands, peninsulas, straits and mountains, and the complex history of climate and sea-level changes have created changing opportunities for plant dispersal and colonization across different barriers [3,4]. The Messinian Salinity Crisis (MSC), in the late Miocene (5.96 to 5.33 Ma) [5] has long been considered the last major window of opportunity for plant colonization across the Mediterranean [6]. Desiccation of the Mediterranean Sea during this age formed land bridges that facilitated plant range expansion, including colonization events between Africa and Europe Dynamic and well-known paleogeography, the Mediterranean region provides an ideal framework to study the colonization history of plant lineages. The last land connection between both continental plates occurred during the Messinian Salinity Crisis, in the late Miocene (5.96 to 5.33 Ma)
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