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Tethyan plant disjunctions, including Mediterranean-African-Asian disjunctions, are thought to be vicariant, but their temporal origin and underlying causes remain largely unknown. To address this issue, we reconstructed the evolutionary history of Smilax aspera, a hypothesized component of the European Tertiary laurel forest flora. Thirty-eight populations and herbarium specimens representing 57 locations across the species range were sequenced at seven plastid regions and the nuclear ribosomal internal transcribed spacer region. Time-calibrated phylogenetic and phylogeographic inferences were used to trace ancestral areas and biogeographical events. The deep intraspecific split between Mediterranean and African-Asian lineages is attributable to range fragmentation of a southern Tethyan ancestor, as colder and more arid climates developed shortly after the mid-Miocene. In the Mediterranean, climate-induced vicariance has shaped regional population structure since the Late Miocene/Early Pliocene. At around the same time, East African and South Asian lineages split by vicariance, with one shared haplotype reflecting long-distance dispersal. Our results support the idea that geographic range formation and divergence of Tertiary relict species are more or less gradual (mostly vicariant) processes over long time spans, rather than point events in history. They also highlight the importance of the Mediterranean Basin as a centre of intraspecific divergence for Tertiary relict plants., (© 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.)

Arabis alpina is a characteristic plant in arctic-alpine habitats and serves as a classical example to demonstrate biology, ecology and biogeography of arctic-alpine disjuncts. It has a wider distribution than most other arctic-alpine plants, covering all European mountain systems, the Canary Islands, North Africa, the high mountains of East Africa and Ethiopia, the Arabian Peninsula and mountain ranges of Central Asia in Iran and Iraq. Additionally it is found in the northern amphi-Atlantic area including northeastern North America, Greenland, Iceland, Svalbard and northwestern Europe. We used markers from the nuclear (internal transcribed spacer of ribosomal DNA) and chloroplast genome (trnL-F region) to reconstruct its phylogeographic history. Both markers revealed clear phylogeographic structure. We suggest that A. alpina originated in Asia Minor less than 2 million years ago based on synonymous mutation rates of different genes (plastidic matK, nuclear adh and chs). From the Asian ancestral stock one group migrated via the Arabian Peninsula to the East African high mountains. A second group gave rise to all European and northern populations, and also served as source for the northwest African populations. A third group, which is still centred in Asia, migrated independently southwards and came into secondary contact with the East African lineage in Ethiopia, resulting in high genetic diversity in this area. In the Mediterranean regions, the genetic diversity was relatively high with numerous unique haplotypes, but almost without geographic structure. In contrast, the populations in the northern amphi-Atlantic area were extremely depauperate, suggesting very recent (postglacial) expansion into this vast area from the south.