title: Colonization and diversification in the African 'sky islands': insights from fossil-calibrated molecular dating of Lychnis (Caryophyllaceae).
abstract: The flora on the isolated high African mountains or 'sky islands' is remarkable for its peculiar adaptations, local endemism and striking biogeographical connections to remote parts of the world. Ages of the plant lineages and the timing of their radiations have frequently been debated but remain contentious as there are few estimates based on explicit models and fossil-calibrated molecular clocks. We used the plastid region maturaseK (matK) and a Caryophylloflora paleogenica fossil to infer the age of the genus Lychnis, and constructed a data set of three plastid (matK; a ribosomal protein S16 (rps16); and an intergenic spacer (psbE-petL)) and two nuclear (internal transcribed spacer (ITS) and a region spanning exon 18-24 in the second largest subunit of RNA polymerase II (RPB2)) loci for joint estimation of the species tree and divergence time of the African representatives. The time of divergence of the African high-altitude Lychnis was placed in the late Miocene to early Pliocene. A single speciation event was inferred in the early Pliocene; subsequent speciation took place sporadically from the late Pliocene to the middle Pleistocene. We provide further support for a Eurasian origin of the African 'sky islands' floral elements, which seem to have been recruited via dispersals at different times: some old, as in Lychnis, and others very recent. We show that dispersal and diversification within Africa play an important role in shaping these isolated plant communities.
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.|Department of Plant Biology and Biodiversity Management, College of Natural Science, Addis Ababa University, PO Box 3434, Addis Ababa, Ethiopia.
authors.forename: Abel
authors.initials: A
authors.lastname: Gizaw
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.
authors.forename: Christian
authors.initials: C
authors.lastname: Brochmann
authors.affiliation: Department of Plant Biology and Biodiversity Management, College of Natural Science, Addis Ababa University, PO Box 3434, Addis Ababa, Ethiopia.
authors.forename: Sileshi
authors.initials: S
authors.lastname: Nemomissa
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.|Department of Plant Biology and Biodiversity Management, College of Natural Science, Addis Ababa University, PO Box 3434, Addis Ababa, Ethiopia.
authors.forename: Tigist
authors.initials: T
authors.lastname: Wondimu
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.|Department of Forest Biology, Sokoine University of Agriculture, PO Box 3010, Morogoro, Tanzania.|Institute of Resource Assessment, University of Dar es Salaam, Box 35097, Dar es Salaam, Tanzania.
authors.forename: Catherine Aloyce
authors.initials: CA
authors.lastname: Masao
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.|Department of Forestry Biodiversity and Tourism, School of Forestry Geographical and Environmental Sciences, Makerere University, PO Box 7062, Kampala, Uganda.
authors.forename: Felly Mugizi
authors.initials: FM
authors.lastname: Tusiime
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.|Botany Department, National Museums of Kenya, PO Box 40658, 00100, Nairobi, Kenya.
authors.forename: Ahmed Abdikadir
authors.initials: AA
authors.lastname: Abdi
authors.affiliation: Department of Biology and Environmental Sciences, University of Gothenburg, PO Box 461, 405 30, Gothenburg, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Oxelman
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.
authors.forename: Magnus
authors.initials: M
authors.lastname: Popp
authors.affiliation: Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.
authors.forename: Dimitar
authors.initials: D
authors.lastname: Dimitrov
mesh_terms: D000349:Africa; D002138:Calibration; D018744:DNA, Plant / Q000235:genetics; D005580:Fossils; D056426:Genetic Loci; D005843:Geography; D031244:Lychnis / Q000235:genetics*; D010802:Phylogeny; D055110:Radiometric Dating; D013045:Species Specificity
chemical_list: D018744:DNA, Plant
keywords: African mountains; Lychnis; diversification; molecular dating; origin of high-altitude lineages