title: Sweet vernal grasses (Anthoxanthum) colonized African mountains along two fronts in the Late Pliocene, followed by secondary contact, polyploidization and local extinction in the Pleistocene.
abstract: High tropical mountains harbour remarkable and fragmented biodiversity thought to a large degree to have been shaped by multiple dispersals of cold-adapted lineages from remote areas. Few dated phylogenetic/phylogeographic analyses are however available. Here, we address the hypotheses that the sub-Saharan African sweet vernal grasses have a dual colonization history and that lineages of independent origins have established secondary contact. We carried out rangewide sampling across the eastern African high mountains, inferred dated phylogenies from nuclear ribosomal and plastid DNA using Bayesian methods, and performed flow cytometry and AFLP (amplified fragment length polymorphism) analyses. We inferred a single Late Pliocene western Eurasian origin of the eastern African taxa, whose high-ploid populations in one mountain group formed a distinct phylogeographic group and carried plastids that diverged from those of the currently allopatric southern African lineage in the Mid- to Late Pleistocene. We show that Anthoxanthum has an intriguing history in sub-Saharan Africa, including Late Pliocene colonization from southeast and north, followed by secondary contact, hybridization, allopolyploidization and local extinction during one of the last glacial cycles. Our results add to a growing body of evidence showing that isolated tropical high mountain habitats have a dynamic recent history involving niche conservatism and recruitment from remote sources, repeated dispersals, diversification, hybridization and local extinction.
authors.affiliation: School of Forestry, Geographical and Environmental Sciences, Department of Forestry, Biodiversity and Tourism, Makerere University, Kampala, Uganda.|Natural History Museum, University of Oslo, Oslo, Norway.
authors.forename: Felly Mugizi
authors.initials: FM
authors.lastname: Tusiime
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.|Department of Plant Biology and Biodiversity Management, Addis Ababa University, Addis Ababa, Ethiopia.
authors.forename: Abel
authors.initials: A
authors.lastname: Gizaw
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.|Department of Plant Biology and Biodiversity Management, Addis Ababa University, Addis Ababa, Ethiopia.
authors.forename: Tigist
authors.initials: T
authors.lastname: Wondimu
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.|Department of Forest Biology, Sokoine University of Agriculture, Morogoro, Tanzania.
authors.forename: Catherine Aloyce
authors.initials: CA
authors.lastname: Masao
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.|National Museums of Kenya, Nairobi, Kenya.
authors.forename: Ahmed Abdikadir
authors.initials: AA
authors.lastname: Abdi
authors.affiliation: School of Forestry, Geographical and Environmental Sciences, Department of Forestry, Biodiversity and Tourism, Makerere University, Kampala, Uganda.
authors.forename: Vincent
authors.initials: V
authors.lastname: Muwanika
authors.affiliation: Department of Flow Cytometry, Institute of Botany, Průhonice, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Trávníček
authors.affiliation: Department of Plant Biology and Biodiversity Management, Addis Ababa University, Addis Ababa, Ethiopia.
authors.forename: Sileshi
authors.initials: S
authors.lastname: Nemomissa
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.
authors.forename: Magnus
authors.initials: M
authors.lastname: Popp
authors.affiliation: School of Forestry, Geographical and Environmental Sciences, Department of Forestry, Biodiversity and Tourism, Makerere University, Kampala, Uganda.
authors.forename: Gerald
authors.initials: G
authors.lastname: Eilu
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.
authors.forename: Christian
authors.initials: C
authors.lastname: Brochmann
authors.affiliation: Natural History Museum, University of Oslo, Oslo, Norway.|CICA, Centro de Investigacións Científicas Avanzadas, Universidade da Coruña, Galicia, Spain.
authors.forename: Manuel
authors.identifier: http://orcid.org/0000-0003-4452-6584
authors.initials: M
authors.lastname: Pimentel
mesh_terms: D000352:Africa, Northern; D054458:Amplified Fragment Length Polymorphism Analysis; D001499:Bayes Theorem; D005075:Biological Evolution; D010802:Phylogeny; D058974:Phylogeography; D006109:Poaceae / Q000145:classification*
keywords: Africa; colonization; hybridization; polyploidization; tropical-alpine