Abstract Detail

Biogeography

Mugizi, Tusiime Felly [1], Gizaw, Abel [2], Wondimu, Tigist [3], Masao, Catherine Aloyce [4], Abdi, Ahmed Abdikadir [5], Muwanika, Vincent [1], Travnicek, Pavel [6], Nemomissa, Sileshi [3], Popp, Magnus [7], Eilu, Gerald [1], Brochmann, Christian [8], Pimentel, Manuel [9].

African mountains conquered twice, followed by plastid capture and polyploidization: the intriguing history of the sweet vernal grasses (Anthoxanthum L. Poaceae; Pooideae).

The enigmatic flora of the tropical high mountains in Africa is thought to have different geographical affinities, but the phylogenetic and phylogeographic history of most lineages are still poorly known. Southwards as well as northwards relationships have been proposed for the polyploid Anthoxanthum species complex of eastern Africa (A. nivale and A. aethiopicum). Here we aim to reconstruct the phylogeny to test the hypotheses on the origin(s) of this complex and to infer its phylogeographic history. Dated Bayesian phylogenies based on nuclear and plastid DNA were constructed in order to unravel the evolutionary relationship between A. nivale and A. aethiopicum. The phylogeography of A. nivale was assessed through the analysis of ploidy levels and genetic diversity of 125 plants (35 populations) from the entire distribution range using flow cytometry and Amplified Fragment Length Polymorphisms. The East African A. nivale was not monophyletic with respect to the Ethiopian A. aethiopicum. The western mountains A. nivale samples (Western Rift Zone, WRZ+ Elgon) were closely related to the European and Ethiopian Anthoxanthum species; whereas the eastern mountains lineage (Eastern Rift Zone, ERZ) formed a polytomy with the South African and Malagasy taxa in the plastid phylogeny. Genetic diversity was higher in the western mountains than in the eastern mountains. Three major DNA-content groups representing two divergent lineages on either sides of the Rift Valley were found within A. nivale: G1 + G2 in the western, and G3 in the eastern mountains. Almost no gene flow was inferred across the Rift Valley. Conclusions The East African Anthoxanthum complex was inferred to have originated from a Eurasian ancestor that first colonised East Africa and later radiated to the Ethiopian Highlands. There it diversified and generated A. aethiopicum, a taxon whose status as a species is supported by our results. A putative secondary contact involving chloroplast capture took place in the eastern mountains between A. nivale and the South African and Malagasy complex of the genus, which explains the incongruence observed in the phylogenies. The East African Rift Valley has played a fundamental role in shaping the evolutionary relationships and distribution of genetic diversity in the East African Anthoxanthum. We found an almost complete isolation between the mountain systems situated in both sides of the Rift Valley. DNA content and geography (mountain systems) account for most of the genetic variation observed.

1 - Makerere University, Department of Forestry, Biodiversity and Tourism, Makerere University PO Box 7062, Kampala, 7062, Uganda
2 - University of Oslo, Natural History Museum, PO Box 1172 Blindern, Oslo, NO-0318, Norway
3 - Addis Ababa University, Plant Biology and Biodiversity Management, Addis Ababa University PO Box 3434, Addis Ababa, 3434, Ethiopia
4 - Sokoine University of Agriculture, Department of Forest Biology, Sokoine University of Agriculture PO Box 3010, Morogoro, 3010, Tanzania
5 - National Museums of Kenya, East African Herbarium, National Museums of Kenya PO Box 40658-00100, Nairobi, 40658-00100, Kenya
6 - Institute of Botany, Department of Flow Cytometry, Institute of Botany CZ-252 43 , Pruhonice, CZ-252 43, Czech Republic
7 - University Of Oslo, The Natural History Museums & Botanical Garden, P.O. Box 1172 Blindern, Oslo, NO-0318, Norway
8 - University Of Oslo, National Centre For Biosystematics, P.O. Box 1172 Blindern, Oslo, N/A, NO-0318, Norway
9 - University of A Coruña, Plant Biology, Animal Biology and Ecology, Faculty of Sciences, Campus da Zapateira sn, A Coruña, E15008, Spain

Keywords:
afro-alpine
Anthoxanthum nivale
Anthoxanthum aethiopicum
Rift Valley
Phylogeography
phylogeny.

Presentation Type: Oral Paper
Session: 30, Biogeography I
Location: 203/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 2:30 PM
Number: 30005
Abstract ID:144
Candidate for Awards:None