Comparative Phylogeography and Conservation Genetics of Some Afro-Montane Plant Species From Ethiopian and Tropical East African Mountains As Inferred From Aflp
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Date
2007-07
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Addis Ababa University
Abstract
The afro-alpine region s.l. refers to the high mountains of Ethiopian and Topical East Africa.
The flora of this region is unique in composition compared to the surrounding lowlands and
subdivided into three altitudinal vegetation belts: the afro-montane, ericaceous and afro-alpine
belts. The origin and extant distribution of the flora had been influenced strongly by the
Pleistocene climatic oscillations. During glacial (cold) periods, the afro-alpine and ericaceous
belts were broad while the afro-montane belt was reduced and fragmented. The montane
forests had probably persisted in refugia located at mountain foothills or in river basins. Afromontane
forest was extensive during interglacial (warm) periods whereas the afro-alpine and
ericaceous belts were compact. Based on amplified fragment length polymorphisms (AFLPs)
data, we provide insights into the origin, fragmentation and evolution of some key afromontane
species in relation to Pleistocene climatic oscillations. In view of this, we focus on
the genetic diversity and population genetic structure of these afro-montane plant taxa without
obvious long distance dispersal morphology and that are widely distributed in the East
African mountain systems (i.e., Erica arborea, Hypericum revolutum and Lobelia giberroa).
Regardless of some general observed phylogeographic trends such as divergent lineages,
contact zones, altitudinal shift and complex refugia, our analyses highlight that each species
had a unique phylogeographic pattern and the geographical consistency of the genetic patterns
differ considerably. Our observation further suggest that L. giberroa and H. revolutum genetic
groups occupied geographically well defined areas while the geographic pattern of E.
arboreia is rather complex. Furthermore, we have attempted to identify important areas for
conservation of the current study species based on concepts of hotspots of intraspecific
diversity and evolutionary significant units (ESU). This approach could be followed to assess
or design appropriate genetic conservation priorities as well as a robust sampling strategiesfor further studies. This study is the first of its kind concerning the impacts of Pleistocene
glaciations on the genetic structures of afro-montane/-alpine plants and it will certainly guide
to scope future phylogeographic studies in Africa. In prospect, it is important to cover the
whole distribution range of the study species to have more complete phylogeographic picture
of the region. In addition, it is appropriate to investigate many wide-spread plant species with
well-documented fossil data and use appropriate genetic criteria to deduce the impact of
Pleistocene climatic fluctuations on the genetic structure of the present day afro-montane/-
alpine flora.
Key words: AFLP, Afro-alpine, Afro-montane, Conservation, Erica arborea, Hypericum
revolutum, Lobelia giberroa, Phylogeography
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Keywords
AFLP, Afro-alpine, Afro-montane, Conservation, Erica arborea, Hypericum revolutum, Lobelia giberroa, Phylogeography