Multiple origins of dwarf shrubs on the African high mountains

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Alpine and arctic environments worldwide, including high mountains, are dominated by short-stature woody plants (dwarf shrubs). This conspicuous life form asserts considerable influence on local environmental conditions above the treeline, creating its own microhabitat.

Distribution of Afrotemperate (Afromontane and Afroalpine) regions in Africa adapted from Gehrke and Linder (2014) based on White (1983).
Distribution of Afrotemperate (Afromontane and Afroalpine) regions in Africa adapted from Gehrke and Linder (2014) based on White (1983). Full details in Gehrke et al. (2015)

Gehrke et al. show that the dwarf shrub life form evolved at least twice under alpine-like conditions in African Alchemilla (lady’s mantles). The independent evolution of dwarf shrubs in Alchemilla, that they date to as recent as the Pleistocene, highlights a selective advantage. However, despite ecological success and alpine speciation it did not trigger increased rates of diversification. They also infer reversals from (partial) woodiness back to entirely herbaceous forms, a transition rarely reported in angiosperms.

Reference

Gehrke, B., Kandziora, M., & Pirie, M. D. (2015). The evolution of dwarf shrubs in alpine environments: a case study ofAlchemillain Africa. Annals of Botany, 117(1), 121–131. http://dx.doi.org/10.1093/aob/mcv159


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