Diversification into novel habitats in the Africa clade of Dioscorea Dioscoreaceae: erect habit and elephant’s foot tubersReport as inadecuate




Diversification into novel habitats in the Africa clade of Dioscorea Dioscoreaceae: erect habit and elephant’s foot tubers - Download this document for free, or read online. Document in PDF available to download.

BMC Evolutionary Biology

, 16:238

Phylogenetics and phylogeography

Abstract

BackgroundDioscorea is a widely distributed and highly diversified genus in tropical regions where it is represented by ten main clades, one of which diversified exclusively in Africa. In southern Africa it is characterised by a distinct group of species with a pachycaul or -elephant’s foot- structure that is partially to fully exposed above the substrate. In contrast to African representatives of the genus from other clades, occurring mainly in forest or woodland, the pachycaul taxa and their southern African relatives occur in diverse habitats ranging from woodland to open vegetation. Here we investigate patterns of diversification in the African clade, time of transition from forest to more open habitat, and morphological traits associated with each habitat and evaluate if such transitions have led to modification of reproductive organs and mode of dispersal.

ResultsThe Africa clade originated in the Oligocene and comprises four subclades. The Dioscorea buchananii subclade southeastern tropical Africa and South Africa is sister to the East African subclade, which is respectively sister to the recently evolved sister South African e. g., Cape and Pachycaul subclades. The Cape and Pachycaul subclades diversified in the east of the Cape Peninsula in the mid Miocene, in an area with complex geomorphology and climate, where the fynbos, thicket, succulent karoo and forest biomes meet.

ConclusionsDiversification out of forest is associated with major shifts in morphology of the perennial tuber specifically an increase in size and orientation which presumably led them to become pachycaul and rotation of stem from twining to non-twining. The iconic elephant-s foot morphology, observed in grasslands and thicket biomes, where its corky bark may offer protection against fire and herbivory, evolved since mid Miocene. A shift in pollination trait is observed within the forest, but entry into open habitat does not show association with reproductive morphology, except in the seed wing, which has switched from winged all round the seed margin to just at the base or at the apex of it, or has been even replaced by an elaiosome.

KeywordsBiogeography Dioscoreales -elephant’s foot- Fire adaptation Habitat transition Pachycaul Southern Africa Yams AbbreviationsCLCompound-Leaved

CTABHexadecyltrimethylammonium bromide

ILDIncongruence Length Difference

NWINew World I clade

NWIINew World II clade

Xdh nuclear region XdhNewly Sequenced Nuclear Gene

Electronic supplementary materialThe online version of this article doi:10.1186-s12862-016-0812-z contains supplementary material, which is available to authorized users.

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Author: Olivier Maurin - A. Muthama Muasya - Pilar Catalan - Eugene Z. Shongwe - Juan Viruel - Paul Wilkin - Michelle van der Ban

Source: https://link.springer.com/







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