title: Evolution of leaf anatomy in arid environments - A case study in southern African Tetraena and Roepera (Zygophyllaceae).
abstract: The dry biomes of southern Africa (Desert, Nama Karoo and Succulent Karoo) are home to a rich and diverse xerophytic flora. This flora includes two morphologically diverse clades of Zygophyllaceae, Tetraena and Roepera (Zygophylloideae), which inhabit some of the most arid habitats in the region. Using a plastid phylogeny of Zygophylloideae we assess whether the evolution of putatively adaptive traits (leaf shape, vasculature, mode of water storage and photosynthetic type: C3 versus C4) coincides with the successful colonisation of environments with different drought regimes within southern Africa. Our results show general niche conservatism within arid habitats in Tetraena, but niche shifts from arid to more mesic biomes with longer and/or cooler growing season (Fynbos and Thicket) in Roepera. However, these distinct broad-scale biogeographical patterns are not reflected in leaf anatomy, which seems to vary at more local scales. We observed considerable variability and multiple convergences to similar leaf anatomies in both genera, including shifts between "all cell succulence" leaf types and leaf types with distinct chlorenchyma and hydrenchyma. Our survey of C4 photosynthesis in the Zygophylloideae showed that the C4 pathway is restricted to Tetraena simplex, which also having an annual life history and a widespread distribution, is rather atypical for this group.
authors.affiliation: Institut für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany. Electronic address: mlauter@uni-mainz.de.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Lauterbach
authors.affiliation: Department of Biochemistry, University of Stellenbosch, Stellenbosch, South Africa.
authors.forename: Pieter de Wet
authors.initials: PW
authors.lastname: van der Merwe
authors.affiliation: Institut für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Keßler
authors.affiliation: Institut für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany; Department of Biochemistry, University of Stellenbosch, Stellenbosch, South Africa.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Pirie
authors.affiliation: Department of Biochemistry, University of Stellenbosch, Stellenbosch, South Africa.
authors.forename: Dirk U
authors.initials: DU
authors.lastname: Bellstedt
authors.affiliation: Institut für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Kadereit
mesh_terms: D000353:Africa, Southern; D005075:Biological Evolution; D003889:Desert Climate; D055864:Droughts; D017753:Ecosystem; D010641:Phenotype; D010788:Photosynthesis; D010802:Phylogeny; D058974:Phylogeography; D018515:Plant Leaves / Q000033:anatomy & histology*; D018087:Plastids / Q000235:genetics; D028461:Zygophyllaceae / Q000033:anatomy & histology* / Q000145:classification* / Q000235:genetics
keywords: C(4) photosynthesis; Molecular phylogeography; NGS marker screening; Nama Karoo and Succulent Karoo; Zygophyllum