title: Evolutionary history and leaf succulence as explanations for medicinal use in aloes and the global popularity of Aloe vera.
abstract: BACKGROUND
  Aloe vera supports a substantial global trade yet its wild origins, and explanations for its popularity over 500 related Aloe species in one of the world's largest succulent groups, have remained uncertain. We developed an explicit phylogenetic framework to explore links between the rich traditions of medicinal use and leaf succulence in aloes.
  
  
  RESULTS
  The phylogenetic hypothesis clarifies the origins of Aloe vera to the Arabian Peninsula at the northernmost limits of the range for aloes. The genus Aloe originated in southern Africa ~16 million years ago and underwent two major radiations driven by different speciation processes, giving rise to the extraordinary diversity known today. Large, succulent leaves typical of medicinal aloes arose during the most recent diversification ~10 million years ago and are strongly correlated to the phylogeny and to the likelihood of a species being used for medicine. A significant, albeit weak, phylogenetic signal is evident in the medicinal uses of aloes, suggesting that the properties for which they are valued do not occur randomly across the branches of the phylogenetic tree.
  
  
  CONCLUSIONS
  Phylogenetic investigation of plant use and leaf succulence among aloes has yielded new explanations for the extraordinary market dominance of Aloe vera. The industry preference for Aloe vera appears to be due to its proximity to important historic trade routes, and early introduction to trade and cultivation. Well-developed succulent leaf mesophyll tissue, an adaptive feature that likely contributed to the ecological success of the genus Aloe, is the main predictor for medicinal use among Aloe species, whereas evolutionary loss of succulence tends to be associated with losses of medicinal use. Phylogenetic analyses of plant use offer potential to understand patterns in the value of global plant diversity.
authors: Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey, London, TW9 3DS, UK. o.grace@kew.org.|Natural History Museum of Denmark, University of Copenhagen, Sølvgade 83 Entrance S, DK1307, Copenhagen K, Denmark. o.grace@kew.org.
authors: Olwen M
authors: OM
authors: Grace
authors: Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK. s.buerki@nhm.ac.uk.
authors: Sven
authors: S
authors: Buerki
authors: Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, 221 Burwood Highway, Burwood, Victoria, 3125, Australia. matthew.symonds@deakin.edu.au.
authors: Matthew R E
authors: MR
authors: Symonds
authors: Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey, London, TW9 3DS, UK. f.forest@kew.org.
authors: Félix
authors: F
authors: Forest
authors: Department of Plant Science, H.G.W.J. Schweickerdt Herbarium, University of Pretoria, Pretoria, 0002, South Africa. braam.vanwyk@up.ac.za.
authors: Abraham E
authors: AE
authors: van Wyk
authors: Biosystematics Research & Biodiversity Collections Division, South African National Biodiversity Institute, Private Bag X101, Pretoria, 0001, South Africa. G.Smith@sanbi.org.za.|Department of Botany, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth, 6031, South Africa. G.Smith@sanbi.org.za.|Departamento de Ciências da Vida, Centre for Functional Ecology, Universidade de Coimbra, 3001-455, Coimbra, Portugal. G.Smith@sanbi.org.za.
authors: Gideon F
authors: GF
authors: Smith
authors: Department of Plant Science, H.G.W.J. Schweickerdt Herbarium, University of Pretoria, Pretoria, 0002, South Africa. R.Klopper@sanbi.org.za.|Biosystematics Research & Biodiversity Collections Division, South African National Biodiversity Institute, Private Bag X101, Pretoria, 0001, South Africa. R.Klopper@sanbi.org.za.
authors: Ronell R
authors: RR
authors: Klopper
authors: Natural History Museum, University of Oslo, PO Box 1172, Blindern, NO-0318, Oslo, Norway. charlotte.bjora@nhm.uio.no.
authors: Charlotte S
authors: CS
authors: Bjorå
authors: Centre for Middle Eastern Plants, Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK. s.neale@cmep.org.uk.
authors: Sophie
authors: S
authors: Neale
authors: Department of Plant Biology and Biodiversity Management, National Herbarium, College of Natural Sciences, Addis Ababa University, PO Box 3434, Addis Ababa, Ethiopia. sebseb.demissew@gmail.com.
authors: Sebsebe
authors: S
authors: Demissew
authors: Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey, London, TW9 3DS, UK. m.simmonds@kew.org.
authors: Monique S J
authors: MS
authors: Simmonds
authors: Natural History Museum of Denmark, University of Copenhagen, Sølvgade 83 Entrance S, DK1307, Copenhagen K, Denmark. nronsted@snm.ku.dk.
authors: Nina
authors: N
authors: Rønsted
mesh_terms: D000349:Africa; D000504:Aloe / Q000145:classification / Q000235:genetics* / Q000502:physiology; D005075:Biological Evolution; D008877:Middle East; D010802:Phylogeny; D018515:Plant Leaves / Q000502:physiology*; D010946:Plants, Medicinal / Q000145:classification / Q000235:genetics / Q000502:physiology