OM Grace, S Buerki, MRE Symonds, F Forest, AE Van Wyk, GF Smith, RR Klopper, CS Bjora, S Neale, S Demissew, MSJ Simmonds, N Rønsted (2015) Evolutionary history and leaf succulence as explanations for medicinal use in aloes and the global popularity of Aloe vera. BMC Evolutionary Biology 15: 29 PDF
What’s it about?
We carried out a phylogenetic analysis of almost 200 species of aloes, those (mostly) waxy thick leaves (sometimes slightly prickly) plants whose most famous member is the ubiquitous body-gel/conditioner/ointment ingredient Aloe vera. We found significant phylogenetic signal in medicinal use and leaf succulence in the genus (indicating that medicinal properties tend to me found in certain clades) and further that the two traits are evolutionarily correlated. Species of aloes which appear to have ‘lost’ medicinal utility are those that have lost leaf succulence. Our analysis also suggests that the particular reason why Aloe vera is so popular as a health-care product is due to a fortuitous combination of having been abundant in Arabia and the Middle East at about the time when this was one of the main trade-hubs of the world, and of being relatively unusually for Arabian aloes (most others don’t have medicinal properties), even though aloes more generally in Africa (where the majority of aloes are from) do have plenty of medicinal uses.
What’s the story behind it?
This paper continued the collaboration I’ve had with Nina Rønsted (see here for another paper) looking at evolution of medicinal properties in plants. This is mostly the ample work of Olwen Grace, a former postdoc of Nina’s, now at the Royal Botanic Gardens in Kew. Essentially I was the person called in to do the analysis of phylogenetic signal and the phylogenetic comparative analysis of coevolution of leaf succulence and medicinal use. It ended up being a really nice paper, expertly marshalled by Olwen. We almost got it accepted in another higher-impact publication (I won’t name it but it rhymes with moss seedlings of the loyal sobriety), but one reviewer really got fixated with one aspect of the analysis they didn’t like and it ended up just falling in front of the line, Devon Loch-style. When it went to BMC Evolutionary Biology it returned with the two most glowingly positive reviews I think I’ve ever seen. Gah, where were you lovely reviewers first time round! Actually BMC Evol Biol have done a lovely job with making the paper look nice – and free!