During a field investigation in open deciduous woodlands covered by lava outcrops in Makueni County, southern Kenya in September, 2018, a shrubby Euphorbia with densely stellate hairs on abaxial leave surface attracted the attention of the research team. Thereafter, the researchers revisited the area, performed more careful observations on its morphological characters, and collected enough specimens for further study.
Supervised by Prof. WANG Qingfeng and Prof. HU Guangwan, PhD student WEI Neng from the Wuhan Botanical Garden of the Chinese Academy of Sciences carried out the study of comprehensive morphology and molecular phylogeny around this Euphorbia.
After sufficient literature consultant, specimens examinations, detailed morphological comparisons, as well as robust phylogenetic support, this species was finally confirmed to be new to science and named 'mbuinzauensis' for the type locality. Results were published in Phytokeys.
Morphologically, Euphorbia mbuinzauensis is most similar to E. pseudomollis, but differs mainly by its shrubby habit, abaxial leaves surfaces with densely stellate hairs, 2-4-forked cymes, smaller bracts, smaller cyathia, crimson glands without narrow smooth margin, smaller fruits and ovoid seeds.
Euphorbia mbuinzauensis is distinct from other species in Synadenium group with strong morphological and phylogenetic support. Using phylogenetic inference based on a nrDNA dataset, the previously segregated genus Synadenium is tested as monophyly. Nevertheless, an expand and dense sampling of closely related species is needed to draw this conclusion with greater confidence.
It is worth mentioning that the phylogenetic relationships among the species in Synadenium group exhibite extremely short branches, indicating that this lineage is likely to have radiated very recently.
According to the criteria of the International Union for Conservation of Nature, the new species is assessed as "endangered", given the very limited populations and individuals in the wild. Action is urgently needed, including in situ and ex situ conservation, to protect this fragile and lovely succulent.
Morphological features of Euphorbia mbuinzauensis. (Image by WEI Neng)
The maximum likelihood tree inferred from the complete nuclear ribosomal DNA sequences. (Image by WEI Neng)
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