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| Euphorbia pseudodidiereoides J.-P. Castillon & Rajaovelona, G-H) E. didiereoides in Castillon & Rajaovelona, 2019. |
Abstract
A new species of spiny, multi-stemmed spurge, Euphorbia pseudodidiereoides J.-P. Castillon & Rajaovelona, is described and illustrated here. It is known only from the Ihorombe region, south central Madagascar, and occurs on an isolated quartzite massif surrounded by vast grasslands and granite inselbergs. Its presumed nearest relative is E. didiereoides Denis ex Leandri, with which it shares many common characters, including: general V-shaped habit reminiscent of some species of the genus Alluaudia (Drake) Drake (Didiereaceae), thick stems, numerous spines, rarely solitary, densely arranged, of variable size (5-25 mm), without alignment, green pubescent leaves, elliptic with a mucronate apex, without petiole but bearing a white thick mid-vein, capitate incyathescences, and pubescent peduncle. It differs from E. didiereoides by its shorter size (0.8-1.5 m vs 2-4 m for adult individuals), recumbent branches, and an incyathescence with shorter peduncle (1.5 cm instead of 8 cm), less dense cymes with fewer cyathia (8-16 cyathia instead of 20-60), and wider, rounded, 8x8 mm cyatophylls. This new species is assessed to be Critically Endangered according to IUCN Red List Categories and Criteria because it is only known from a single unprotected locality, with the number of mature individuals being less than 250 and a measurable decline in local natural habitat (CR B1 ab(iii,v) + 2 ab(iii,v); C2 a(ii)).
Key words: Euphorbia, new species, Goniostema, Ihorombe, Madagascar
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A) Sobennikoffia humbertiana, B-F) Euphorbia pseudodidiereoides, G-H) E. didiereoides |
Euphorbia pseudodidiereoides, J.-P. Castillon & Rajaovelona, species nova
Diagnose: Haec planta Euphorbia didieroides affinisest sed sequentibus characteribus praecipue differt :minore statura (<1,5 m) ; longis caulibus inclinatisad terram ; capitatis inflorescentiis minus densis (8-16 cyathis contra 20-60) ; cyathorum foliis latioribusrotundatisque
Jean-Philippe Castillon and Landy Rita Rajaovelona. 2019. Euphorbia pseudodidiereoides, une nouvelle euphorbe épineuse du Centre-sud de Madagascar [A New Spiny Spurge from south-central Madagascar] Malagasy Nature. 13: 60–64.
http://www.vahatra.mg/volume13/MN13_03_Castillon.pdf
