Mabea dalyana (Euphorbiaceae-Hippomaneae): a new subshrub with xylopodia endemic to the savannas of the Brazilian Amazon

Abstract

During fieldwork in the Campos Amazônicos National Park, Amazonas state, Brazil, a new endemic species of Mabea was collected in savanna areas. Field collections and specimens in RON, MG, and HRCB were analyzed. To understand the species distribution and verify possible areas of occurrence, niche modeling was conducted using the sdm package in R. Mabea dalyana, the new species is a subshrub with xylopodia and reduced size (less than 1 m height) and small, yellow thyrses. There are several allopatric species of Mabea growing in Amazonian savannas, some widespread but others locally restricted, such as M. uleana from central Amazonia that has some superficial resemblance in leaves and inflorescences but can be distinguished from M. dalyana by pubescent adaxial leaf surface (vs. glabrous), 12-21 submarginal glands (vs. 10 submarginal glands), thyrse brownish to red (vs. yellow thyrse) and conspicuous caruncle (vs. caruncle inconspicuous). M. dalyana is endemic to hyperseasonal savanna, very well adapted to savanna, and fire tolerant. It has notable characteristics, such as a subshrub habit, a xylopodium, glabrous leaves, and sepals noticeably larger than the ovary.