Three New Species of the Megadiverse Genus Microlicia (Melastomataceae) with Notes on Leaf Anatomy

Abstract

Abstract— The new species Microlicia arenaria, M. dentisepala, and M. membranacea are described from the Diamantina Plateau, Minas Gerais state, Brazil. Microlicia arenaria is a cespitose subshrub with xylopodium, fastigiate branches, forming clumps, sessile leaves, linear lamina, and hypanthium and sepals covered with golden spherical glands. In addition, it has dimorphic and bicolored stamens with tetrasporangiate anthers. Microlicia dentisepala has a subshrub or shrub habit, is erect and much branched, and its leaves are small, varnished in appearance, with both surfaces covered with spherical glands. The sepals are triangular to narrowly lanceolate and shorter than the length of the hypanthium, with a tooth aspect. Microlicia membranacea is a subshrub with petiolate leaves, lamina of membranous consistency and suprabasal venation, with prominent secondary veins. The branch, leaf, hypanthium, and sepals are covered with glandular trichomes, and the cylindrical hypanthium is slightly contracted at the apex. Microlicia arenaria and M. dentisepala exhibit some anatomical features common to Microlicia, such as amphistomatic leaves, short-stalked glandular trichomes in depressions on the leaf surface, compact mesophyll, phenolic compounds in the subepidermal layer, idioblasts with druses in the mesophyll, and collateral vascular bundles. Microlicia membranacea stands out by its hypostomatic leaves and a thin mesophyll formed by only three to four cell layers, conditions possibly related to a shaded environment. Following the criteria of the Red List of the International Union for Conservation of Nature (IUCN), we preliminarily assess the conservation status of the species Microlicia arenaria as Endangered (EN), Microlicia dentisepala as Critically Endangered (CR), and Microlicia membranacea as Data Deficient (DD). We provide descriptions of the new species, along with field images, detailed illustrations, and comparisons with related species. Data on geographic distribution and habitat are also presented.