Comparative floral micromorphology and anatomy of species of Bulbophyllum section Napelli (Orchidaceae), a Neotropical section widely distributed in forest habitats ELAINE L. P. NUNES 1 *, ERIC C. SMIDT 2 , THOMAS STÜTZEL 3 and ALESSANDRA IKE COAN 1 1 Programa de Pós-Graduação em Ciências Biológicas (Biologia Vegetal), Instituto de Biociências de Rio Claro, Universidade Estadual Paulista – UNESP, C. Postal 199, CEP 13506-900 Rio Claro, São Paulo, Brazil 2 Departamento de Botânica, Setor de Ciências Biológicas, Universidade Federal do Paraná, C. Postal 19031, CEP 81530-900 Curitiba, Paraná, Brazil 3 Lehrstuhl für Evolution und Biodiversität der Pflanzen, Ruhr-Universität Bochum, Universitätstraße 150, Bochum 44780, Germany Received 14 July 2014; revised 29 November 2014; accepted for publication 26 December 2014 Bulbophyllum section Napelli, as recently circumscribed based on molecular analyses, comprises 12 species. These occur as epiphytes in the Brazilian Atlantic Rain Forest and in gallery forests in the cerrado vegetation, and thus differ from other Neotropical sections of Bulbophyllum, which are more variable in habit and habitat. To identify diagnostic characteristics that are representative of this section and to confirm whether there are characteristics that are related to their habit and habitat, their floral micromorphology and anatomy were studied using conventional techniques. Bulbophyllum section Napelli is characterized by sepals with sunken glandular trichomes and stomata on the abaxial surface, reduced petals with one vascular bundle (sometimes lacking), an entire labellum with a secretory sulcus on the adaxial surface and a keel with stomata or glandular trichomes on the abaxial surface, two pollinia, and crystalliferous idioblasts in all floral parts. Our data enable us to distinguish between species and show congruence with the present circumscription of B. section Napelli. The labellar epidermal surface of three closely-related species was unusual in its possession of unicellular trichomes and these appear to function as osmophores. A relationship between striate surfaces, iridescence and pollinator attraction related to the epiphytic habit and forest habitat is proposed. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177, 378–394. ADDITIONAL KEYWORDS: Bulbophyllum atropurpureum – Bulbophyllum campos-portoi – Bulbophyllum granulosum – Bulbophyllum malachadenia – Bulbophyllum regnellii – cell wall striation – nectary – petal reduction osmophore – secretory epidermis. INTRODUCTION The genus Bulbophyllum Thouars is represented by 62 species in the Neotropics that were recently allocated to six monophyletic sections, based mostly on molecu- lar data. The sections are Bulbophyllum section Bul- bophyllaria (Rchb.f.) Griseb., Bulbophyllum section Furvescens E.C.Smidt, Borba & Van den Berg, Bulbo- phyllum section Napelli Rchb.f., Bulbophyllum section Micranthae Barb.Rodr., Bulbophyllum section Didac- tyle (Lindl.) Cogn., and Bulbophyllum section Xiphi- zusa (Rchb.f.) Cogn. (Smidt et al., 2011). Most species occur both as epiphytes and lithophytes in open and wooded areas of the cerrado, Atlantic Rain Forest, *Corresponding author. E-mail: elaine.lopes@gmail.com Botanical Journal of the Linnean Society, 2015, 177, 378–394. With 7 figures © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177, 378–394 378 Downloaded from https://academic.oup.com/botlinnean/article/177/3/378/2416457 by guest on 16 February 2023