Insights on the systematics and morphology of Humiriaceae (Malpighiales): androecial and extrafloral nectary variation, two new combinations, and a new Sacoglottis from Guyana

Abstract

Humiriaceae have had little recent comparative morphological study except for their distinctive fruits. We surveyed the diversity of stamen structures in the family with consideration of dehiscence patterns and the evolutionary transitions between tetra- and disporangiate anthers. Novel interpretations of floral morphology support new combinations (Duckesialiesneri K.Wurdack & C.E.Zartman, comb. nov. and Vantaneaspiritu-sancti K.Wurdack & C.E.Zartman, comb. nov.) for two species formerly in Humiriastrum. We investigated all eleven species of Sacoglottis for diagnostic features that may contribute to better species delimitations, and describe Sacoglottisperryi K.Wurdack & C.E.Zartman, sp. nov. as an endemic of the Pakaraima Mountains in western Guyana. Finally, our survey across Humiriaceae for extrafloral nectaries (EFNs) revealed their presence on leaves of all extant species as adaxial basilaminar and/or abaxial embedded glands, in addition to the frequent occurrence of marginal glandular setae. The significance of inter-generic variation in gland position and anther morphology within the family are discussed.

Evolution of connective glands reveals a new synapomorphy for Malpighiaceae and the hidden potential of staminal glands for Malpighiales systematics

“…Finally, the Salicoids had nectar connective glands recovered as a synapomorphy in our analysis. Nectar connective glands have recently been suggested as a new morphological synapomorphy for Humiriaceae ( Wurdack and Zartman 2019 ). However, this exudate is also recorded in the filament or connective glands of Violaceae within the Salicoids ( Feng 2005 ; Wurdack and Zartman 2019 ).…”

Flora of Espírito Santo: Humiriaceae

“…Inflorescences corymbose, terminal and axillary; peduncle 3-4 cm long, cylindrical, glabrescent. Flowers with pedicels 1-2 cm long, cylindrical, hirsute; sepals 1-1.5 × 1 mm, ovate, ciliate; petals 3-4 × 1-1.5 mm, deciduous, lanceolate, hirsute; stamens 20, Species endemic to Brazil, being restricted to the Atlantic Forest domain, occurring, until now, in the states of Bahia and Espirito Santo, where it is registered in vegetation of Dense Rainforest from low to high altitudes (Cuatrecasas 1964;BFG 2018;Wurdack & Zartman 2019;Tab. 1), with occurrence records in three conservation units: Goiapaba-Açu Environmental Proctetion Area, Vale Nature Reserve and Augusto Ruschi Biological Reserva.…”

“…1), with occurrence records in three conservation units: Goiapaba-Açu Environmental Proctetion Area, Vale Nature Reserve and Augusto Ruschi Biological Reserva. Vantanea spiritu-sancti was recently transferred from the genus Humiriastrum to Vantanea, for presenting anthers with two bisporangiate thecae and palynological characteristics (Wurdack & Zartman 2019). The species has a greater morphological similarity with V. bahiaensis, whose morphological delimitation was presented in the comments of that species.…”

“…Humiriaceae belongs to Malpighiales (APG IV 2016) and has 65 species in eight genera, of which Endopleura and Hylocarpa are represented by only one species (Wurdack & Zartman 2019). The family is almost exclusively Neotropical, occurring mainly in the tropical forests from southern Brazil to Central America (Cuatrecasas 1961), except for Sacoglottis gabonenses (Baill.)…”

“…Humiriaceae is composed mostly of shrubs or treelets, with alternate leaves having serrate (e.g., Humiriastrum and Sacoglottis) or entire (e.g., Humiria and Vantanea) leaf margins. The most important reproductive structure for genera and/or species delimitation is the morphological variation of the androecium (Wurdack & Zartman 2019).…”