Abstract
The delimitation of Himatanthus (Apocynaceae) species has long been problematic, and much confusion remains as to which names and species delimitations should be adopted. In order to recognize and clarify the species of Himatanthus occurring in Peru, herbarium specimens were examined, coupled with detailed field observations. The present study recognizes three species in Peru: H. revolutus, H. tarapotensis and H. phagedaenicus. A key to identify the species, as well as descriptions, synonymy, specimens cited, and taxonomic comments are presented.
Highlights
Himatanthus Willdenow ex Roemer & Schultes (1819: xiii; Apocynaceae) is currently recognized as a neotropical genus of nine species, characterized by alternate leaves, presence of colleters in the axils of the petiole and at the base of the floral bracts; terminal, thyrsoid inflorescences consisting of dichotomous cincinni with a reduced axis subtended by two deciduous, petaloid floral bracts, corolla infundibuliform, sinistrorsely convolute, stamens inserted near the base of corolla tube, anthers free from the style head, gynoecium hemi-syncarpous composed of two carpels, style head cylindrical or obconical with two round apices, ovary semi-inferior without nectariferous disc, two opposite, woody follicles, and seeds with a concentric wing (Spina 2004, Spina et al 2013)
Endress et al (2014) confirmed the position of the genus in tribe Plumerieae, subtribe Plumeriinae, along with Plumeria Linnaeus (1753: 209) and Mortoniella Woodson (1939: 257–259). These three genera have the following common characteristics: semi-inferior ovary, style head without a basal collar, and absence of a nectariferous disk (Endress & Bruyn 2000, Woodson 1937), and can be distinguished from each other by the characteristics cited by Woodson (1937, 1939, 1948), Plumel (1990, 1991), and Morales (2005)
As the monophyly of Himatanthus has never been tested with molecular phylogenies, the generic delimitations proposed by Woodson (1937, 1939), Plumel (1990, 1991), Spina (2004), Spina et al (2013), and Endress et al (2014) are here adopted, and the species delimitations of Spina (2004) and Spina et al (2013) are followed
Summary
Himatanthus Willdenow ex Roemer & Schultes (1819: xiii; Apocynaceae) is currently recognized as a neotropical genus of nine species, characterized by alternate leaves, presence of colleters in the axils of the petiole and at the base of the floral bracts; terminal, thyrsoid inflorescences consisting of dichotomous cincinni with a reduced axis subtended by two deciduous, petaloid floral bracts, corolla infundibuliform, sinistrorsely convolute, stamens inserted near the base of corolla tube, anthers free from the style head, gynoecium hemi-syncarpous composed of two carpels, style head cylindrical or obconical with two round apices, ovary semi-inferior without nectariferous disc, two opposite, woody follicles, and seeds with a concentric wing (Spina 2004, Spina et al 2013). Endress and Bruyn (2000) positioned Himatanthus in subfamily Rauvolfioideae (= Plumerioiodeae), tribe Plumerieae, along with nine other genera. Plumel proposed several new combinations in Himatanthus, and recognized 13 species and eight varieties in the genus. As the monophyly of Himatanthus has never been tested with molecular phylogenies, the generic delimitations proposed by Woodson (1937, 1939), Plumel (1990, 1991), Spina (2004), Spina et al (2013), and Endress et al (2014) are here adopted, and the species delimitations of Spina (2004) and Spina et al (2013) are followed.
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