Synopsis of Hexasepalum (Rubiaceae), the priority name for Diodella and a new species from Brazil

• Autores: Cabaña Fader, Andrea Alejandra; Salas, Roberto Manuel; Dessein, Steven; Cabral, Elsa Leonor
• Año de publicación: 2016
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Systematic Botany, 2016, vol. 41, no. 2, p. 408-422.
• Materia: Diodia; Neotropics; Spermacoceae
• Institución: Universidad Nacional del Nordeste

Fil: Cabaña Fader, Andrea Alejandra. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentina.
Fil: Cabaña Fader, Andrea Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina.
Fil: Salas, Roberto Manuel. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentina.
Fil: Salas, Roberto Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina.
Fil: Dessein, Steven. Botanic Garden Meise; Bélgica.
Fil: Cabral, Elsa Leonor. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentina.
Fil: Cabral, Elsa Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina.
Hexasepalum is the priority name for Diodella. In the present paper, we provide a synopsis of Hexasepalum. The genus differs from the remaining genera of the tribe Spermacoceae by the combination of infundibuliform flowers, 2-lobed stigmas, schizocarpic fruits, ventral face of the mericarps with two depressions, seeds with T or Y shaped ventral grooves, and pollen grains with two types of supratectal elements. We propose two combinations, i.e. Hexasepalum domingense and H. vaginale, and the formal synonymization of H. angustifolium (including Diodella crassifolia). We also propose two new synonyms: Diodia rosmarinifolia [= Diodella rosmarinifolia] is placed in the synonymy of H. apiculatum, andDiodia incana is now considered a synonym of H. teres. We choose lectotypes for H. vaginale, and for two synonyms of H. apiculatum. In addition, we describe and illustrate a new species endemic from Bahia, Brazil, H. zappiae sp. nov. Detailed descriptions are provided only for the species imperfectly known; otherwise comprehensive taxonomic descriptions are mentioned for each species. The descriptions of the Hexasepalum species are complemented with a key, geographical distributions, and illustrations of key morphological characters. Line drawings are provided for species not illustrated before in literature.