Sphinctanthus fluvii-dulcis (Rubiaceae: Gardenieae), a new species from the Rio Doce Valley, Atlantic forest of Minas Ge
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ISSN: 0075-5974 (print) ISSN: 1874-933X (electronic)
Sphinctanthus fluvii-dulcis (Rubiaceae: Gardenieae), a new species from the Rio Doce Valley, Atlantic forest of Minas Gerais, Brazil, with detailed observations on ovary morphology Piero G. Delprete1 & Claes Persson2
Summary. A new species of Sphinctanthus from the Rio Doce Valley, Atlantic forest in the state of Minas Gerais, Brazil, is here described and illustrated. The species is peculiar within the genus by having placentation entirely parietal, while in the other species of Sphinctanthus the placentation is basally axial and distally parietal. In addition, despite its bright orange flowers (being a plant with high potential as an ornamental), it is only known from two collections from nearby localities, indicating that it is a rare and critically endangered species. Resumo. Uma nova espécie de Sphinctanthus proveniente do Vale do Rio Doce, na Floresta Atlantica do Estado de
Minas Gerais, Brasil, é aqui descrita e ilustrada. A espécie é peculiar dentro do gênero por ter placentação completamente parietal, em quanto que nas outras espécies a placentação é basalmente axial e distalmente parietal. Também, apesar das flores de cor laranja vivo (sendo uma planta com alto potencial de ser cultivada como ornamental), ela é conhecida somente por duas coletas em localidades muito proximas, indicando que é uma espécie rara e criticamente em perigo. Key Words. Placentation, taxonomy.
Introduction Sphinctanthus Benth. was originally described by Bentham (1841), and its generic name refers to the corolla tube constricted below the mouth of the type species. The genus comprises four or five South American species of shrubs and small trees. It has hermaphroditic flowers, cream-white, yellow, yellowish orange to bright orange corollas, corolla tube with a ring of hairs at the middle or near the base inside, corolla lobes contorted to the left, and triporate pollen grains released in monads (Persson 1993, p. 578, fig. 8A – B). The only exception to this set of characters would be Sphinctanthus insignis Steyerm. (Steyermark 1981), which has white corollas lacking a ring of hairs inside and caudate lobes; however, this species most likely belongs to the genus Randia L. (C. Gustafsson, pers. comm.). Phylogenetic analyses using molecular data confirmed that Sphinctanthus belongs to the tribe Gardenieae (Persson 2000) and positioned it as the sister genus of Rosenbergiodendron Fagerl. (Gustafsson & Persson 2002). As of today, Sphinctanthus has been treated only in regional floras (e.g. Schumann 1889; Steyermark 1972, 1974). The
only taxonomic revision available for Sphinctanthus is an unpublished undergraduate thesis, produced at the University of Gothenburg (Wallberg 1999). During routine identification of Brazilian Rubiaceae, a recent collection from the municipality of Belo Oriente, Minas Gerais state, attracted our attention because of the bright orange flowers and other morphological features that pointed to the genus Sphinctanthus. In fact, another specimen from a nearby localit
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