Spermacoceae s. str.: Delimitation of the genus Staelia, rehabilitation of Tessiera and description of a new genus from the central Planalto of Brazil (Rubiaceae)

SALAS, R. M.; CABRAL, E. L.

Xalapa, Veracruz, Mexico

Conferencia; IV International Rubiaceae Conference.; 2008

National Botanic Garden (Belgium)

During the study of the American genus Staelia Cham. & Schltdl. we noticed that some species classified in this genus do not exhibit its diagnostic characters, perhaps reflecting the paraphyletic nature of Staelia. Therefore, we studied all species included in Staelia to determine which of them fit in Staelia s.str. and to relocate the remaining taxa in other genera of Spermacoceae. The most problematic species are the ones endemic to Mexico. In order to determine the relationships between the species we studied the type specimens and found that Tessiera and Diphragmus are homotypic synonyms. In spite of the close historical relationship between Tessiera, Diphragmus and Staelia, contemporary authors treated Tessiera and Diphragmus as synonyms of Spermacoce L. and not of Staelia. In order to contribute to the clear separation of these taxa, we studied pollen morphological, carpological and seed morphological characters. We noticed that the Mexican species display many differences that we consider sufficient to separate them from Staelia. Therefore, we propose to rehabilitate the genus Tessiera with the election of T. lithospermoides DC. as type species. A new combination is made too and a new species is described from Acapulco, Mexico. Finally, another group of species, which includes two endemic taxa of the Central Brazilian high plateau, is excluded from Staelia; we propose to include them in a new genus. Consequently, we present the description of this new genus and we discuss its differences from the potentially related Spermacoceae genera. Two new combinations are made and a new species is described, endemic to the state of Goiás, Brazil.