Brasilianthus (Melastomataceae), a new monotypic genus endemic to ironstone outcrops in the Brazilian Amazon

Abstract

A new monotypic genus, Brasilianthus carajensis, is described from Carajás Mineral Province where it is restricted to campo rupestre vegetation on ironstone outcrops (canga) that form island-like lenses nestled in the Amazon rainforest of southeastern Pará, Brazil. Among neotropical capsular-fruited Melastomataceae, Brasilianthus is distinguished by a unique combination of characters: annual habit; haplostemonous, 4-merous flowers; tubulose-subcylindric hypanthia with erect, narrowly obovate deciduous calyx lobes that are widest distally and well-spaced basally; short cupulate-campanulate anthers with a wide truncate apical pore; biaristate ventral staminal appendages; 4-locular ovary with an apex crowned by four persistent ± deltoid appendages; absence of placental intrusions in mature capsules; and subcochleate seeds with a costate testa. These morphological characters are congruent with DNA sequence data that show Brasilianthus nested within the Marcetia alliance of the tribe Melastomeae where it is sister to Nepsera aquatica. These two genera are in turn sister to Ernestia pullei and Appendicularia thymifolia. A comprehensive description of Brasilianthus is presented together with diagnostic illustrations, images of plants in the wild, a distribution map, SEM images of seeds, a geospatial conservation assessment based on IUCN criteria, and comparisons with generic relatives in the Marcetia alliance.Key words: haplostemony, Marcetia alliance, phylogeny, Serra dos Carajás, canga ResumoUm novo gênero monotípico, Brasilianthus carajensis, é descrito da Província Mineral de Carajás, onde é restrito à vegetação de campo rupestre sobre afloramentos ferruginosos (canga), que formam ilhas rupestres na floresta amazônica no sudeste do estado do Pará, Brasil. Entre as espécies de Melastomataceae neotropicais com frutos capsulares, Brasilianthus distinguese por uma combinação única de caracteres: hábito anual; flores tetrâmeras haplostêmones; hipanto tubuloso e subcilíndrico com lobos do cálice eretos, decíduos, estreitamente obovais, com a parte distal mais larga e base claramente espassada; anteras curtas, cupulado-campanuladas com um amplo poro apical truncado; apêndices ventrais estaminais biaristados; ovário tetralocular, com um ápice coroado por quatro apêndices ± deltóides persistentes; ausência de intrusões da placenta em cápsulas maduras; e sementes subcocleadas com testa costada. Estas características morfológicas são congruentes com os dados de sequência de DNA que mostram Brasilianthus inseridos na aliança Marcetia da tribo Melastomeae, onde é grupo irmão de Nepsera aquatica. Estes dois gêneros são, por sua vez, grupo irmão de Ernestia pullei e Appendicularia thymifolia. Uma descrição completa de Brasilianthus é apresentada, assim como ilustrações diagnósticas, imagens das plantas no habitat, micrografia eletrônica de varredura de sementes, uma avaliação do estado de conservação com base em critérios da IUCN, e comparações com gêneros relacionados na aliança Marcetia.

A Monograph of the Brazilian endemic genus Lavoisiera (Melastomataceae: Microlicieae)

“…The advent of scanning electron microscopy (SEM) has heightened its usefulness as evidenced by several publications that have assessed the systematic significance of seed morphology at the tribal, generic, and species levels (Whiffin & Tomb 1972;Almeda 1993;Renner 1994;Martin et al 2008;Almeda & Robinson 2011;Ocampo & Almeda 2013;Goldenberg et al 2015;Almeda et al 2016). We studied the micromorphology of seeds for selected species of Lavoisiera using the SEM.…”

“…The latter shows periclinal walls of testa cells that are convex and more fully collapsed concave cells in close proximity on the same seed. Martins (1989) also reported the presence of concavities and convexities in the periclinal walls of the seed testa in selected species of Marcetia Candolle (1828: 124), one of 13 genera currently assigned to the Marcetia alliance of the tribe Melastomeae (Michelangeli et al 2013;Almeda et. al.…”

Flora das cangas da Serra dos Carajás, Pará, Brasil: história, área de estudos e metodologia

“…1l, Isoetaceae) (Pereira et al 2016) (Salas et al 2015) and Brasilianthus carajasensis Almeda & Michelangeli (Fig. 1e,Melastomataceae) (Almeda et al 2016), two new monospecific genera. Even though new taxa were described, the bulk of the Carajás collections remained in herbaria, awaiting to be studied in systematically and in detail.…”

“…The gaps in scientific knowledge throughout the biome are a result of sparse collecting effort, with less than 0.18 herbarium specimens collected by square kilometer in northern Brazil (BFG 2015;Nic Lughadha & Morim 2015) . Nonetheless, several new taxa were recently described following specific efforts carried out in isolation, such as the survey of the Parque Estadual do Cristalino, in northern Mato Grosso (e.g., Vanderplank & Zappi 2011;Frisby & Hind 2014), the Serra do Aracá (e.g., Grant et al 2006;Michelangeli & Goldenberg 2014) and the Reserva Ducke, in Amazonas (e.g., Lombardi 2007;Boeira et al 2012;Souza et al 2015), Serra do Cachimbo (Harley 2013) and the Serra dos Carajás, in the state of Pará (e.g., Dittrich et al 2014;Salino et al 2014;Salas et al 2015;Araujo & Chautems 2015;Almeda et al 2016;Pereira et al 2016;Nunes et al 2016).…”

A Guide to Curating New World Melastomataceae Collections with a Linear Generic Sequence to World-Wide Melastomataceae

“…A strictly neotropical and recently described tribe that includes some 20 genera of mostly herbaceous South American species formerly in the Melastomateae and one genus formerly in the Microlicieae (Rocha et al 2016a, Rocha et al 2018. Several generic realignments, resurrections, and descriptions have occurred across of the tribe (Almeda et al 2016, Rocha et al 2018. Monotypic Mallophyton is assigned here based on morphology.…”