Monday, September 12, 2016

[Botany • 2016] Brasilianthus carajensis • A New Monotypic Genus (Melastomataceae) Endemic to Ironstone Outcrops in the Brazilian Amazon


Brasilianthus carajensis 
Almeda & Michelangeli 

FIGURE 3. Images of Brasilianthus carajensis. A. Brasilianthus carajensis on canga substrate. B. Habit of mature unpigmented plant. C. Habit of mature pigmented plant. D. Flowers with pale, nearly white, petals. E. Flower (at anthesis) with typical lilac/lavender petals. F. Habit showing foliar posture and shape.  
All photographs by P.L.Viana. DOI: 10.11646/phytotaxa.273.4.3

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.

Keywords: haplostemony, Marcetia alliance, phylogeny, Serra dos Carajás, canga, Eudicots


Distinguished by its annual habit; haplostemonous, 4-merous flowers; tubulose-subcylindric hypanthium with erect, narrowly obovate calyx lobes; short cupulate-campanulate anthers with a wide apical pore; biaristate ventral staminal appendages; ovary apex crowned with four persistent erect ± deltoid appendages; 4-locular ovary; absence of placental intrusions; and subcochleate seeds with a prominently costate testa.


Etymology:― The generic name, Brasilianthus, combines the country name, Brasil, and the Greek work for a flower, “anthus.” The specific epithet, carajensis, emphasizes the limited geographic distribution of this monotypic genus in the Carajás Mineral Province of southeastern Pará. 


 Frank Almeda, Fabián A. Michelangeli and Pedro L. Viana. 2016. Brasilianthus (Melastomataceae), A New Monotypic Genus Endemic to Ironstone Outcrops in the Brazilian Amazon. Phytotaxa. 273(4); 269–282.
 DOI: 10.11646/phytotaxa.273.4.3

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