Brasilianthus carajensis, Almeda & Michelangeli, 2016

Almeda, Frank, Michelangeli, Fabián A. & Viana, Pedro L., 2016, Brasilianthus (Melastomataceae), a new monotypic genus endemic to ironstone outcrops in the Brazilian Amazon, Phytotaxa 273 (4), pp. 269-282 : 272-279

Brasilianthus carajensis, Almeda & Michelangeli , gen. et sp. nov. ( Figures 2–3 , 4 A–C )

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.

Type : Brazil. Pará: Canaã dos Carajás, FLONA de Carajás, Serra dos Carajás, Serra do Tarzan, 6°19’31”S, 50°06’01”W, 702 m, 1 May 2015, P. L. Viana, A. Gil, N. F. O. Mota, A. L. Ilkiu-Borges & C. S. Nunes 5720 (holotype: MG!; isotypes: BHCB!, CAS!, K!, NY!, RB!) .

Delicate, wiry annual herbs 4–38 cm tall, mostly sparingly and openly branched distally. Cauline internodes commonly red like the petioles, hypanthia, and some older leaf blades, quadrangular and carinate to narrowly and obscurely winged at least distally, sparsely hirtellous with smooth spreading gland-tipped trichomes 0.2–0.3 mm long. Nodes with a distinct but inconspicuous interpetiolar line, glabrous or with a few gland-tipped trichomes like those on the internodes. Leaves opposite, isomorphic in size and shape in each pair. Basal leaves early deciduous and typically not present on flowering or fruiting plants. Cauline leaves membranaceous to somewhat fleshy when fresh; petioles 1–2.5 mm long, sparingly beset with spreading gland-tipped trichomes 0.1–0.2 mm long; blades green on both surfaces, widely spreading, 4–20 × 0.5–3.2 mm, linear-oblong to narrowly oblanceolate, 1–3-nerved, apex obtuse to bluntly rounded, base acute to attenuate, mostly glabrous on both surfaces but sometimes beset with a few scattered gland-tipped trichomes abaxially and small inconspicuous glandular trichomes mostly less than 0.5 mm long adaxially; the margins bluntly and distantly crenate to crenulate. Inflorescence a modified dichasium with widely spaced flowers that superficially appear solitary and terminal but also appearing lateral with the growth of axillary buds, the ultimate flowering branches elongating and becoming ± monochasial or superficially appearing somewhat pseudospiciform in fruit; pedicel 1 mm long at anthesis, the subtending leaves somewhat reduced in size but otherwise like the principal leaves. Flowers 4-merous and haplostemonous. Hypanthium (at anthesis) 3–4 × 1–1.5 mm, tubulose-subcylindric to narrowly obovoid, 8-ribbed, mostly glabrous and appearing alveolate when fresh but drying smooth and thinly papery. Calyx lobes 4, erect, 1.75–2.8 mm long, 0.5–0.75 mm wide distally at the widest point, narrowly obovate, glabrous on both surfaces, crenulate distally, commonly red at the constricted base, green and ± foliaceous distally, deciduous (sometimes tardily so) on mature hypanthia, spaced 0.5 mm apart on the torus at the distal end of the hypanthium at anthesis; calyx tube obsolete. Petals 1.9–2.9 × 0.9–2(–2.5) mm, obovate, lilac sometimes fading to a pale lilac or almost white, widely spreading at anthesis, glabrous throughout, entire and eciliate. Stamens 4 (these antesepalous), isomorphic; filaments 1.75–2 mm long, ± compressed, glabrous, lavender or lilac, declined to one side of the flower opposing the style; anthers 0.5 × 0.5 mm, purple, cupulate-campanulate, the wide ± truncate apical pore 0.5 mm across; connective not conspicuously thickened dorsally but prolonged 0.75 mm into an ivory-colored pedoconnective below the thecae, the pedoconnective geniculate with the filament insertion and modified at its juncture with the filament into an erect or incurved biaristate ventral appendage 1–1.5 mm long that is ivory-colored along the dilated base but lavender on the subulate distal lobes; staminodia absent. Ovary (at anthesis) superior, narrowly obovoid. Style 2–2.5 mm long, declined to one side of the flower opposing the stamens, lavender to mauve, stigma capitate and white when fresh but appearing capitellate when dry. Pedicels lengthening to 1.75–2 mm on fruiting hypanthia, glabrous. Mature hypanthia narrowly tubulose-subcylindric to narrowly campanulate, 5–6 × 2 mm, thin, papery, rupturing irregularly and flaking away with age. Mature loculicidal capsules 5–6 × 1.5–2 mm, 4-locular, prominent placental intrusions lacking (the seeds stacked in two vertical columns per locule), glabrous throughout and crowned with four persistent (but sometimes inconspicuous) erect ± deltoid appendages 0.5–0.75 mm long and 0.5–0.75 mm wide at the base that are apically acute to bluntly rounded. Seeds subcochleate and prominently costate on the chalazal side, beige to pale brown, 0.49–0.79 mm long and 0.43–0.54 mm high; lateral symmetrical plane elliptic, the highest point toward the chalazal side; antiraphal symmetrical plane elliptic. Raphal zone circular to widely obovate, ca. 50% of the length of the seed. Multicellular sculpture a pattern of longitudinal ridges on both the lateral and antiraphal sides. Cells arranged in an aligned pattern. Individual cells elongated, anticlinal boundaries raised and straight; periclinal walls flat and lacking microrelief. Cells in the areas between the ridges differing in having boundaries with a few clavate appendages or sometimes the boundaries not evident.

Phenology: ―Collected in flower and fruit from December through May. This is largely coincident with the rainy season in this part of the eastern Amazon which extends from December to April ( Piló et al. 2015).

Distribution and habitat: ―A majority of the 44 collections of Brasilianthus are from the easternmost region of the Serra dos Carajás ( Figure 5 ). This serra of pre-Cretaceous age is enclosed by the Araguaia and Itacaiúnas rivers. It is located about 540 km south of Belém in southeastern Pará, Brazil, and has an elevational range of 300 to 800 m ( Soubies et al. 1991; Silva 1993; Cleef & Silva 1994; Piló et al. 2015). On the Serra dos Carajás, this species can be locally common on the ferruginous ironstone upland ridges that are covered with iron breccia generically known as canga ( Piló et al. 2015). The word canga describes the open, rocky habitats with a savanna vegetation cover on iron ore outcrops that are nestled within the more widespread rainforest that covers much of the Carajás mountain range. Brasilianthus appears to grow only in these non-forest vegetation habitat islands that have been variously described as canga vegetation, banded ironstone formations (BIF), ferruginous shrubby or herbaceous campo rupestre, and even mettalophile savanna ( Nunes et al. 2015). Virtually all of the known collections come from habitats described as vegetação rupestre, campo graminoso on canga, and lake margins in canga. At the beginning of the rainy season it is often first noted along margins of lakes that dot this landscape at 580−760 m elevation.

An initial inventory of the vertebrate fauna of the Carajás National Forest has recently been completed and a plan for environmental diversity conservation has been proposed that addresses the search for compatibility between mineral exploration and biodiversity conservation (Martins et al. 2012). Information on the ecology and natural history of many vertebrate groups is still needed to adequately evaluate their conservation status. The flora of the forest and the canga uplands is diverse but it is imperfectly known and still being explored. The canga habitats, in particular, represent a unique isolated ecosystem in the Amazon and in Minas Gerais, Brazil, with high biodiversity and notable endemism ( Jacobi et al. 2007; Vincent & Meguro 2008; Golder Associates Brasil 2010; Oliveira et al. 2014; Skirycz et al. 2014; Piló et al. 2015; Salas et al. 2015).

Conservation status:―The distribution of Brasilianthus carajensis appears to be centered in the easternmost section of the Serra dos Carajás with two outlying populations in mountains somewhat west of this serra ( Figure 5 ). On the Serra dos Carajás, Brasilianthus occurs within the limits of a conservation area called the FLONA de Carajás (Carajás National Forest) that was established in early 1998 ( Figure 5 ). The Forest covers 411,949 ha of protected area ( Piló et al. 2015) but it allows certain types of usage, including mining activities. The open cast mining activities in the region present a major threat to its biodiversity because the iron ore deposits of the Serra are considered to be the largest in the world (Martins et al. 2012; Piló et al. 2015). Because only 3% of the over 400,000+ ha protected zone is covered by the canga habitat, urgent conservation management measures are needed to protect the high alpha and beta diversity of these extraordinary habitat islands ( Nunes et al. 2015; Piló et al. 2015). The few known collection localities for Brasilianthus outside of the FLONA de Carajás currently have no protected status. The extent of occurrence (EOO) for B. carajensis is 7,210.048 km ² and the area of occupancy (AOO) is 112 km ². Using IUCN guidelines and criteria and considering its archipelago-like distribution and restriction to canga islands, annual habit with potential for wide fluctuations in the number of maturing individuals each year, and ongoing threat of expanded mining activities that could drive this species to extinction in a short period of time, we assign this species a conservation assessment of Endangered [EN B2ab(iii)].

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.

Additional specimens examined: ― BRAZIL. Pará: Canaã dos Carajás, S11D, vegetação rupestre sobre canga,

6°23’41”S, 50°19’11”W, 26 January 2012, A. J. Arruda , L. V. Costa , M. O. Pivari , T. J. Battituci, F. A de Paula, M. L. Gontijo & B. D. Ranieri 492 ( BHCB!) ; Parauapebas, Serra Bocaina, 6°18’12”S, 49°53’56”W, 8 March 2012, A. J. Arruda , L. V. C. Costa & N. F. O. Mota 642 ( BHCB!) ; Parauapebas , Mirante do Granito , 6°17’02”S, 50°20’13”W, 580 m, 22 March 2012, A. J. Arruda , P. L. Viana , F. M. Santos , P. B. Meyer, P. J. Battituci 780 ( BHCB!, NY!) ; Parauapebas, N-6, campo graminoso sobre canga, 6°07’50”S, 50°10’27”W, 25 March 2012, A. J. Arruda , P. L. Viana , F. M. Santos , P. B. Meyer , P. J. Battituci & L. J. Arruda 845 ( BHCB!) ; Parauapebas, N-6, 6°07’50”S, 50°10’27”W, 697 m, 25 March 2012, A. J. Arruda , P. L. Viana , F. M. Santos , P. B. Meyer , P. J. Battituci & L. J. Arruda 861 ( BHCB!, NY!) ; Parauapebas, N-3, 6°02’30”S, 50°12’28”W, 694 m, 27 March 2012, A. J. Arruda , P. L. Viana , F. M. Santos , P. B. Meyer , P. J. Battituci & L. J. Arruda 902 ( BHCB!, NY!) ; Parauapebas, N-2, 6°03’25”S, 50°14’48”W, 724 m, 19 April 2012, A. J. Arruda , F. M. Santos , L. J. Arruda & T. J. Battituci 952 ( BHCB!, NY!) ; Canaã dos Carajás, FLONA de Carajás, Lagoa do Amendoim , Serra Sul, 6°23’44”S, 50°22’17”W, 12 April 2015, L. M. M. Carreira , T. Guimarães , A. Dias , T. Rodrigues, C. Maurity & D. da Silva 3350 ( MG!) ; Canaã dos Carajás, FLONA de Carajás, rampa que dá acesso a lagoa Três Irmãs, Serra Sul, 6°20’58”S, 50°26’57”W, 17 April 2015, L. M. M. Carreira , T. Guimarães , A. Dias , T. Rodrigues, C. Maurity & D. da Silva 3406 ( MG!) ; Canaã dos Carajás, FLONA de Carajás, encosta de pedras que margeia a lagoa Três Irmãs, Serra Sul, 6°21’09”S, 50°26’54”W, 20 April 2015, L. M. M. Carreira , T. Guimarães , A. Dias , T. Rodrigues, C. Maurity & D. da Silva 3448 ( MG!) ; Parauapebas (Marabá), escassa camada de humus, 6°00’S, 50°18’W, 700 m, 21 May 1969, P. B. Cavalcante 2091 ( MG!) ; Parauapebas (Marabá), Serra dos Carajás, Platô, rocha de minério de ferro, 6°00’S, 50°18’W, 700 m, 21 May 1969, P. B. Cavalcante 2100 ( MG!) ; Parauapebas (Marabá), Norte, 18 April 1970, P. B. Cavalcante & M. Silva 2620 ( MG!) ; Parauapebas (Marabá), nas fendas e furos do lagedo, N1 , 20 April 1970, P. B. Cavalcante & M. Silva 2670 ( MG!) ; Parauapebas , Serra dos Carajás, N5 , without date, P. P. Chaves, L. C. B. Lobato & P. Melo 23 ( MG!) ; Parauapebas, Floresta Nacional dos Carajás, Serra Norte, N1 , 6°02’08”S, 50°16’26”W, 750 m, 11 March 2009, V. T. Giorni , P. L. Viana, L. V. C. Silva, D. F. Silva 83 ( BHCB!) ; Canaã dos Carajás, Floresta Nacional dos Carajás, Serra do Tarzan , 6°20’16”S, 50°09’06”W, 750 M, 14 March 2009, V. T. Giorni , P. L. Viana , L. M. Versieux , L. C. Garcia , L. V. C. Silva & T. S. Silva 145 ( BHCB!) ; Canaã dos Carajás, Floresta Nacional dos Carajás, Serra Sul, 6°23’01”S, 50°23’10”W, 753 m, 16 March 2009, V. T. Giorni , P. L. Viana , L. M. Versieux , L. C. Garcia , L. V. C. Silva & D. S. Silva 179 ( BHCB!) ; Canaã do Carajás FLONA de Carajás. Serra Sul / S11 D Lagoa do Amendoim , 6 o 23’54”S, 50 o 22’19”W, 1 December 2015, R. Goldenberg 2229, P. L. Viana , N. Mota , A. Salino , A. Gil, A. Giulietti-Harley ( UPCB) ; Parauapebas, Serra dos Carajás, Platô N4 , 8 January 2010, L. C. B. Lobato , L. V. Ferreira & P. Prestes 3764 ( MG!) ; Parauapebas, Platô N4 , 6°05’23”S, 50°11’33”W, 13 March 2015, L. C. B. Lobato , F. Peixoto , L. V. Ferreira & A. Rodrigues 4311 ( MG!) ; Canaã dos Carajás, Ao longo da Estrada S11 até S11 A, 6°22’17”S, 50°23’04”W, 22 March 2015, L. C. B. Lobato , F. Peixoto , L. V. Ferreira & A. Rodrigues 4373 ( MG!) ; Canaã dos Carajás, S11 D, margem de lagoa Natural, 6°24” S, 50°21’01”W, 20 March 2012, P. B. Meyer , A. J. Arruda , P. L. Viana , F. M. Santos , T. J. Battituci & L. J. Arruda 1133 ( BHCB!) ; Parauapebas, N8 , campo rupestre sobre canga entremeado campos graminosos e brejos, 6°11’08”S, 50°07’56”W, 23 March 2012, P. B. Meyer , A. J. Arruda , P. L. Viana , F. M. Santos , T. J. Battituci & L. J. Arruda 1177 ( BHCB!) ; Parauapebas, N1 , campo rupestre sobre canga couraçada, 6°01’52”S, 50°17’25”W, 26 March 2012, P. B. Meyer , A. J. Arruda , P. L. Viana , F. M. Santos , T. J. Battituci & L. J. Arruda 1237 ( BHCB!) ; Canaã dos Carajás, S11 A, 6°20’59”S, 50°26’52”W, 9 December 2007, N. F. O. Mota , P. L. Viana , L. V. C. Silva & L. C. Garcia , G. M. Maciel & D. F. Silva 1138 ( BHCB!) ; Parauapebas, FLONA de Carajás, Serra dos Carajás, nos limites da Mina de N5 , 6°01’26”S, 50°07’49”W, 715 m, 27 April 2015, N. F. O. Mota , P. L. Viana , A. Gil , A. L. Ilkiu-Borges & C. S. Nunes 2936 ( MG!) ; Canaã dos Carajás, FLONA de Carajás, Serra dos Carajás, trilha da Lagoa do Amendoim , S11 D, 6°13’01”S, 50°21’25”W, 728 m, 29 April 2015, N. F. O. Mota , P. L. Viana , A. Gil , A. L. Ilkiu-Borges & C. S. Nunes 2981 ( MG!) ; Parauapebas, FLONA de Carajás, Serra dos Carajás, trilha da Lagoa da Mata , entrada da Mina N5 , 6°02’26”S, 50°05’18”W, 674 m, 30 April 2015, N. F. O. Mota , P. L. Viana , A. Gil , A. L. Ilkiu-Borges & C. S. Nunes 2991 ( MG!) ; Parauapebas (Marabá), Serra dos Carajás, jasida de ferro do N- 4, morro da planta pilôto, 750 m, 15 May 1983, N. A. Rosa, M.F.F. da Silva, R.P. Bahia , & J. C. Santos 4607 ( US!) ; Parauapebas (Marabá), Serra dos Carajás, N7 , 4 February 1985, O. C. Nascimento & R. P. Bahia 1138 ( MG!) ; Canaã dos Carajás, Platô S11 D, 6°24’00”S, 50°18’56”W, 20 May 2014, R. S. Santos , P. G. C. Lima , L. C. B. Lobato & M. R. Coelho- Ferreira 213 ( MG!) ; Parauapebas (Marabá), Serra dos Carajás, N-5, 14 May 1982, R. S. Secco , C. R. Sperling , M. Condon, A. Mesquita 159 ( MG!, MO!) ; Parauapebas (Marabá). Corredeira de água sobre pedras, vegetação de canga aberta, 19 March 1985, R. S. Secco , O. M. Barth & M. R. Santos 509 ( MG!) ; Parauapebas (Marabá), Serra dos Carajás, N-4, mina pilôto para exploração de ferro, 700–750 m, 14 March 1984, A. S. L. da Silva, N. A. Rosa , R. P. Bahia , & M. R. Santos 1760 ( MG!, NY!, US!) ; Canaã dos Carajás, S11 D, 6°23’33”S, 50°22’05”W, 24 January 2012, L. V. C. Silva , A. J. Arruda , M. O. Pivari , T. B. Jorge , L. F. A. de Paula, M. Gontijo & B. Ranieri 1076 ( BHCB!) ; Canaã dos Carajás, Serra do Tarzan , 6°19’30”S, 50°07’11”W, 760 m, 9 February 2012, L. V. C. Silva , A. J. Arruda , L. F. A. de Paula, M. Gontijo , A. Salino, T. Alves 1205 ( BHCB!, MG!, NY! [2]) ; Parauapebas (Marabá), Serra dos Carajás, N-4, 25 March 1977, M. G. Silva & R. Bahia 2921 ( MG!-pro parte, MO!, NY!, P-pro parte) ; Serra dos Carajás, 2 km W of AMZA camp N- 5, ca. 700 m, 13 May 1982, 6°04’S, 50° 08’W, C. R. Sperling , R. S. Secco , M. Condon , A. L. Mesquita , B. G. S. Ribeiro, & L. R. Marinho 5619 ( F!, NY!, US! [2]) ; Canaã dos Carajás, S11 D, 6°23’17”S, 50°20’57”W, 7 December 2007, P. L. Viana , L. V. C. Silva , L. C. Garcia , N. F. O. Mota , G. M. Maciel & D. F. Silva 3359 ( BHCB!) ; Canaã dos Carajás, S11 A, 6°18’57”S, 50°26’43”W, 737 m, 21 March 2012, P. L. Viana , F. S. Marino , A. J. Arruda , T. B. Jorge, P. M. Burkowski 5258 ( BHCB!, NY!) ; Canaã dos Carajás, S11 A, 6°20’48”S, 50°25’57”W, 711 m, 21 March 2012, P. L. Viana , F. S. Marino , A. J. Arruda , T. B. Jorge, P. M. Burkowski 5261 ( BHCB!, NY! [2]) ; Parauapebas, FLONA de Carajás, Serra dos Carajás, N1 , 6°02’03”S, 50°16’14”W, 705 m, 26 March 2015, P. L. Viana , A. M. Giulietti , R. M. Harley , A. Cardoso & A. P. O. Cruz 5564 ( MG!) ; São Félix do Xingu , Serra de Campos , 6°32’34”S, 51°52’40”W, 660 m, 01 May 2016, P. L. Viana , A. M. Giulietti , M. T. Watanabe, C. W. Maurity 6132 ( MG!) ; Ourilândia, Serra Arqueada, 6°30’33”S, 51°09’23”W, 633 m, 03 May 2016, P. L. Viana , A. M. Giulietti , M. T. Watanabe, C. W. Maurity 6213 ( MG!) ; Curionópolis, Serra do Cristalino , 6°27’12”S, 49°40’32”W, 760 m, 04 May 2016, P. L. Viana , A. M. Giulietti , M. T. Watanabe, C. W. Maurity 6220 ( MG!) .

Discussion: ―The suite of diagnostic morphological characters that provides a strong rationale for recognizing Brasilianthus as a new genus include its annual habit; haplostemonous, 4-merous flowers; tubulose-subcylindric hypanthium 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, erect ± deltoid appendages; absence of placental intrusions in mature capsules; and subcochleate seeds with a prominently costate testa ( Figures 2–3 , 4 A–C ). This combination of characters is not found among any of the 12 genera currently assigned to the Marcetia alliance, the grouping to which Brasilianthus clearly belongs based on morphological and molecular data. The Marcetia alliance has recently been characterized by its 4-merous flowers, number of ovary locules equal to the number of petals (4 or reduced to 2–3 locules), absence of trichomes on the ovary apex, and seeds that are cochleate, ovate, or lacrimiform ( Michelangeli et al. 2013; Rocha et al. 2016). All of these characters are consistent with Brasilianthus .

The annual habit of Brasilianthus is also notable, but this abbreviated life cycle has evolved in several neotropical genera of Melastomataceae that grow in disturbed or seasonally water-stressed savanna or rocky environments ( Wurdack 1963; Almeda & Robinson 2011).

Haplostemony (flowers with petals and stamens that are equal in number), which is clearly a derived character state in the family, is rare among Melastomataceae generally. For genera of the Marcetia alliance it is a consistent character state for only five of the 15 species of Siphanthera ( Almeda & Robinson 2011) . Among other capsular-fruited neotropical Melastomataceae it is a characteristic feature of the Cyphostyleae ( Michelangeli et al. 2011, 2014), one species of Cambessedesia ( Candolle 1828: 110) , one species of Monochaetum ( Candolle 1828: 138) Naudin (1845: 48–49) , one species of Poteranthera ( Bongard 1838: 137) , and one species of Pterolepis ( Candolle 1828: 140) ( Martins 1984; Alvear 2010; Kriebel 2012; Almeda & Martins 2015). In the Cyphostyleae , the capsular fruits are derived from inferior ovaries. Brasilianthus is like all the other haplostemonous taxa mentioned above in having capsular fruits derived from superior ovaries.

The short cupulate-campanulate anther thecae ( Figures 2E , 3G ) of Brasilianthus are unique and not known to us in any other neotropical capsular-fruited genus of Melastomataceae . When we first examined specimens with good open flowers we suspected that the anthers had been chewed by pollen-robbing insects but examination of additional specimens, dissections of mature flower buds, and field observations confirmed that this unusual anther morphology is natural and not the result of insect-induced damage. The short anther with a wide-rimmed pore is reminiscent of anthers that have been damaged by the dystrophic feeding behavior of Trigona ( Apidae : Meliponinae ) bees that typically perforate and ultimately sever anthers close to their base in search of pollen ( Almeda 1977; Renner 1983). According to Roubik (1989), tropical bees that damage flowers to collect pollen are exclusively meliponines that seek out anthers of nectarless buzz-pollinated flowers visited only by bees. Since the flowers of Brasilianthus are nectarless, it is possible that its anther morphology may provide a visual cue that mimics a ravaged anther and thus deceives and discourages dystrophic feeding by Trigona bees.

Nothing is known about the pollinator spectrum of Brasilianthus or whether the species is self-compatible. The short anthers with wide pores do not seem to lend themselves to the thoracic vibration by bees (sonication or buzzpollination) that is typical for a majority of species in the family ( Buchmann 1983; Renner 1989; Willmer 2011). If the species is self-compatible, these anthers could also conceivably function as splash cups since flowering is coincident with the rainy season and the receptive stigma ( Figure 3G ) provides a suitably large juxtaposed target for airborne pollen. Field studies are needed to determine exactly how these unusual flowers are pollinated.

Within the Marcetia alliance, Brasilianthus groups with two other monotypic genera, Appendicularia thymifolia and Nepsera aquatica , along with Acanthella sprucei , and some species of Ernestia ( Candolle 1828: 121) to form a well-supported clade informally designated as Nepsera and allies ( Rocha et al. 2016). The relationships within the Marcetia alliance are not altered by the inclusion of Brasilianthus ; our results are identical to those of Rocha et al. (2016) except for the addition of this new taxon.

All of the taxa that group with Brasilianthus differ by their suffrutescent or woody perennial habit (except Appendicularia), diplostemonous 4-merous flowers (vs. haplostemonous), persistent calyx lobes that are widest at the base, slightly to markedly dimorphic linear-subulate stamens, hypanthia that persist and envelop maturing capsules, and unadorned ovary apices. Acanthella , the most divergent entity in this assemblage, is readily separated by its petals that are yellow-orange and flushed at the base with red, short or obsolete pedoconnectives, small and inconspicuous bilobed ventral staminal appendages, and prominently winged seeds borne on prominent placental intrusions. Nepsera is also distinctive by virtue of its 5−7-nerved ovate to ovate-elliptic leaves, terminal laxly branched multiflorous panicle, subulate stamens that are somewhat dimorphic in size with bluntly acute bilobed ventral appendages, 3-locular globose capsules with conspicuous placental intrusions, and cochleate seeds with a foveolate testa of isodiametric cells ( Figures 4F, 4I ). A ppendicularia shares an annual habit and lack of placental intrusions with Brasilianthus . The diplostemonous flowers of Appendicularia have dimorphic stamens. It also has similar prolonged pedoconnectives and ventrally bilobed appendages that are dilated basally but distinctly aristate distally. It also differs conspicuously from Brasilianthus in other features. It has flowers that are borne in subsecund terminal cymes, campanulate hypanthia with oblate calyx lobes, a 3-locular ovary, and cochleate seeds with a foveolate testa of isodiametric cells that have striate microrelief on the periclinal walls ( Figures 4D, 4G ). Ernestia pullei also shares the distinctive staminal morphology of Appendicularia and Brasilianthus but it differs from the latter in being shrubby with 5-nerved ovate to ovate-elliptic leaves, hypanthia that are suburceolate and distinctly constricted distally in fruit, a 3-locular ovary with placental intrusions, and cochleate seeds with a distinctly tuberculate testa reminiscent of Ernestia confertiflora ( Figure 4H ), a closely related species.

It is important to note that no synapomorphy or unique character combination has been found for the Nepsera clade or for the clade recovered here that includes Brasilianthus , Nepsera , Appendicularia, and Ernestia pullei . Given the distinctive anther morphology, the unique combination of characters, and the lack of diagnostic characters or character combinations for the more inclusive clades, we believe that the best solution is to recognize this unusual species as a new monotypic genus.

Among the collections cited here, Silva & Bahia 2921 at MG and P are mixed collections of Brasilianthus carajensis and Cuphea carajasensis Lourteig (1987: 13) , another canga endemic in the Lythraceae with superficially similar narrow leaf blades. The sheets of Silva & Bahia 2921 at MO and NY are entirely Brasilianthus .

Figures

FIGURE 2. Brasilianthus carajensis. A. Habit. B. Cauline leaf (abaxial surface). C. Flower (at anthesis) with subtending leaves. D. Petal. E. Stamen (profile view). F. Dehisced loculicidal capsule showing crown of four deltoid appendages and irregularly rupturing hypanthium. G–H. Seeds. (A−E, G−H drawn from Silva et al. 1760, US; F drawn from Sperling et al. 5619, US).

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. G. Profile view of flower (at anthesis) showing posture of stamens, appendages, style, and stigma. H. Mature hypanthium showing alveolate surface (when fresh) and erect calyx lobes with constricted base. I. Flower (profile view) with subtending leaves. All photographs by P.L.Viana.

FIGURE 4. Scanning electron micrographs of seeds of Brasilianthus, Appendicularia, Nepsera, and Ernestia. A. Brasilianthus carajensis (Viana et al. 5261, NY). B, C. Brasilianthus carajensis (Rosa et al. 4607, US). A. profile view. B. view of raphal zone. C. costate ridges and testa. D, G. Appendicularia thymifolia (Cremers & Hoff 10740, CAS). D. profile view. G. enlarged portion of testa. E. profile view of Ernestia rubra (Maguire 54197, NY). H. profile view of Ernestia confertiflora (Pires 50980, NY). F, I. Nepsera aquatica (Wilbur & Moore 70136, CAS). F. profile view. I. enlarged portion of testa. Scale bars: A = 10 μm, B = 20 μm, C = 10 μm, D = 10 μm, E = 10 μm, F = 20 μm, G = 10 μm, H = 100 μm, I = 10 μm.

FIGURE 5. Geographic distribution of Brasilianthus carajensis with collection localities represented by triangles.