Carajasia cangae R.M. Salas, E.L. Cabral & Dessein, 2015

Salas, Roberto M., Viana, Pedro L., Cabral, Elsa L., Dessein, Steven & Janssens, Steven, 2015, Carajasia (Rubiaceae), a new and endangered genus from Carajás mountain range, Pará, Brazil, Phytotaxa 206 (1), pp. 14-29 : 16-20

Carajasia cangae R.M. Salas, E.L. Cabral & Dessein , gen. et sp. nov.

Carajasia and C. cangae differ from the remaining genera of Spermacoceae in having flowering branches with two axillary flowers each node, homostylous flowers, corolla with a fringe of moniliform hairs, pubescent styles with distinct stigma lobes, 2-lobed nectariferous discs, bireticulate pollen grains, dry fruits with septicidal dehiscence into two caducous mericarps leaving a basal carpophore and each mericarp covered by a hyaline wall of the intercarpelar septum.

Type:— Brazil: Pará: Canaã dos Carajás, Flona de Carajás, Serra Sul, S 11- C, 6°22’19”S, 50°23’5”W, 723 m, 22 March 2012, Viana P. L., Santos F. M, Arruda A. J., Jorge T. B. & P. M. Burkwoski 5263 (holotype BHCB, isotype CTES, MG). ( Figs. 1–7 )

Herbs 2–10 cm tall, perennial, with main branches erect. Stem tetragonal, glabrous, papillate on angles, wine-colored. Stipules fimbriate, basal sheath 0.1–0.15 mm long, glabrous or with a few scattered short and triangular hairs, with 6–7 fimbriae; fimbriae 0.1–0.18 mm long, glabrous, with apex glandular. Leaves pseudoverticillate (due to the presence of axillary brachyblasts), sessile; blades narrowly ovate, 1.8–2.1 x 0.5–0.7 mm, attenuate at the base, acuminate at the apex, slightly succulent, glabrous; primary veins visible on the adaxial side; secondary veins 3–4 on each side of the main vein, alternate and visible on abaxial side. Flowering branches with two axillary flowers on each node; each flower subtended by 2 foliaceous bracts; bracteoles inconspicuous. Flowers sessile, homostylous; hypanthium obovoid, pubescent; calyx tube 0.05 mm long; calyx 4–lobed, lobes triangular, 0.15–0.17 mm long, margin ciliate; corolla 1–1.2 mm long, tube funnel-shaped, equal or slightly shorter than the corolla lobes, internally with a fringe of moniliform hairs from the base of the stamens to near the base of the tube, externally pubescent, lobes internally glabrous; stamens shorter than the corolla lobes, anthers 0.45–0.48 mm long, pollen 5–7 colporate, bireticulate, spheroidal, E 20.6–21 μm, P 19–21 μm, ectocolpi 12–12.7 μm long, endoaperture an endocingulum, infrareticulum complete, muri spinose, suprareticulum reduced, muri mostly psilate ( Fig. 2 H–J ); style 1.1–1.2 mm long; nectariferous disc 2-lobed, with certain triangular papillae taller than the remaining cells of the disc, each papilla with striated cuticle; ovary 2-locular, obovate, placenta attached near the middle of the septum, each locule 1-ovulate. Dry fruit obovoid, 0.9–1.1 mm long, pubescent, with septicidal dehiscence into two caducous mericarps leaving a basal carpophore, each mericarp covered by a hyaline wall of the intercarpelar septum; seeds plano-convex, ovate in outline, wing absent, 0.7–0.75 mm long; ventral face slightly furrowed, partially covered by the strophiole, with numerous raphides; testa reticulo-areolate.

Etymology: —The genus is named after “Floresta Nacional de Carajás”, especially to the Carajás mountain range, Pará, Brazil, the only region where the plant was found. The specific epithet refers to Canga vegetation, which is the only habitat in which the species was found ( Fig. 5 ).

Distribution and habitat: —All collections of this species are from the municipality of Canaã dos Carajás, state of Pará, Brazil. They inhabit ferric soil (or Canga) only on the top of the Carajás mountain range ( Fig. 3 , 4 ). These mountains are situated at 580–850 m elevation and surrounded by Amazonian forest at lower elevations.

Conservation Status: — Carajasia cangae should be classified as endangered [EN B2ab(ii, iv)] according to IUCN Red List criteria (IUCN 2001): area of occupancy estimated to be less than 50 km 2 in a severely fragmented area, besides the species is only known from fourteen collections, all from one location. Planned mining activities form the main threat to the species.

Conservation of habitat in the future: —The Serra do Carajás is located in the southeastern portion of Pará State in northern Brazil. It is an isolated mountain range in the eastern Amazon region. The rugged relief of the region bears a rich mosaic of vegetation types and consists of one of the most important forest remnants in the eastern Amazon. It is partially situated within the limits of a conservation unit, the FLONA Carajás (Carajás National Forest). The diversity of endemic species of the canga from the Serra do Carajás region is noteworthy. Although the flora is still not satisfactorily inventoried, several endemic plant species are known from the canga vegetation of this region ( Secco & Mesquita 1983, Morelato & Rosa 1991).

The distribution of Carajasia cangae coincides with the extension of the Serra Sul mountain, which covers an area of approximately 50 km 2 located within a single municipality. For organizational purposes this mountain used to be divided in four different areas, known as S11-A, S11-B, S11-C and S11-D ( Golder Associates Brasil 2009). This region harbors one of the most important iron deposits in the world and is part of the Carajás Mineral Province ( Lindenmayer et al. 2001). The vegetation on the top of Serra Sul is composed of patches of saxicolous scrubby vegetation, which occur on the iron outcrops, and is commonly referred to as “canga” ( Secco & Mesquita 1983). In this area, C. cangae occurs as small populations distributed along storm drains on consolidated iron outcrops. One of the areas mentioned above, S11-D, will become in 2016 one of the largest open-pit mine of the world ( Golder Associates Brasil 2010). Despite many efforts during the period 2010–2012 looking for populations of C. cangae in localities outside Serra Sul, no other localities were found. Half of the known collections of C. cangae came from “area S11-D” of Serra Sul. For this reason, conservation efforts for this monotypic genus are highly needed to ensure its survival. In a first phase, seeds need to be collected and conserved in a seed bank for ex-situ conservation. Ideally, this would be combined with cultivating the plant in botanical gardens worldwide. In parallel, the natural populations should be monitored, and the influence of the mining activities evaluated, which would support the development of effective strategies to insure the survival of this taxon in the wild.

Additional specimens examined (paratypes):— BRAZIL: Pará: Canaã dos Carajás, Flona de Carajás, Serra Sul, S11-A, drenagem em meio a vegetação rupestre sobre canga, 6°17’30,54”S, 50°28’8,19”W, 710 m, 21 July 2012, Arruda A.J,. Paula L.F.A., Silva L.V.C. & Jorge T.B. 1199 (BHCB); S11-B, vegetação rupestre, 6°20’36”S, 50°25’25”W, 747 m, 27 January 2012, Silva L.V.C., Pivari M.O., Jorge T.B. & Gontijo M. 1127 (BHCB); S11-B, vegetação rupestre, 6°20’32”S, 50°25’4”W, 724 m, 25 April 2012, Arruda A.J., Santos F.M., Arruda L.J. & Jorge T.B. 1094 (BHCB); S11- C, vegetação rupestre, 6°22’23”S, 50°23’24”W, 700 m, 24 January 2012, Silva L.V.C., Arruda A.J., Pivari M.O., Jorge T.B., Paula L.F.A., Gontijo M. & Ranieri B.D. 1081 (BHCB); S11-C, campo graminoso associado a drenagem com muitas pedras, 6°22’22”S, 50°23’03”W, 723 m, 20 March 2012, Arruda A.J., Viana P.L., Santos F.M., Burkowski P.M., Jorge T.B. & Arruda L.J. 737 (BHCB); S11-D, vegetação rupestre sobre canga, 6°24’28”S, 50°21’5”W, 819 m, 24April 2012 (small population, less than 30 individuals), Arruda A.J., Santos F.M., Arruda L.J. & Jorge T.B. 1085 (BHCB); S11-D, mata baixa sobre canga, 6°23’31”S, 50°19’9”W, 604 m, 23 May 2012, Arruda A.J. Salino A. & Arruda L.J. 1172 (BHCB); S11-D, campo graminoso alagado sobre canga, 6°24’5”S, 50°21’33”W, 797 m, 24 April 2012, Arruda A.J. Santos F.M., Arruda L.J. & Jorge T.B. 1078 (BHCB); S11-D, mata baixa, 6°24’25.26”S, 50°18’55.02”O ”W, 720 m, 1 July 2010, Almeida T.E., Marino F., Megale M. & Arruda , A.J. 2463 (BHCB); S11-D, vegetação rupestre, 820 m, 18 May 2010, Pivari M.O., Silva L.V.C. & Santos A.O. 1504 (BHCB); S11-D, 6°23´08”S, 50°23´05”W, 16 April 2009, Giorni V.T., Viana P.L., Versieux L.M., Garcia L.C., Silva L.V.C. & Silva , D.S. 173 (BHCB); S11-D, vegetação rupestre, 753 m, 11 October 2008, Silva L.V.C. 558 (BHCB); Serra Sul, ocorre em córregos sobre canga, lajeado, nas rochas que permanecem secas, 22 March 2012, 6°17’02”S, 50°20’13”W, 580 m, Burkowski P.M., Arruda A.J., Viana P.L., Santos F.M., Jorge, T.B. & Arruda L.J. 1152 (BHCB, CTES); vegetação de canga, 16 April 1986, Secco R.S., Silva M.F.F., Carreira L. & Salomão R.P. 714 (MG); 28 May 1987, Silva M.F.F. & N.A. Rosa 2455 (MG).

Taxonomic notes:— The dehiscence of the Carajasia fruits is most similar to some species of Crusea ; in both genera the dehiscence is septicidal and separates the fruit into two caducous mericarps leaving a basal carpophore on the pedicel. The ventral face of each mericarp is covered by a hyaline wall that belongs to the intercarpelar septum, which in Fig. 1 I–L was removed to shows the seed and in the Fig. 2 F remains complete.

Besides Carajasia , there are eleven supraspecific taxa known within the Spermacoce clade that are characterized by deeply divided stigmas [ Borreria subsect. Latifoliae ( Schumann 1888: 143) , Bacigalupo & Cabral 1996: 306), Diodia , Emmeorhiza , Galianthe , Mitracarpus , Psyllocarpus sect. Amazonica Kirkbride (1979: 13) , Richardia , Schwendenera , Staelia , Tobagoa and Tortuella ]. An artificial key to distinguish Carajasia from the remaining taxa with deeply divided stigmas is presented below.

Figures

FIGURE 1. Carajasia cangae. A, habit, in rectangle a diagram of flowering branch; B, stipule with fimbriate edge. C, abaxial face of leaf; D, transversal section of leaf; E–H, flower; E, flower with a creased corolla lobe; F, hypanthium, style and stigma; G, inside of corolla; H, style and stigma; I–L, fruit; I, dehiscent fruit; J, ventral view of mericarps without a hyaline intercarpelar septum; K, dorsal view of mericarps; L, transversal section of mericarps; M, seed. Drawn by Laura Simón from the holotype [Viana et al. 5263 (BHCB)].

FIGURE 2. Microphotographs from the scanning microscope of Carajasia cangae. A, stipule; B, leaf; C, immature fruit; D, apical view of fruit; E, lateral view of mericarp with the septum at the base; F, internal view of mericarp; G, inside view of anther locule without orbicules; H–J, bireticulate pollen grains; H, polar view; I, ecuatorial view; J, exine. A–J, from holotype [Viana et al. 5263 (BHCB)].

FIGURE 3. Images of Carajasia cangae. A, Carajasia cangae and Paepalanthus fasciculoides Hensold growing on the Canga soil; B, habit of well-developed plant; C, reduced habit; D, detail of the inflorescence; E, apex of the inflorescence; F, flowers, flowers bud and immature fruit, the arrow indicating the papillae over the fruit. Scale bars: C: 1 cm, D, E and F 1 mm. Photographs by P.L. Viana.

FIGURE 4. Image of Canga vegetation, the natural environment of Carajasia cangae. A, temporary streams with xerophytic vegetation, with some caespitose grasses, the Philodendron wullschlaegelii Schott and some scattered ferruginous plants of C. cangae. B, C, some plants of different stature of C. cangae. Photographs by P.L. Viana.

FIGURE 5. Geographic distribution of Carajasia cangae with collections represented by stars.

FIGURE 6. Phylogenetic tree showing the relationship of Carajasia with the remaining genera of Spermacoce clade.

FIGURE 7. Comparison between phylogenetic results with pollinic and morphologic data. The same tree of the figure 7 with the replacement of the terminals by its taxonomic equivalent (genera or infrageneric taxa) or informal groups (as Diodella teres group).