Metrodorea concinna Pirani & P.Dias, 2013

Dias, Pedro, Udulutsch, Renata Giassi & Pirani, José Rubens, 2013, A new species of Metrodorea (Rutaceae) from Brazil: morphology, molecular phylogenetics, and distribution, Phytotaxa 117 (2), pp. 35-41 : 37-39

Metrodorea concinna Pirani & P.Dias , sp. nov. ( Figure 2 )

Ab omnibus aliis speciebus generis ramis furcatis, foliis parvis glaberrimis plerumque unifoliolatis rarissime 2–3- foliolatis, subsessilibus, inflorescentiis brevis, capsulis rugulosis pauce tuberculatis differt.

Type:— BRAZIL. Bahia: Lençóis, Remanso , Maribus , Rio Santo Antônio , elevation 380 m, 12° 39’ S, 41° 19’ W, 29 January 1997 (fl), S . Atkins , E . Saar , L . Passos , L . Funch , M . L . Guedes & B . Stannard PCD-4655 (holotype SPF!, isotypes ALCB!, CEPEC!, HUEFS!, K!, NY!) .

Shrub or small tree 1–4 m tall, trunk ca. 15 cm diam.; branchlets deflexed, grayish-green to brownish, shiny, glabrous, with sparse, pale lenticels. Leaves opposite, 1(–3)-foliolate, the leaflets sessile; sheath to 4 mm long, at apex cucullate, rounded, sometimes ciliate or ciliolate, on abaxial surface glabrous, on adaxial surface pubescent with brown, multicellular trichomes, later on reflexing and becoming glabrous, falling off with the leaves; petiole seemingly absent or up to 7 mm long, adnate to the abaxial side of the sheath, semiterete and canaliculate, sparsely and minutely puberulous to glabrous; leaflet blade narrowly elliptic (or that of the terminal leaflet of the occasional 3-foliolate leaves obovate), often slightly asymmetric, 1.8–5.5 × 0.9–2.7 cm (those of young vegetative shoots to 6.5 × 3.1 cm), rounded to minutely auriculate or sometimes shortly attenuate and usually unequal at base, attenuate to rounded or retuse, seldom acute at apex, (sub)revolute, chartaceous, glabrous, olive-green and dull on both surfaces, the abaxial surface paler; venation brochidodromous, prominent on both sides, more so beneath. Inflorescence a narrow simple thyrsoid, sometimes a diplothyrsoid, terminal or axillary near tips of branchlets, sometimes emerging from leafless axils below the distal portion of a branch, erect to curved, usually longer than leaves, (0.8–)2–5× 1–3.5 cm, densely pubescent with minute, erect trichomes, glabrescent; side-branchlets opposite, 0.4–3.5 cm long, patent, the lowermost ones usually inserted at base of inflorescence which is then virtually sessile; peduncle 0–7 mm long; bracts deltoid, ca. 1 mm long, minutely pubescent; pedicels 1.4–2 mm long, minutely pubescent to glabrous; bractlets (prophylls) 2 per flower, opposite, ca. 0.7 mm long, deltoid, minutely pubescent, usually subtending secondary pedicels or floral buds. Flowers pentamerous, 5–6 mm in diam.; calyx lobes 5, subvalvate, connate at base up to half the length, depressedly ovate, ca. 0.5 mm long, slightly acuminate at apex, subcoriaceous, glandular, chartaceous, reddish to purple, glabrous at adaxial surface, glabrous to sometimes minutely puberulent at abaxial surface, ciliolate; petals 5, valvate, widely spreading at anthesis but later reflexed and finally deciduous, oblong-elliptic, 3.0–3.2 × 1.3–1.5 mm, acute at apex, induplicate at margin, shortly unguiculate at base, coriaceous, claret or dark purplish when living, brownish to red-purplish (dark purplish when in bud) when dried, glandular, glabrous, the venation cladodromous (of subparallel, fewbranched veins); filaments 5, alternate with the petals, subulate, 1–1.4 mm long, glabrous, acuminate at tip, purplish, reflexed after anthesis, persistent; anthers heart-shaped, ca. 0.8 mm long including the small mucronate tip, glabrous, yellow, early deciduous; disc annular, adnate to the ovary in the lower half, 5-lobed, slightly undulate at each lobe, ca. 2 mm in diam., fleshy, provided with some glandular tubercles up to 0.1 mm long, glabrous; carpels 5, adnate to the disc and connate proximally, ca. 1 mm high, on a raised receptacle, barely protruding beyond the disc, provided with many glandular, terete tubercles 0.1–0.3 mm long, glabrous; ovules 2 per carpel, collateral, pendulous; style terete or slightly obtuse-angled, inserted proximally between the carpels, projecting beyond them up to 0.5 mm, reddish, glabrous; stigma capitate, slightly 5-lobed, light green. Fruit a depressed, stellately 5-lobed capsule, 1.3–1.8 × 2.2–2.5 mm when dehisced, glandular, glabrous, transversely wrinkled with prominent (sub)parallel veins at exocarp and mesocarp, with few, sparse, obtuse, small tubercles, each carpel with a dorsal, blunt, 1–3 mm long apophysis, dehiscent septicidally along the dorsal commissures from apex to 1–2 mm above the base, and loculicidally from the base along the ventral sutures to the dorsal apophysis; endocarp smooth, ochre-yellow, hard, when drying ruptured from the rest of the pericarp and expelling the seeds, later deciduous. Seeds 1–2 per locule, ovoid, ca. 3–5 mm long, obtuse at apex, truncate at base, the testa coriaceous, dark-gray to brownish, dull, slightly ridged; chalazal area dark brown-black, shiny; hilum thin; embryo not seen.

IUCN conservation assessment:— The inferred extent of occurrence of Metrodorea concinna is ca. 45,000 km 2, although its area of occupancy seems to be less than 1% of that extent. The five collections of this species have been collected from only three different sites [two pairs of them are sufficiently close so that they are superposed on the map ( Figure 1 )]. According to the guidelines of the IUCN Standards and Petitions Subcommittee (2011), this species can be assigned to the Endangered risk category [ EN, B 2a, b(ii,iii), and D], because of its small area of occupancy and because very few individuals are known from only three different sites, one of which is subject to strong human pressure.

Etymology:—The epithet concinna is derived from the Latin term concinnus, which means “pretty,” “neat,” “elegant,” referring to its habit and leaf arrangement.

Additional specimens examined (paratypes):— BRAZIL. Bahia: Andaraí, km 40 de la route de Itaeté a Andaraí, vers Le Rio Paraguaçu, 26 November 1986 (fl), P . A . Loizeau et al. 512 ( CEPEC). Ibiquera, ca. 20 km a leste do entroncamento para Lençóis na rodovia BR- 242, 470 m, 12° 30’ 27” S, 41° 11’ 5” W, 12 July 2003 (fl), F . França et al. 4778 ( HUEFS, SPF). Lençóis, BR-242, sentido Lençóis – Itaberaba, a 20,8 km após o entroncamento para Lençóis (ou 135 km do entroncamento para Andaraí), 12° 30’ 26,9” S, 41° 11’ 05,6” W, 461 m, 6 February 2007 (st), P . Dias & R . G . Udulutsch 318 ( PA, SPF). Ubiraitá, 12° 34’ S, 41° 07’ W, 23 June 1978 (fr), J . E .M. Brazão 61 ( RB) .

Morphology, molecular phylogenetics, and distribution:— Metrodorea concinna is morphologically similar to the sympatric M. mollis (see Table 1 for detailed comparison), in the general aspect by its shrubby to treelet habit ( Figure 3A ) with relatively small leaves ( Figure 2A ) with sessile leaflets ( Figure 2C and D , and Figure 3C ), which are two of the characters shared by both species. But the new species is easily differentiated from its congener by the regularly ramified (mostly bifurcate) young shoots ( Figure 2A , vs. irregularly ramified shoots in M. mollis ), the usually sessile leaves (petiole absent or seldom up to 7 mm long vs. 2–12 mm long in M. mollis , Figure 3B ), which are predominantly 1(–2)-foliolate on flowering branches ( Figure 2A , vs. 3-foliolate in M. mollis ), by the leaflets, which are not conspicuously dotted with dark glands ( Figure 3E and F ), and by the inflorescence that is shorter than the leaves ( Figure 2A , vs. longer than the leaves in M. mollis ). Besides, the fruit has prominent dorsal apophyses, one per carpel ( Figure 2I , vs. fruit without apophyses in M. mollis ), and wrinkled surface provided with only a few tubercules ( Figure 2I and Figure 3D , vs. fruit muricate-tuberculate in M. mollis ). Metrodorea concinna is also sympatric with M. nigra and M. maracasana , although neither of them is involved in sister-group relationship to any other individual species. Metrodorea concinna is easily differentiated from M. maracasana by its shrubby to treelet habit ( Figure 3A , vs. arboreous habit in M. maracasana ), its sessile leaflets ( Figures 2C, 2D and 3C , vs. petiolulate leaflets in M. maracasana ), and its fruits with dispersed tubercules ( Figures 2I and 3D , vs. fruits with crowded tubercules in M. maracasana ); and from M. nigra by its shrubby to treelet habit (vs. arboreous in M. nigra ) and sessile leaflets (vs. petiolulate leaflets in M. nigra ).

According to the phylogeny of Metrodorea proposed by Dias et al. (submitted), and shown on Figure 3 , phylogenetic relationships in Metrodorea are as follows: M. stipularis , endemic to the Parana Forest Province, is sister to all other species of the genus. The second split separated M. nigra , which occurs in both the Parana Forest and Brazilian Atlantic Forest, from the clade ( M. maracasana ,( M. concinna ,( M. mollis , M. flavida ))). Thirdly, M. maracasana , which is also endemic to the Parana Forest, separated from (i.e., is sister to) the other three species of the genus: M. concinna , M. flavida , and M. mollis . Metrodorea concinna is sister to the crown clade comprised by M. mollis and M. flavida . Metrodorea concinna is endemic to southeastern part of Bahia state (eastern Brazil), whereas M. flavida is confined to the Amazon region (northern Brazil). Metrodorea mollis , in turn, is sympatric with M. concinna (endopatric, according to Papavero et al. 1994, Figure 1 ), however, in a narrower geographical scale, M. concinna occurs isolatedly from all other species of the genus, as its area of occupancy (even its inferred extent of occurrence) is not shared with any other Metrodorea species ( Figure 1 ).

Figures

FIGURE 1. Geographic distribution of M. concinna and of sympatric species of Metrodorea (the distribution of the entire genus is shown on the largest insert on the upper left corner.) Province names are according to Morrone (2006) with the modifications introduced by Dias et al. (submitted). White areas within Caatinga and Cerrado provinces are “campos rupestres”.

FIGURE 2. Metrodorea concinna. A. Flowering shoot. B. Young shoot with unifoliolate leaves and cucullate sheath protecting the buds. C, D. Trifoliolate leaf with sheath at base, adaxial (C) and abaxial (D) surface. E. Flower after anthesis; note dehisced anthers, the disc and the glandular tubercles which cover the carpel’s dorsal surfaces. F, G. Petal, adaxial (F) and abaxial (G) views. H. Floral axis with bracts and mature flower with petals removed. I. Dehisced capsule, only the dry exocarp and mesocarp remain (except for one carpel). J. Two seeds, note chalazal area and hylum. A–H from Atkins et al. PCD-4655 (type); I–K from Brazão 61.

FIGURE 3. Simplified phylogeny of the genus Metrodorea, modified from Dias et al. (submitted). Key features are optimized on the tree