Mimosa porrecta L. Jordão, M. P. Morim & Baumgratz

Jordão, Lucas Sá Barreto, Morim, Marli Pires & Baumgratz, José Fernando Andrade, 2014, A new species of Mimosa (Leguminosae) from Brazil, Phytotaxa 184 (3), pp. 131-138 : 132-137

Mimosa porrecta L. Jordão, M. P. Morim & Baumgratz ( Figs. 1–6; Tab. 1)

Mimosa porrecta is similar to M. sensitiva L. but differs in having porrect-stellate trichomes on the stems and dendritic trichomes in the fruits.

Type: — BRAZIL. São Paulo: São José do Barreiro, subida para o Parque Nacional da Serra da Bocaina , 12 May 1980 (fl, fr), H . C . Lima & T . P . Ramamoorthy 1218 (holotype: RB!, isotype: HUEFS) .

Scandent shrub; indumentum with puberulous, villose, glandular-subsessile and porrect-stellate trichomes; aculei in series along the striation on the stem, petiole, pinna and sometimes on the peduncle, recurved, dilated and pilose at the base. Stems terete, striate. Stipule 2,5–3,5 x 1–1,7 mm, persistent, lanceolate, margin setose-ciliate, cilia antrorse, adaxial surface puberulous-appressed, abaxial surface with villose, glandular-subsessile and setose-antrorse trichomes, 1–3-nerved, veins inconspicuous. Leaves with 1 pair of pinnae; petiole 25–83 mm long; paraphillidia 1–2,2 mm long., unequal in size, lanceolate; leaflets 2 pairs, 20–70 x 10–39 mm, the innermost of proximal pair reduced, discolour, elliptic to oval, base oblique-obtuse to -cordate, apex acute, margin setose-ciliate, cilia antrorse-appressed, adaxial surface sparsely puberulent, abaxial surface densely with porrect-stellate and glandular-subsessile trichomes; 2–5-nerved, the midrib prominent, the secondaries veins conspicuous and pale on the abaxial surface. Inflorescence axillary, racemose or pseudoracemose, capitate-globose, moriform; peduncule 10–27 mm long; bracteole 1,2–1,5 mm long, oblanceolate, apex acute, margin ciliate-setose to the apex, cilia antrorse, glabrous. Flower tetramerous, isostemonous; calyx 1,5–2 mm long, pappiform; corolla 1,8–2,1 mm long, narrowly tubulose to campanulate, lobes 1- nerved, apex puberulent; filaments pink, free; pollen 7,7(8,9±0,1)–10 μm long., exine ca. 1 μm thick, tetrad tetrahedral, spheroidal, surface areolate; ovary glabrous. Craspedium 13–30 x 5–7 mm, articulate, sessile, oblong, replum densely with dendroid trichomes, epicarp papiraceous, densely with porrect-stellate and villose trichomes. Seed 4–4,5 x 3–3,2 mm, 2–5, obovate, pleurogram apical-basal; plumule differentiated in inflexed eophylls and estipular segments.

Additional specimens examined (paratypes): — BRAZIL Minas Gerais: Caeté, Serra da Piedade , descendo da igreja em direção à base da serra, 10 March 1996 (fl), J. A . Lombardi 1241 ( BHCB, MBM); Carmópolis de Minas , Estação Ecológica da Mata do Cedro , 13 March 2004 (fl), L . Echternacht & T . Dornas 322 ( BHCB, RB); Porteirinha , Cachoeira do Cerrado , 8 June 2010 (fl), A. C . Cervi et al. 9849 ( MBM); São Gonçalo do Rio Abaixo , Estação Ambiental de Peti / CEMIG , 20 June 2002 (fr), J. A . Lombardi & A . Salino 4907 ( BHCB) ; Rio de Janeiro: Barra Mansa, Pombal, Fazenda da Boa Esperança , 8 May 2013 (fl), L. S. B . Jordão 104 ( R, RB); 8 May 2013 (fl, fr), L. S. B . Jordão 105 ( R); 8 May 2013 (fl, fr), L. S. B . Jordão 106 ( R); Petrópolis, Morro do Cuca , 2 June 1984 (fr), H. C . Lima 2154 ( RB); Parque Nacional da Serra dos Órgãos , Fazenda Boa Esperança. área de pasto, na borda da mata, 1 July 2010 (fl), M. J. F . Barros 80 ( RB); Parque Nacional da Serra dos Órgãos , Bonfim , trilha para o Pico do Alcobaça , na beira da estrada de terra que dá acesso à trilha, próximo à pastagem, 5 May 2012 (fl, fr), L. S. B . Jordão 10 ( R); 5 May 2012 (fl), L. S. B . Jordão 11 ( R); 5 May 2012 (fl), L. S. B . Jordão 135 ( R, RB); Correas, Fazenda Bonfim, 1970 (fl), Jesus [?] 313 ( R); Nova Friburgo: s.l., 26 August 1935 (st), L . Xavier 435 ( RBR); Paty do Alferes , 11 November 1935 (fl), H . Monteiro 1253 ( RBR 21163); Teresópolis, à margem da rodovia Teresópolis-Nova Friburgo , 25 August 1935 (fl), H . Monteiro 1253 ( RBR 21164) ; São Paulo: São José do Barreiro, Serra da Bocaina , 2 June 2010 (fl), A. C . Cervi et al. 9540 ( MBM); 6 March 2010 (fl), J . Cordeiro & J. M . Silva 3486 ( MBM, RB); São José dos Campos, s.l., June 1909 (fl, fr), A . Löfgren 165 ( RB) .

Etymology:—The epithet refers to the conspicuous porrect-stellate trichome type prevailing on the stems.

Distribution and habitat: —Endemic to Brazil, and found in the states of Minas Gerais, Rio de Janeiro, and São Paulo, mainly in highlands of the Atlantic Domain and ecotones in the Cerrado Domain, forests and roadsides, and open and pasture areas, between 650–1650 m altitude.

Affinities and notes on critical characters:— Mimosa porrecta is very close to the species of sect. Mimosa ser. Mimosa subser. Mimosa , mainly in having pinnae unijuga with two pairs of leaflets, the innermost of the proximal pair reduced, smaller than the others, and isostemonous flowers, with pink filaments ( Barneby 1991). The recent phylogenetic study of Simon et al. (2011) showed that the species of subser. Mimosa from South America grouped into a well-supported monophyletic clade, with 99% bootstrap. Barneby (1991) also noted that these species form a taxonomic group, sharing this same geographical distribution.

Mimosa sensitiva is distinguished from other South American species by the pappiform calyx ( Barneby 1991), but it shares this characteristic with M. porrecta . Mimosa sensitiva has two varieties: the typical variety and M. sensitiva var. malitiosa Barneby. The varieties are distinguished, respectively, by the shape of the inflorescence (moriform × conelike), the shape and length of the bracteoles (linear-oblanceolate, 0.8–1.5 mm long × spatulate, 2–4 mm long), and the length of the setose trichomes of the bracteole margin (<0.3 mm long × 1–4 mm long).

Mimosa sensitiva var. sensitiva is distributed in Venezuela and widely in Brazil, where it occurs in the Atlantic, Caatinga, and Cerrado domains, from sea level up to 1.000 m altitude. It is found in different habitats including coastal regions, restingas, dry forests and secondary formations, but especially in lowlands and inland formations, such as cerrado and campo rupestre vegetation. Southwestern Bahia and adjacent areas in Minas Gerais state correspond to the southern limit of distribution of this variety and the northern limit of M. sensitiva var. malitiosa , which can be found in disturbed grassland and forests and on roadsides ( Barneby 1991). These two varieties occur allopatrically in relation to the distribution of M. porrecta .

Mimosa porrecta shows tigmonastic movement, similarly to M. sensitiva . Despite the close affinity between the two taxa, mainly in the pappiform calyx, this new species can be distinguished by certain vegetative and reproductive characteristics.

Mimosa porrecta has the indumentum composed of puberules and villose glandular-subsessile trichomes, and two types of branched trichomes, porrect-stellate ( Fig. 4B,C ) and dendritic ( Fig. 4D ), based on Metcalfe & Chalk (1979). The porrect-stellate trichomes densely cover the stems, stipules, petioles, rachis and rachille leaves, abaxial surfaces of the leaflets, and the fruit epicarp. The dendritic trichomes are present only on the replum of the craspedium. In contrast, the two varieties of M. sensitiva have the indumentum with variable density and composed of puberules and villose non-branched trichomes, and glandular-subsessile and setulose trichomes, according to the analysis of several specimens ( Jordão 2014), including the holotype of M. sensitiva var. malitiosa (Martius 1079 K).

(H.C. Lima 2154, RB). Illustrator: Angela S. Rodrigues.

Barneby (1991), based on the ratio between the lengths of the bracteole and flower bud, distinguished two types of capitate inflorescence shape: conelike, with a conical shape due to the imbricate bracteoles being longer than the bud ( Fig. 6A ); and moriform, resembling a mulberry fruit, with the bracteole length equal to or less than the floral bud length, and the bracteoles are not imbricate ( Fig. 6B ). As Mimosa porrecta and M. sensitiva var. malitiosa have moriform inflorescences, some specimens were misidentified as being this variety; however, M. sensitiva var. sensitiva has conelike inflorescences.

Characteristics of the fruit are also significant for taxonomy of Mimosa , as previously noted by Barneby (1991), Dutra (2009) and Simon et al. (2011). The craspedium of M. porrecta differs from other related species in having the epicarp densely covered with porrect-stellate trichomes, and the replum with dendritic trichomes.

IUCN Conservation assessment: — M. porrecta has a scandent shrubby habit. It occurs only in southeastern Brazil, in the states of Minas Gerais, Rio de Janeiro and São Paulo (EOO= 132,653 km ², GeoCAT), in highland areas of the Atlantic Forest and Cerrado domains between 650 and 1640 m altitude. It is common in disturbed sites, open and pasture areas, and forest and roadsides. Although M. porrecta occurs in heavily human-impacted areas, it is also found in several Conservation Units of Rio de Janeiro State, including Serra da Bocaina National Park, Serra dos Órgãos National Park, Mata do Cedro Ecological Station, and Serra Nova State Park. This species is subject to ten threatening situations considering the municipalities of occurrence. These factors support our assessment of the extinction risk for M. porrecta as Least Concern (LC).

Figures

FIGURE 4. Trichomes types in Mimosa porrecta: A. Puberules or villose; B. Detail of porrect-stellate and glandular-subsessile (arrows); C. Porrect-stellate; D. Dendritic (H.C. Lima 2154, RB).

FIGURE 6. Inflorescence shape: conelike, in M. sensitiva var. sensitiva (A), and moriform, in M. sensitiva var. malitiosa (B) (A. D. Araujo 452, RB; B. S.A. Mori s.n., RB 204966).