Mimosa serpensetosa L.M. Borges, 2014

Borges, Leonardo Maurici, Simon, Marcelo Fragomeni & Pirani, José Rubens, 2014, The census continues: Two new montane species of Mimosa (Leguminosae Mimosoideae) from Southeastern Brazil, Phytotaxa 177 (1), pp. 35-48 : 41-46

Mimosa serpensetosa L.M. Borges , sp. nov. ( Figs. 4–6 )

Mimosa serpensetosa is very similar to M. setosa var. paludosa (Benth.) Barneby , but differs from it particularly for being a prostrate subshrub (vs. erect shrub or treelet); and by its calyx rim with plane fringes gradually passing to filiform setae (vs. rim glabrous or ciliate not with filiform setae). Even though it shares a similar habit with M. setosa var. urbana Barneby , it differs from the latter by abundant presence of glandular setae (vs. almost or completely absent); presence of aculei (vs. absence); leaves’s rachis twice or more as long as the petiole (vs. ca. equally long); and absence of filiform setae on fruit’s valves (vs. presence). M. serpensetosa can also be distinguished from both species by its basal rachillas size ca. 1:2 of the medial ones (vs. 1:1).

Type:— BRAZIL. Minas Gerais : Santana do Riacho, Serra do Cipó, Estrada Santana do Riacho –Cardeal Mota, via Melo , cerrado de altitude, 19º13’34.5” S, 43º39’58” W, 814 m, 23 April 2006, fl., fr., L.M. Borges et al. 104 (holotype SPF!, isotypes BHCB!, K!, NY!, P!, RB!, UB!, US!)

Prostrate to decumbent shrubs with distal portion of stems ascending up to 30 cm, forming dense thickets of tangled stems getting up to 1 m tall, or more when synflorescences strongly assurgent; branches and often rachides armed with straight and broad-based aculei 2.5–5 mm long, with a caducous loose apex that may break up with time. Indumentum composed of simple trichomes, filiform setae and glandular setae with clavate head; branches, leaf axes, and peduncles pubescent with simple trichomes, hirsute with filiform setae 2–4 mm long and glandular setae 0.2–0.3 mm long; stipules and leaflets pubescent on both faces with trichomes (leaflet surfaces sometimes glabrescent or glabrous [Glaziou 10616; 19125]), also ciliate with both kinds of setae (glandular ones rarely present on abaxial surface of stipules and absent on leaflets margin); floral bracts abaxial surface pubescent with trichomes, hirsute with glandular setae and sparsely tomentose with filiform setae, adaxial surface glabrous to slightly pubescent with trichomes; fruits overall pubescent with trichomes and hispid with glandular setae 0.3–0.5 mm or 1.5–2.5 mm long (shorter ones usually restricted to margins and longer ones only to valves), margins also hirsute with filiform setae 2.5–3.4 mm long, surface not completely concealed by the indumentum. Leaves 7–15-jugate, except for the usually 3–5-jugate ones at the reproductive axis; stipules 3–5.3 mm × 0.6–0.7 mm, lanceolate-acuminate, reflexed, caducous to shortly persistent; petioles 12–30 mm long, 1–1.5 mm diam., grooved on adaxial surface, the pulvinus 1.5–2.5 mm long; rachis 45–110 mm long, 0.8–1 mm diam., grooved on adaxial surface and with a spiculate projection 1–1.5 mm long between each pinnae pair (sometimes caducous or randomly absent), terminal projection 2–3 mm long, linear; basal rachillas 10–18(–35) mm long, medial rachillas 15–52 mm long, distal rachillas 20–57 mm long, all 0.2–0.5 mm diam., 7–10 mm apart; leaflets 2.5–5.6 × 0.8–1.5 mm, 22–28 pairs on basal rachillas, 31–43 pairs on medial rachillas, 29–50 pairs on distal rachillas, narrowly-oblong, inequilateral, 0.6–1.5 mm apart, apex acute to rounded, base oblique, subcordate, rouded-truncate, 4–5(?) veins, slightly prominent only on abaxial surface; paraphyllidia 0.4–0.7 × 0.1–0.2 mm, subulate. Inflorescence a terminal or axillary exserted double-raceme, which may form a frondose and exserted paniculate synflorescence. Glomerules 7–1.2 × 7–9 mm, spherical to slightly ellipsoid, 2–3-axillary to a suppressed leaf that expands almost together with the anthesis of its associate glomerule and is fully expanded during fruit maturation; peduncles 18–32 mm long; floral bracts 3.1–3.9 × 0.5–0.7 mm, narrowly acuminate-spathulate, cymbiform, 1-nerved; flowers 4-merous, diplostemonous, basal ones only staminate; pedicel ca. 0.2 mm long; calyx (including lobes and indumentum) 1.2–2 mm long, cupulate, tube 0.3–0.5 mm long, lobes 1.1–1.9 mm long, indistinguishable, decompound in plane fringes gradually passing to filiform setae (very delicate in Glaziou 10616), a few glandular setae ca. 0.5 mm long sometimes present; corolla 3–4 mm long, infundibuliform, tube glabrous, lobes 1.1–1.5 × 0.9–1 mm, ovate, mucronate, 1-nerved, vein apex slightly prominent, tomentose with trichomes, filiform setae ca. 0.6 mm long and glandular setae ca. 0.2 mm long (the last absent in Glaziou 10616), indumentum not concealing lobes surface; filaments 10–11.5 mm long, glabrous, fused ca. 0.1 mm at base, pink; anthers 0.5–0.6 × 0.5–0.7 mm, glabrous; ovary 1.2–1.3 × ca. 0.7 mm, compressed, elliptic, margins tomentose with filiform setae 1.1–1.5 mm long and glandular setae ca. 0.1 mm long, stipe 0.2–0.3 mm long, glabrous; style 12.5–14 mm long, glabrous; stigma porate, glabrous. Fruit a craspedium 26–46(60) × 8–11 mm, narrowly oblong to oblong, papery, brown, apex obtuse to rounded, obliquely aristate, base cuneate, sometimes rounded; pedicel ca 0.5 × 0.5 mm; replum 1–1.1 mm wide; valves breaking together with seed liberation into 3–9 articles, central ones 4.5–5.1 × 7.8–9.2 mm, monospermic, transversely oblong; seeds 4.2–4.9 × 2.9–3.5 mm, ovate, lentiform, shiny dark brown, pleurogram present.

Additional specimens examined: — BRAZIL. Minas Gerais: Congonhas da Serra, fl., April–March [1887 (fide Urban, 1906)], A.F.M. Glaziou 10616 (K!, P?); [Itabirito] Capanema , s.d., fl., L. Riedel 8 (K!, LE!) ; [Itabirito], In campis sicois glareosis p. Capanema , fl., January 1825, L. Riedel s.n. ( LE!) ; Santana do Pirapama , Serra do Cipó , fl., 28 November 2009, A.P. Savassi-Coutinho et al. 1325 ( ESA, K!); acesso pela Fazenda Inhame , Estrada velha para a mina de manganês, subida da Serra , campo sujo, 18º55’3.44” S, 43º47’20.46” W, 1236 m, fl., 13 November 2009, D.C. Zappi et al. 2349 (K!, SPF!) ; Serra do Cipó ( Serra da Lapa ), Distrito de São José da Cachoeira , Estrada Santana do Riacho –Santana de Pirapama, trilha do Rio das Pedras, campo rupestre, fl., 20 February 2007, V.C. Souza et al. 32910 ( ESA, K!, SPF!); Fazenda Inhame (Serra Mineira), fl., 22 March 1982, J.R. Pirani et al. CFSC 8055 ( SPF!) ; Fazenda Toucan, trilha João Carrinho para trilha da Captação (A196), fl., 28 November 2009, G.O. Romão et al. 2411, ( ESA, K!); Trilha subindo o morro, 18º55’31.1” S, 43º47’37.3” W, 950 m, fl., 27 November 2009, A.P. Savassi-Coutinho et al. 1313 ( ESA, K!); Trilha subindo o morro, 18º55’31.1” S, 43º47’37.3” W, 950 m, fl., 27 November 2009, A.P. Savassi- Coutinho et al. 1309 ( ESA, K!); Santana do Riacho , Serra do Cipó , trilha IBAMA– Cardeal Mota, atravessando o rio Cipó com o barquinho, estrada logo após a travessia, próximo à pousada Pepalantus, borda de cerrado, fl., 18 June 2007, L.M. Borges & A. Ball 175 ( SPF!) ; Rodovia Belo Horizonte– Conceição do Mato Dentro (MG 010), km 119.5, margem direita, recuo na estrada, beira de estrada em área de campo rupestre, ca. 19º17’38” S, 43º33’50” W, fl., 14 June 2010, L.M. Borges et al. 432 ( SPF) ; trilha para a Lagoa Dourada a partir das imediações da Pousada Engenho Velho , cerrado, 19º25’08.9” S, 43º 37’34.1” W, 991 m, fl., 17 June 2010, L.M. Borges et al. 463 ( SPF!) ; Serra da Lapa , in glareosis sicois, January 1835, L. Riedel s.n. (G, P 03151826); Sertão, fl., October – November [1887 (fide Urban, 1906)], A.F.M. Glaziou 19125 (K!, P!) .

Distribution: — Mimosa serpensetosa is endemic to altitudinal cerrados and campos rupestres of Serra do Cipó (north to Belo Horizonte, Minas Gerais, Brazil, on quartizitic substrate), and with two records from iron rich soils of Serra de Capanema (south to Belo Horizonte) ( Fig. 4 and 6 A–B ).

Etymology: —The species’ name is derived from its creeping habit (“serpens”) and setose (“setosa”) indumentum, the latter also alluding to its similarity to elements of Mimosa setosa (sensu Barneby 1991) .

Conservation status: —EN. According to GeoCAT analysis results (EOO = 1823.27 km 2; AOO = 24 km 2) the species may be classified as Endangered. This is corroborated by a tendency to lost of habitat, since all collections from Serra do Cipó, were made outside of the Serra do Cipó National Park. However, it is highly likely that the species also occurs in protected areas within it. Its occurrence at Serra de Capanema, on iron-rich soils, is indicated only by a few ancient records, so it needs to be confirmed by a modern collection as soon as possible, due to mining pressure in the area. Nonetheless, if Capanema is excluded from the GeoCAT analysis, the values of EOO and AOO change respectively to 323.76 km 2 and 20 km 2, but the conservation status remains the same.

Notes: —The earliest collections of Mimosa serpensetosa were made by Riedel near Capanema, one in 1825 (Riedel s.n. [LE]), and the other without date information (Riedel 8 [K, LE]). Those are likely to be duplicates of the same collection event, but it is not possible to surely assert this. Specimens in G and P (Riedel s.n. [P 03151826]) indicate that Riedel also collected the species at Serra da Lapa, an early homonym for Serra do Cipó, in 1835. All modern collections of the species, however, are from Serra do Cipó, an area much more botanically explored than Serra de Capanema. It is not possible to assure that Riedel visited Capanema by January 1825, but in December 1824, Langsdorff’s expedition left Diamantina heading to Ouro Preto, where they were by the beginning of February. In January 28 th, Riedel left the expedition towards Serra do Caraça. There is no mention to Capanema in the diaries of the expedition, but is likely that he has reached the region, which lies close to Ouro Preto and Serra do Caraça (R. Mello-Silva pers. comm). In addition, M. foliolosa var. pachycarpa ( Bentham 1842: 406) Barneby (1991: 380) , a very common species from campos rupestres of Serra do Cipó, also occurs in altitudinal areas around Belo Horizonte that are close to Serra de Capanema, some of which have iron-rich soils. We believe this may reinforce the actual existence of M. serpensetosa in this area, as well as in others connecting it to Serra do Cipó, but its occurrence in this particular soil type must be investigated. Unfortunately, Capanema was mined and most of its original vegetation is missing.

Apparently the small size of the samples taken by Riedel and the lack of precise habit information, the species most distinguishing feature, made its true identity pass unnoticed by Bentham, who probably had access only to the specimen at Kew, which is mounted together with a collection of M. setosa var. paludosa (Riedel 584). Specimens latter collected by Glaziou were still identified as already known taxa by Taubert and also Barneby. The latter, however, left an extensive note in Glaziou 19125 (K) discussing its affinities and pointing out the need for further investigation, also present in his monograph under taxon “265bis. Mimosa sp ” ( Barneby 1991, 426–427). Borges & Pirani (2013 a) treated recent collections of M. serpensetosa as Mimosa setosa subsp. setosa , supposing an unconfirmed relation with M. setosa var. pseudomelas due to the lack of interpinnal projections. The projections are in fact present in both species, but may easily fall and hence seem absent, and M. serpensetosa is strongly dissimilar from this particular variety, markedly by type of habit, presence of aculei and leaf and fruit morphology.

Of the Mimosa species used for delimitation of M. serpensetosa (see Material and Methods), two ( M. setosa var. paludosa and M. setosa var. urbana ) were compared with it at the diagnosis above. It is important to highlight that M. setosa var. urbana is distantly allopatric, occurring in cerrados surrounding the Federal District in Central Brazil. The other two, M. lithoreas and M. chiliomera , are the only humifuse species of Mimosa ser. Pachycarpae known to also occur in altitudinal areas of Minas Gerais state. M. lithoreas , which is known from only two collections, including the type, from campos rupestres surrounding the municipalities of Paracatu and Coromandel, may be differentiated by the lack of glandular indumentum in vegetative organs as well as prickles (vs. presence), apressed filiform setae (vs. patent), glabrous corollas (vs. tomentose), and by its non-dehiscent craspedia. M. chiliomera is endemic to Serra do Cabral and its following main characters may be used to distinguish it from M. serpensetosa : absence of interpinnal projections (vs. presence), absence of setae on leaflets margin (vs. presence), corolla indumentum compound only by simple trichomes and filiform setae that conceal the lobes’ surface (vs. presence of triple indumentum not concealing the surface), as well as its prominent number of pinnae pairs (ca. 38 vs. 7–15), considered by Barneby (1993) as its most remarkable feature. Table 2 summarizes the main diagnostic characters between M. serpensetosa and the related species here highlighted (a complete nexus table showing all variable features between the species is provided at http:// dx.doi.org/10.7934/P1220) .

lithoreas and M. chiliomera . See text for further information not provided and comments

Mimosa serpensetosa may be superficially mistaken with M. foliolosa var. pachycarpa , but the latter is a shrub with incurved ascending branches, with leaves lacking interpinnal projections of any kind, and its fruit is a nonarticulated craspedium.

Specimens from Santana de Pirapama, located at the northwestern portion of Serra do Cipó and which was recently extensively surveyed ( Zappi et al. 2014), tend to present bigger leaves, leaflets and glomerules, coarser filiform setae, as well as not to show the markedly villous branches that are seen on other specimens. Since those are mainly allometric variations, they are interpreted here as intraspecific geographical variation. Also, the majority of collections from this area, although not in detail, indicate the plants as being shrubs from 40 up to 100 cm and even 150 cm tall. That may cast doubt on the use of habit as a valid character to delimit the species. However, individuals from the southern portion of Serra do Cipó were observed forming dense thickets of interlaced stems ( Fig. 6 C ), what may explain how the species can reach up to 100 cm tall, and, if the synflorescence is greatly exserted and assurgent, maybe up to 150 cm. According to G.P. Lewis (pers. comm.), who has been collecting in Santana de Pirapama, the plants collected there were prostrate spreading shrubs that fit perfectly this scenario.

It is interesting to note that the fruits of Mimosa serpensetosa have typical craspedial dehiscence, but part of the articles tends to remain united at least partially ( Fig. 5 L ). This adds to the evidence that the main feature segregating M. ser. Setosae from M. ser. Pachycarpae may be artificial ( Simon et al. 2010).

Figures

FIGURE 4. Distribution map of Mimosa perplicata (▲) and M. serpensetosa (●).

FIGURE 5. Mimosa serpensetosa. A. Habit. B. Branch. C. Leaf. D. Stipule (abaxial surface). E. Adaxial surface of leaflet. F. Abaxial surface of leaflet. G. Branch detail showing the triple indumentum of trichomes, filiform setae and glandular setae, aculei with loose apex (la) and after fall of apex (af). H. Detail of the rachis showing the interpinnal projection. I. Floral bract. J. Hermaphrodite flower. K. Masculine flower. L. Fruit. M. Seed. Drawing by Laura Montserrat.

FIGURE 6. A–C. Mimosa serpensetosa. A. Trailing branch. B. Exserted synflorescence. C. Interlaced branches self-raising the plant from soil level. D. Synflorescence of M. setosa var. paludosa Benth. Photos A–C by C.M. Siniscalchi; D by G.P. Lewis.