Mimosa amolariensis L.H.P.Nogueira, A.L.B.Sartori & M.Morales, 2024

Nogueira, Luan H. P., Morales, Matías & Sartori, Ângela L. B., 2024, A new species of Mimosa (Leguminosae, ser. Piresianae) from the Brazilian Midwest, Phytotaxa 662 (1), pp. 80-92 : 82-85

Mimosa amolariensis L.H.P.Nogueira, A.L.B.Sartori & M.Morales sp. nov.

Type:— Brazil. Mato Grosso do Sul: Corumbá, Serra do Amolar , Fazenda Morro Alegre , 18°01’24.28”S, 57°31’46.90”W, 496 m, 26 July 2023 (fl. and fr.), LHP Nogueira 291 (holotype: CGMS!) . ( Figs. 1–5 )

Mimosa amolariensis can be differentiated from M. aguapeia Barneby by the poorly developed venation (versus robust venation), non-anastomosing secondary veins (versus anastomosing secondary veins), and truncate calyx lobes (versus triangular calyx lobes).

Subshrub or erect shrub, 1–2 m tall. Subshrub or erect shrub, 1–2 m tall. Horizontal underground structures, the primary and old roots ligneous, the secondary roots brown, with brownish-orange lenticels, and inside cream-orange. Branches with filiform, setiform-barbellate, and glandular-setiform trichomes. Aculei absent. Stipules persistent, (3.95–)6.1–12 × 1.4–3.1 mm, base truncated, apex acute-attenuated, 6–10-nerved; glabrous abaxial surface, pubescent filiform, dense setiform-barbellate and granular trichomes on the adaxial side. Cylindrical petiole, 22.1–45.15(–48.9) mm, pubescent filiform, dense setiform-barbellate, granular and occasionally glandular-setiform trichomes. Rachis 49.2–124.3(–140) mm, pubescent filiform, dense setiform-barbellate and rare glandular-setiform trichomes; spicule absent. Pinnae (4–)5–9(–14) of pairs; petiole 2.5–3.9 mm, pubescent filiform, dense setiform-barbellate and rare glandular-setiform trichomes; paraphyllidia present. Rachilla (21–)24.6–105(–115.5) mm, pubescent filiform, dense setiform-barbellate trichomes. Leaflets (5–)17–35 jugae; pulvinule with adpressed setiform trichomes; blade 8–21.45 × 2.6–8.2 mm, elliptical-oblong, base oblique, apex acuminate; 4–5-nerved, secondary veins not anastomosed; glabrous or with adpressed filiform and setiform-barbellate trichomes on both sides; the margin ciliated filiform, setiform-barbellate and rare glandular-setiform trichomes. Synflorescence in terminal panicle or raceme. Inflorescence capitula, prior to anthesis conelike; peduncle 12.1–32.3 mm, dense pubescent filiform, setiform-barbellate and occasionally glandular-setiform trichomes. Flowers subsessile, tetramerous, with staminate flowers concentrated at the base and perfect flowers in most of the inflorescence; calyx pappiform, (1.7–) 2.95–3.5 mm, reaching just over half of the corolla, lobes truncated with long-setiform ciliated trichomes; corolla trumpet-shape, 3.3–5.45 mm, 1-nerved, lobes with long-adpressed trichomes; androecium with pink-white styles, diplostemonous; gynoecium stipitate, oblongobovate, trichomes dense glandular-capitate and granular. Articulated craspedia, 37.2–66.15 × 8.7–9.55 mm, chestnutbrown, trichomes pubescent filiform, adpressed setiform and dense glandular-setiform, 4–9 articles. Seeds obovatewidely depressed ovate, copper-brown, pleurogram apical-basal.

Taxonomic notes —We considered that M. amolariensis as belonging to the ser. Piresianae sensu Borges et al. (2022), since the presence of efoliate panicles and racemes, filiform setae in the pedicel, calyx paleaceous-pappiform, corolla funnelform-like (trumpet-shaped). In addition, the phylogenetic position of this species coincides with the placement in the ser. Piresianae . It was detected by the inclusion of a distinctly identified sample in recent phylogenetic analyses ( Borges et al. 2022). The representatives of this series have leaflets more than 10 mm wide ( M. kulhmannii , M. macropogon , M. piresii and M. suberosa ) or leaflets less than 10 mm wide ( M. aguapeia , M. amolariensis , M. dasilvae , M. huanchacae , M. orbignyana and M. riedelii ). Among the species with leaflets up to 10 mm wide, M. amolariensis stands out by glandular trichomes in petiole and craspedia (in contrast to petiole and craspedia without glandular trichomes in M. dasilvae , M. huanchacae and M. riedelii ), the largest penultimate leaflet more than 12 mm length and the excentric veins divide the blade in 1:1:2 (opposite to M. orbignyana in which the largest penultimate leaflet up to 12 mm length and the central vein divide the blade in 1:2), the secondary veins not anastomosed and the lobes of calyx truncated (unlike the secondary veins anastomosed and the lobes of calyx triangular in M. aguapeia ).

Distribution and habitat —To date, Mimosa amolariensis has four known populations in the Serra do Amolar (Mato Grosso do Sul) and Serra de Santa Bárbara (Mato Grosso), in rocky outcrops of Campo Rupestre and Cerrado Rupestre at altitudes of 496–920 m asl. In hills of Serra do Amolar, M. amolariensis occurs in higher altitude areas, where the vegetation consists of grasses (different Poaceae species), Vellozia variabilis Mart. ex Schult. & Schult.f. , and Mimosa xanthocentra Mart. var. xanthocentra also occur, as well as scattered woody species such as Diptychandra aurantiaca Tul. , Kielmeyera rubriflora Cambess. , Miconia ferruginata DC. , Styrax ferrugineus Nees & Mart. , and Zeyheria montana Mart. In the restricted population at Morro Alegre hill (Serra do Amolar), we found six individuals in dried stream, between rocky outcrops, behind the top of the hill ( Fig. 3 ).

Phenology —Flowering and fruiting occur between March and July and individuals having only fruits were recorded until September. Some morphological traits, such as dehiscent articles, suggest that autochory is the main syndrome related to fruit dispersal. We did not detect morphological traits related to other syndromes.

Ecology— Mimosa amolariensis is characterized by robust underground structures above the rocky outcrops, phenolic compounds stored in its morphological anatomy, and high fruit production ( Figs. 4 and 5 ). These traits are associated with the ability to permanency and regrow after periodic natural or anthropological fire events in Serra do Amolar and Serra de Santa Bárbara, including the presence of phenolic compounds, highly associated with protecting the species and increasing its tolerance to fire ( Simon et al. 2009; Palermo & Miranda 2012; Lamont et al. 2018; Santacruz-Garcia et al. 2021a; Santacruz-Garcia et al. 2021b; Silva et al. 2021; Siqueira et al. 2023). The presence of phenolic compounds was detected in other fire-tolerant plants from the Brazilian Pantanal, such as Cassia grandis L.f., Handroanthus heptaphyllus (Vell.) Mattos , Inga vera Willd. , Ocotea diospyrifolia (Meisn.) Mez , Rhamnidium elaeocarpum Reissek , Triplaris americana L., T. gardneriana Wedd. and Vitex cymosa Bertero ex Spreng. (Silva et al. 2021; Siqueira et al. 2023).

Etymology —The specific epithet amolariensis refers to the location of the first recording of the species, the Serra do Amolar.

Specimens examined — Brazil. Mato Grosso do Sul: Corumbá: Reserva Acurizal, Serra do Amolar , borda oeste do Pantanal , fl. and fr., 17°54’27.0”S, 57°34’8.0”W, 710 m, 10 May 2003, A Pott 11213 (CGMS) ; Serra do Amolar, Pico do Morro do Mandioré , only fruits, 18°02’37.0”S, 57°32’47”W, 920 m, 14 Sep 2008, GA Damasceno-Júnior 5105 (CGMS) ; Serra do Amolar, Fazenda Morro Alegre, fl. and fr., 18°01’24.28”S, 57°31’46.90”W, 496 m, 26 Jul 2023, LHP Nogueira 291 (CGMS). Mato Grosso: Pontes e Lacerda, Serra de Santa Bárbara , 45 km em vicinal a partir do km 28 da MT-473, ao sul de Pontes e Lacerda, only flowers, 15°41’10.00”S, 59°21’41.99”W, 540 m, 24 Mar 2014, MF Simon 2326 (CEN) .

Figures

FIGURE 1. Mimosa amolariensis. A. Flowering branch. B. Stipule. C. Leaflet, adaxial surface; D. Leaflet, abaxial surface. E. Flower. F. Ovary. G. Fruits. H. Seed.A–B and G–H A Pott 11213; C–F LHP Nogueira 291.

FIGURE 2. Venation patterns of subterminal leaflets. A. Mimosa orbignyana. B. M. amolariensis. C. M. aguapeia.

FIGURE 3. Plant on rock-soil environment in Serra do Amolar (Mato Grosso do Sul). A. Virgate habit of Mimosa amolariensis, plant on rocky outcrop and among savanna grassland. B. White inflorescences. C. Immature fruits.

FIGURE 4. Shallow storage root of Mimosa amolariensis. A. Major root and secondary roots. B. Secondary root section showing the cortex.

FIGURE 5. Cross-section of the root of Mimosa amolariensis showing phenolic compounds, indicated by white arrows.