Mimosa serra Burkart

Morales, Matías, Keller, Héctor & Fortunato, Renée H., 2022, Mimosa serra (Caesalpinioideae, Fabaceae): conservation insights and its presence in Argentina, Phytotaxa 574 (3), pp. 241-250 : 244-246

Mimosa serra Burkart , in Reitz, Fl. Ilustr. Catarin. LEGU(l): 200, est. 32, 33. 1979.

TYPE:— BRAZIL. Paraná: São Mateus do Sul , 10 km para o Oeste, 09 February 1966, fl., Hatschbach, J. Lindeman & H. Haas 13792 (holotype SI! ; isotype P!, NY 3043!, 3044!, RB!, SP366472 !, US) .

Subshrubs 2–6 m tall, erect, sometimes with some decumbent branches. Stems and branches 3–4–ribbed, armed with cat–claw aculei in several ribs, glabrous to puberulent. Leaves with stipules of 2.5–12 × 2–7 mm, ovate to triangular, glabrous, ciliate in the margin, 12–25–nerved, persistent; petioles 2–8.2 cm long; pinnae 1–pair; secondary rachis 2–8 cm long; leaflets 25–35–pairs, 3–19 × 1–3.8 mm, oblong to elliptic, glabrous on both faces, with ciliate margin, 4–5–nerved, brochidodrome venation when visible. Synflorescences notably exerted with peduncles 5.5–20.4 mm long; capitula 5.5–9.5 × 5.5–6 mm, spheroid to ellipsoid; floral bracts 2–3 mm long, oblanceolate, ciliate in the margin, 1–nerved. Fertile flowers 4–merous, 4–androus; calyx 0.15–0.5 mm long, campanulate, glabrous or bearing some setae in the margin; corolla 2–3.5 mm long, glabrous, 1–nerved; androecium with free stamens and pink filaments; gynoecium with ovary puberulent. Craspedia 10–16 × 4–5 mm, breacking into 3 articles, with marginal replum, persistent, straight or barely undulate and hispid; valves glabrous on surface and articles 4–4.5 × 2–3 mm, 1–seeded. Seeds 2.5–3 mm in diameter, lentiform, castaneous.

Taxonomic notes: — The set of specimens from this population exhibit a morphology similar to the original circumscription of M. serra and they can be identified according to the proposal of Barneby (1991). This species remotely resembles M. polycarpa by the calyx campanulate and the growth habit, but it is clearly distinguishable from that by the presence of cat’s claw aculei on the 3–gone (not terete) stems. Barneby (1991) found that M. serra is “technically similar” to M. lundiana Bentham (1875: 395) and M. insidiosa Martius (1838: 54) , but both are clearly distinguishable by the stipules only 3–5–nerved, the indumentum (eglandular in M. serra , glandular in M. lundiana ) and the presence of retrorse setae in M. insidiosa . M. serra has a consistent morphology according to the classification proposed by Barneby (1991) as monotypic subseries Serrae Burkart of the series Mimosa .

Geographic distribution and ecology: — M. serra occurs in southern Brazil (Paraná and Santa Catarina states), eastern Paraguay (Itapúa) and northeastern Argentina. This species is reported for the first time for the province of Misiones in northeastern Argentina, and grows in sporadically flooded grasslands (denominated brejo in Brazil or pajonal in Argentina), in communities frequently dominated by Andropogon lateralis Nees (1829: 323) and on the edge of roads.

Selected specimens examined: — ARGENTINA. Misiones: San Ignacio, Villa Ema ; 17 January 2021, Keller & Ramírez 14417 (CTES, BAB) . BRAZIL. Paraná: Guarapuava, Posto Agropecuario, 27 April 1968, fl.-fr., Hatschbach et al. 19186 (MBM 6973); Palmas : Fazenda São Geraldo , fl., no date, Motta 2333 (MBM 296871); Colonia Iguaçú , 20 April 2009, fr., Silva et al. 7176 (CESJ 59457, MBM); rio Potinga , 22 February 1972, fl., Hatschbach et al. 29166 (NY 443277); Várzea da Olaria [near Rio Potinga], 16 January 2006, fl., Ribas et al. 7169 (ALCB, MBM) . Santa Catarina: Porto União: Between Fazenda Frei Rogerio and Rio Pintado , southeast of Porto União , 04 February 1957, fl., Smith & Klein 10783 (paratype, US 2449375) . PARAGUAY. Alto Paraná: Estancia Río Bonito , S of Forest III, 28 February 1996, Zardini et al. 44712 (BAB, MO), same locality, 25°38’30”S 054°49’01”W, 28 February 1996, Zardini et al. 44725 (BAB, MO) .

Conservation status of Mimosa serra

Global parameters:

- Number of subpopulations: 8.

- Number of locations: 5.

- EOO: 55,000 km 2.

- AOO: 36 km 2.

- Possible threats: There are three areas with populations of this species: 1) southern Brazil (Paraná and Santa Catarina), when most of the populations are concentrated, and two isolated populations in 2) Paraguay, and 3) Argentina. The populations are located in areas of seasonally flooded grasslands and most of them are immersed in a matrix of native subtropical forests, plantations and agriculture lands. In Brazil, most of the populations occur in surrounding urban and suburban areas of São Mateus do Sul (Paraná state). The presence of the species in anthropic areas coincides with a possible continuing decline of the extent and quality of the habitat.

- Assuming the Criterion B of the IUCN Guidelines, we proposed Endangered EN B2 a,b (iii) as the global status of Mimosa serra , since the AAO is in the range 10–500 km 2, and two additional conditions are met: 1) this species is severely fragmented, with most of their populations distanced far away more than 100 kilometers and located in small patches of swamp or grassland immersed in a matrix of agriculture and forests; 2) this species is growing in areas with an inferred risk of continuing decline.

Argentine population parameters

- Location: Misiones, Argentina.

- Number of subpopulations: 1.

- Number of locations: 1.

- Area of the population: Around 1 km 2.

- Number of mature individuals: 325.

- Percentage of mature individuals: 96%.

- Individuals with sanitary problems: 6 (minor damage by insects).

- Possible threats: The area is a seasonally flooded grassland surrounded by dense subtropical forests and Eucalyptus grandis W.Hill ex Maiden (1918: 501) plantations. In some parts there are isolated individuals of Pinus Linnaeus (1753b: 1000) and a population of Hedychium coronarium J. Koenig (1783: 73) at the edge; both species are invasive in the region. This situation evidence possible continuing decline of the extent and quality of the habitat.

- According to the criterion B, since: 1) the AOO is ca. 1 km 2, 2) M. serra has only one subpopulation/location in Argentina, and 3) a continuing decline in quality and extension of the habitat can be estimated, this species should be categorized as Critically Endangered (CR B2 a,b(iii)).

- According to the criterion C, since: 1) the population had a number of mature individuals ranging 250–2500, 2) a continuing decline can be inferred in some subpopulations and 3) it met the condition C2 A ii: the number of mature individuals in one subpopulation is ranging 95–100%, this species should be categorized as Endangered (EN C2 a(ii)),

- According to the criterion D, since the number of mature individuals ranged from 250 and 1000, the status of this species should be categorized as Vulnerable (VU D1).

- Although using different criteria it is possible to infer different conservation status, we considered that the preliminary categorization for M. serra for Argentina should be Critically Endangered, under the B criterion (CR B2 a,b(iii)); it reflects the most severe conservation scenario for the species.