Piresianae

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 : 86-88

Synopsis for the ser. Piresianae (sensu Borges et al. 2022)

Series Piresianae Barneby.

Type — Mimosa piresii Barneby

Subshrubs or shrubs, prostrate or virgate. Stems unarmed. Microphyllidious or macrophyllidious, usually with few ample leaves, long efoliate terminal panicles or racemes. Indumentum smooth or scaberulous, with glandular setiform trichomes in little species and resinous stems in M. macropogon . Stipules firm or subfoliaceous, either lanceolate or narrowly triangular, the venation immersed. Leaves 1–28 jugate, and pinnae 5–42 pairs of leaflets. Blades 0.4–70 x 2.5–40 mm, 3–5-nerved. Globose capitula prior to anthesis either moriform or conelike; flowers 4-merous; calyx paleaceous-pappiform; corolla 2.6–5.45 mm, lobes 1-nerved; androecium diplostemonous, either cream-white or pink, shortly monadelphous. Pods subsessile or shortly stipitate, the shape linear, 25–66.15 × 5–9.55 mm, 4–12-seeded, the replum 0.4–2 mm wide; the articles either indehiscent or tardily dehiscent.

Distribution —This series has ten species occurring in Neotropical Savannas, southern Brazilian Amazonia, Rupestrian Grassland and Tropical Forest, in Bolivia and Brazil, distributed at high or low elevations.

Species— M. aguapeia Barneby , M. amolariensis L.H.P.Nogueira, A.L.B.Sartori & M.Morales , M. dasilvae A.S.L.Silva & Secco , M. huanchacae Barneby , M. kuhlmannii Hoehne , M. macropogon Barneby , M. piresii Barneby , M. orbignyana Barneby , M. riedelii Benth. and M. suberosa Atahuachi & C.E.Hughes.

Described by Barneby (1991), the Piresianae series originally included only the species M. kuhlmannii , M. macropogon , and M. piresii . Subsequently, M. dasilvae ( Silva & Secco 2000) and M. suberosa ( Atahuachi & Hughes 2006) were added to the ser. Piresianae because of their affinities to M. piresii . Borges et al. (2022), through phylogenetic studies in clade O, which was detected in the studies of Simon et al. (2011), which included ser. Pachycarpae and ser. Setosae, recognizing the monophyly of ser. Piresianae with the inclusion of M. aguapeia , M. orbignyana , and M. riedelii , these three previously placed by Barneby in ser. Setosae. Although M. huanchacae was not analyzed by Borges et al. (2022) in their study, we considered in it ser. Piresianae because of the affinity with M. aguapeia and the previous placement in ser. Setosae by Barneby (1993). Additionally, a sample of the specimen Simon 2326, which were previously identified as M. aguapeia and considered here as M. amolariensis , was located in the clade Piresianae ( Borges et al. 2022). It reinforces our hypothesis regarding M. amolariensis belongs to the series Piresianae .

Key for the identification of ser. Piresianae species

1. Leaves with pinnae 1-jugate; replum 1.5–2 mm wide ................................................................................................. M. kuhlmannii

- Leaves with pinnae 2–28-jugate; replum 0.4–1 mm wide .................................................................................................................2

2. Resinous stem; foliaceous stipules 1.5–3.5 cm long .................................................................................................. M. macropogon

- Non-resinous stem; subcoriaceous stipules 0.4–1.2 cm long.............................................................................................................3

3. Margin of leaflet glabrous; venation acrodromous........................................................................................................... M. suberosa

- Margin of leaflet strigose or pubescent; venation actinodromous......................................................................................................4

4. Procumbent shrubs; stipules 9 × 0.6 mm, linear-triangular; peduncles strigose ............................................................... M. dasilvae

- Subshrubs to shrubs virgate; stipules 3–12.25 × 1.4–4 mm, lanceolate, triangular, or ovate; peduncles densely silky ....................5

5. Leaf petiole 2.5–3 mm long; pinnae 18–28-jugate.............................................................................................................. M. riedelii

- Leaf petiole 16–60 mm long; pinnae 3–14-jugate..............................................................................................................................6

6. Leaflets 5–9-jugate; blades 10–25 mm wide........................................................................................................................ M. piresii

- Leaflets 17–35-jugate; blades 2.6–8.2 mm wide................................................................................................................................7

7. Trichomes hispid in stem, glandular trichomes absent in the petiole and fruits; calyx 1.4 mm long ......................... M. huanchacae

- Trichomes adpressed in stem, glandular trichomes often in the petiole and fruits; calyx (1.7–) 2.3–3.5 mm long............................8

8. Secondary veins of penultimate leaflets reaching the margin, areolation moderately developed and triangular; calyx lobes triangular.......................................................................................................................................................................... M. aguapeia

- Secondary veins of penultimate leaflets not reaching the margin, areolation moderately developed and quadrangular; calyx lobes truncate ...............................................................................................................................................................................................8

9. Largest penultimate leaflet up to 11.8 mm length; the center vein divides the blade 1:2; trichomes dense-setiform and yellowish in herbarium...................................................................................................................................................................... M. orbignyana

- Largest penultimate leaflet up to 21.5 mm length; the subcenter vein divides the blade 1:1:2; trichomes scattered-setiform and white-stramineous in herbarium................................................................................................................................. M. amolariensis

Distribution of ser. Piresianae

The ser. Piresianae species, restrict only to South America, occur in low elevation forests and hill formations at Brazil and Bolivia. ( Fig. 5 ). M. piresii Barneby is widely distributed in the Brazilian states of Mato Grosso , Pará , Tocantins and Beni, across locations below 250 m als; in the mountains, the species occurs at higher altitudes, with records of occurrence between 750–820 m such as Canaã dos Carajás (Pará). M. macropogon Barneby predominates in the southern forests of Amazonas, in lower altitude environments (50–185 m als). M. kuhlmannii Hoehne and M. dasilvae A.S.L. Silva & Secco , respectively, have been recorded in Rondônia and Pará, but there is no precise information about their site of occurrence.

In Bolivia, M. orbignyana occurs on hills above 700 m als, M. suberosa Atahuachi & C.E.Hughes and M. huanchacae Barneby are found in humid grasslands, Cerrado, and rocky outcrops of Campo Rupestre at altitudes of 200–850 m als. M. aguapeia , M. orbignyana and M. suberosa can be found in the Brazilian state of Mato Grosso, around the hills of Serra Ricardo Franco State Park. M. riedellii was only recorded from the Chapada dos Guimarães, Mato Grosso. Mimosa amolariensis occurs in the Serra do Amolar (Mato Grosso do Sul) and in the Serra de Santa Bárbara (Mato Grosso).

Figures

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