Martiodendron mediterraneum (Mart. ex Benth.) R.C. Koeppen var. concinnum Barneby ex M.J. Falcão & Mansano

Falcão, Marcus José De Azevedo, Torke, Benjamin M., Garcia, Gabriel Santos, Silva, Guilherme Sousa Da & Mansano, Vidal De Freitas, 2023, A Taxonomic Revision of the Neotropical Genus Martiodendron (Fabaceae: Dialioideae), Phytotaxa 578 (1), pp. 11-56 : 42-43

Martiodendron mediterraneum (Mart. ex Benth.) R.C. Koeppen var. concinnum Barneby ex M.J. Falcão & Mansano . Var. nov. ( Figures 8 and 9 ).

Type:— Brazil: Minas Gerais: Águas vermelhas p/ Curral de Dentro , Mata. Árvore de até 20 m × 50 cm de diâm. Cálice amarelo-esverdeado, corola amarelo intenso, anteras marrom claro. 29-I-1965, Belém, R.P. 365 RB127412 Barcode 00145877 (Holotype: RB!; Isotypes: CEPEC!; IAN!; IPA; NY!; RB!; UB!) .

Diagnosis: — Martiodendron mediterraneum var. concinnum differs from Martiodendron mediterraneum var. mediterraneum by the shorter leaves, with 10–10.5 cm long, that are closer to each other forming more congested branches with the maximum distance between leaves 0.5–1.5(–2) cm; the terminal leaflets narrowly oblong, with a base obtuse, generally smaller and narrower, 2.5–6 × 1.1–1.6 cm; occurring in northern Minas Gerais.

Distribution, Biogeographical Comments and Habitat: —The variety is endemic to Brazil, occurring in far northern Minas Gerais, found in seasonal semideciduous forests on ecotone areas between the Cerrado, Caatinga and Atlantic Forest ( Figure 15 ). Its population is isolated in Minas Gerais, which may characterize a process of allopatric speciation. The existence of an old collection of M. mediterraneum var. mediterraneum in Bahia, an intermediate position between the main areas of occurrence of the two varieties, strengthens the idea of a possible original continuous distribution where, in the extreme south of it, a speciation process led to the emergence of a new taxon. Then there would have been an extinction event in the intermediate areas of both varieties.

Etymology: —Barneby proposed the name based on the Latin concinnus, meaning that the plant is elegant, beautiful, etc. Possibly due to the type specimen being characterized by a large number of inflorescences compared to the small foliage, as pointed out on the label of one of the specimens by the collector.

Taxonomic Comments: —In one of the duplicates of the specimen here selected as type (R.P. Belém 365) from the NY herbarium, we found a note made by the botanist Rupert Barneby, which included the name M. concinnum , never published, showing that he already considered this material as representative of a new taxon. However, due to the small number of differences between the two taxa and the considerable level of character overlapping, we chose to describe it as a variety and not as a species.

Undeveloped and smaller leaves may appear at the bases of the inflorescences of M. mediterraneum var. mediterraneum , sometimes being overdeveloped bracts on the axillae of the secondary axes of the inflorescence (A.J. Castro 72; L. Tyski 220; L.P. Queiroz 10188; among others). In these cases, the leaves are strongly decreasing in size towards the apex of the branch and the beginning of the inflorescence. Such undeveloped leaves can be confused with those of M. mediterraneum var. concinnum but, in this variety, the leaves with small leaflets occur uniformly throughout the plant.

Along with the morphological variation observed in M. mediterraneum var. mediterraneum , some relevant frequencies can be highlighted, differentiating this variety from M. mediterraneum var. concinnum . The bases of leaflets in var. concinnum are obtuse, while in the 152 specimens of mediterraneum observed here, 77% have a cordate base, 15% have a truncate base, and only 6% have an obtuse base. Concerning the maximum distance between leaves on the branch, concinnum has leaves 0.5–1.5(–2) cm apart, while 96% of specimens of mediterraneum have more than 2 cm of maximum distance between the leaves and 4% have 1-2 cm. Regarding leaf length and leaflet width, there is no overlapping of characters between the two varieties, with concinnum having leaves up to 10.5 cm long and leaflets up to 1.6 cm wide. In contrast, about 95% of mediterraneum specimens have leaves more than 12 cm long and leaflets with more than 2 cm wide and 5% of them have leaves 10.8-12 cm long and leaflets 1.7-2 cm wide.

Additional Specimens Examined: — BRAZIL: Minas Gerais: Itaobim, mata semidecídua. Árvore , 20 m × 65 cm DAP, 4-IV-1979, Rizzini, C . T . 1122 (RB).

Figures

FIGURE 8. Martiodendron mediterraneum (Mart. ex Benth.) R.C. Koeppen. A–D. Martiodendron mediterraneum var. mediterraneum; A. Habit; B. Branch with leaves and inflorescence; C. Detail of the petiolule and leaflet base; D. Detail of the axillary bud enveloped by the stipules; E–G. Martiodendron mediterraneum var. concinnum; E. Branch with leaves and inflorescence; F. Detail of the petiolule and leaflet base; G. Detail of the axillary bud enveloped by the stipules; H. Apex of the thyrsoid with cymose subunits presenting flower buds; I. Flower; J. Sepal; K. Stamen; L.Apex of anther with open pore; M. Detail of the base of the flower with sepals and petals removed showing the filaments of the stamens, the base of the carpel and the abaxial staminode; N. Gynoecium; O. Detail of the stigma; P. Branch bearing fruit; Q. Example of acuminate fruit apex; R. Seed. A: Storlaski, O.C. s.n.; B, J–O: Saddi, E.M. 356; C–D: Árbocz, G.F. 6202; E–G: Belém, R.P. 365; H: Árbocz, G.F. 6638; I: Cardoso, A. s.n.; P: Cardoso, D. 2974; Q: Castro, A.J. 72; R: Nascimento 1346. Drawn by M. Falcão. Scale bar.A: 1 m; B, E, P–R: 2 cm; C–D, F–G, K: 2 mm; H–J, N: 5 mm; L–M, O: 0.5 mm.

FIGURE 9. Martiodendron mediterraneum (Mart. ex Benth.) R.C. Koeppen. A–J: M. mediterraneum var. mediterraneum. A. Habit; B. Inflorescences with flower buds; C–D. Inflorescences with flowers in anthesis; E. Detail of the flowers; F. Detail of the densely flowered tree top; G. Detail of the tree top with fruits; H. Fruits; I–J. Typical leaves of M. mediterraneum var. mediterraneum with larger ovate to elliptical to oblong leaflets; K. M. mediterraneum var. concinnum. Leaves with smaller narrowly oblong leaflets. I: Saddi, E.M. 375; J: Pereira, J.B. 201; K: Belém, R.P. 365. Image authors:A–B, D: Oiliam Stolarski; C, E–F:André Cardoso; G–H: Hilda Melo and Guilherme Silva; I–K: REFLORA. Scale bar.A: 2 m; B, D, H: 5 cm; C, E: 2 cm; F–G: 10 cm; I–K: 5 cm.

FIGURE 15. Martiodendron distribution map. Topographic map of part of the Neotropics containing all analyzed specimens of the genus separated by species and varieties. Note the occurrence of most species in areas with elevations below 200 meters, with the exception of M. mediterraneum, which generally occurs in regions of elevation 200–600 meters. Source: NASA with modifications.