Dicorynia paraensis Benth. var. ingens (Ducke) R.C. Koeppen (1967)

Falcão, Marcus José De Azevedo, Torke, Benjamin Marland & Mansano, Vidal De Freitas, 2022, A Taxonomic Revision of the Amazonian Genus Dicorynia (Fabaceae: Dialioideae), Phytotaxa 554 (1), pp. 1-31 : 25-26

Dicorynia paraensis Benth. var. ingens (Ducke) R.C. Koeppen (1967) Brittonia 19(1): 55

≡ Basionym: Dicorynia ingens Ducke (1925) . Arch. Jard. Bot. Rio de Janeiro 4: 58. TYPE:— BRAZIL. Pará: Oriximiná ad flumen Trombetas infer, in ripis. Arbor media fl. albis, 4-III-1915, Ducke, A. s.n. MG15707 (Lectotype: MG!; Isolectotype: BM!, G, K!, NY!, R!, RB!, U!, US!, US!). Designated by R. C. Koeppen (1967).

Large trees. Leaves (20–) 26–50 cm long (probably even larger due to some duplicates with big leaflets detached from the rachis), leaflets (9–) 11, terminal leaflets broadly ovate to broadly oblong, cordate to slightly truncate at base, the abaxial face pubescent, papillate, with conspicuous red to brown glandular trichomes visible under a stereomicroscope, (9–) 10–21 × 5.5–13 cm, the length less than 2 times the width; petiolules 3–4 (–7) mm long; axillary buds non-deciduous, orbicular, obtuse at apex, ca. 3 × 2 mm, close to the leaf attachment point, less than 0.5mm above it. Inflorescences ca. 20–30 cm long, pilose, dark brown, secondary branches perpendicular to the central axis or ascending; indumentum of the external face of the sepals and petals golden to brown. Fruits 4-4.5 × 3 × 0.4 cm. (Figs. 6H; 7D; 8D–G).

Distribution, Habitat, and Ecology: — D. paraensis var. ingens is known from only two collections from the banks of Trombetas River near Oriximiná in western Pará, Brazil. These two collections were both made by Ducke and may have possibly originated from the same individual (see taxonomic comments). While the habitat was not clearly described, the location of the type locality on the riverside suggests a distinction from D. paraensis var. macrophylla , the only other variety of D. paraensis in Pará, which usually occurs in “terra firme” forests. Their exact size is unknown, with only the mention of being tall trees.

Etymology: —The epithet is from Latin, meaning large and unusual.

Phenology: —Flowering in March, fruiting in April.

Conservation: — With only two specimens collected in a single region more than 90 years ago, Dicorynia paraensis var. ingens might be considered Critically Endangered, or even a possibly Extinct, applying IUCN criteria A – D. However, given imprecise collection data and the under collected surrounding region, we place it in the “Data Deficient” category .

Taxonomic Comments: — Dicorynia paraensis var. ingens can be distinguished from D. paraensis var. paraensis by the generally larger leaves, larger number of leaflets, smaller petiolules, and shape of the axillary buds. It differs from variety uaupensis due to the generally larger leaves, larger number of leaflets, wider leaflets, base of the leaflets cordate to truncate, smaller petiolules, and shape of the axillary buds. Finally, from D. paraensis var. macrophylla due to the wider leaflets, shorter petiolules, shape of the axillary buds, and environment of occurrence possibly in flooded forests (Table 1).

Koeppen (1967) considered variety ingens a morphologically variable taxon from Pará, even though only four specimens were known until then. Those specimens bear little vegetative resemblance to each other, one of them with the largest leaflets of the genus and other with small leaflets of a different shape and distinct axillary buds. Differences in size and shape of floral organs used by Ducke (1922, 1925, 1948) to diagnose D. ingens , the basionym of D. paraensis var. ingens , were discarded by Koeppen (1967), who distinguished it based on the leaflets with glandular trichomes, the indumentum on leaves and revolute margins, and the dark brown, pilose inflorescences axes (Koeppen used the term velutinous which not properly describe the character). Such characters are really present in all four syntypes of var. ingens plus a fifth specimen recently collected in Pará (S.M. Faria 1072), plus one from the Maués River in adjacent eastern Amazonas (K. Kubitzki 87-29). However, similar glandular trichomes occurs in some distant specimens of var. macrophylla (M.J. Falcão 90; Cardoso, D. 3397), var. paraensis , (A. Ducke s.n. RB35072) and var. uaupensis (A. Ducke s.n. RB35075; Coelho, L.F. 656). As for the leaf indumentum, there are several similar specimens in varieties macrophylla and uaupensis . Besides that, both characters vary strongly in degree even among the syntypes of var. ingens . The revolute margins are not constant even among the syntypes. The inflorescence indumentum of the five specimens from Pará and one from Maués River, while showing some variation in degree, is indeed different from the rest of the species. However, it is important to emphasize that a wide range of colors can be found through the species with several shades of golden and brown.

Among the four syntypes of var. ingens , the morphology of leaves and axillary buds show two differentiated groups: one that fits within the delimitation proposed here for var. macrophylla (A. Ducke 16696; 11014 in Almeirim and Gurupá regions), and another group containing the lectotype of var. ingens (A. Ducke 15707; 16022 in Oriximiná region), being plants exceptionally differentiated from var. macrophylla and other varieties. Thus, we were confronted with two main taxonomic hypotheses for var. ingens : 1- Covering the four syntypes and two newer collections, only var. ingens would occur in Pará, extending to Maués River in Amazonas, strongly varying morphologically and the only distinctive characters from var. macrophylla would be a greater number of glandular trichomes in leaflets and the pilose and dark brown inflorescences (both characters varying in degree, even within only six specimens, and the former existing in some specimens of other varieties); and 2- The hypothesis here proposed, with var. ingens restricted to Oriximiná, consisting of two specimens that are unique in the combination of leaf/leaflet size and shape, petiolules length, and axillary bud size/shape. It seems possible that the two collections were gathered at different times from the same tree, since Ducke (1948) indicated that he had observed only a single individual in the region. Being so, the specimens from eastern Pará and the Maués River are otherwise compatible with var. macrophylla , which would remain vegetatively and geographically stable with the inclusion of these individuals, in addition to having some scattered specimens with more glandular trichomes. A possible weakness for this hypothesis is the great frequency of darker pilose indumentum in the eastern most populations of var. macrophylla , similar to var. ingens , which could indicate the existence of gene flow due to the intercrossing between the two varieties in Pará. Thus, until now, the mentioned evidences led us to maintain var. ingens as a differentiated infra-specific taxon, although closely related to var. macrophylla and with a reformulated morphological/geographical delimitation.

It is worth mentioning that, more than fifty years after Koeppen’s work, apparently only one new specimen of Dicorynia was collected in Pará (S.M. Faria 1072), which may indicate a rarity of the genus in this region, since many riverine areas in the state have been widely sampled in recent decades. It should also be noted that a large amount of Fabaceae materials from the region were observed here and no new specimens of Dicorynia were found. The only recent collection for Pará also falls within the delimitation proposed here for var. macrophylla , collected in Trombetas River, north of the area of occurrence of var. ingens . Furthermore, the question remains as to whether var. ingens still exists, 80 years after the last collections in a region that has suffered huge anthropic environmental impacts in the past decades.

Additional Specimens Examined:— Brazil.— PARÁ: Oriximiná, Trombetas, 11-IV-1916, Ducke , A. s.n. MG16022 ( BM; MG; P; RB; US) .