Steinbachiella leptoclada Harms

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/119855835/122063663

Conservation

VU - vulnerable

Lewis, G.P., Wood, J.R.I. & Lavin, M. Kew Bull (2012) 67: 789. https://doi.org/10.1007/s12225-012-9415-z

Type

Type: Bolivia, Prov. Sará, Dep. Santa Cruz, 400 m, Orilla de la Pampa, Río Palometillas, 25 Sept. 1924, J. Steinbach 6457 (isotype K!).

Morphology General Habit

Small deciduous unarmed tree (flowering branches often leafless), 4 – 8 m, habit and branching resembles someone standing with arms held slightly up with hands and fingers held horizontally, the terminal branchlets are much divided; bark greyish brown with young branches smooth, but becoming channelled or weakly fissured on older trunks, new stems and rachises of young flush foliage hairy, the hairs erect and somewhat curly, their bases and apices colourless, the central portion rusty brown, older lignified branchlets glabrous

Morphology Leaves Stipules

Stipules oblong to lanceolate, striate with prominent veins on outer surface, margins ciliate, caducous; leaves, which emerge from brown coriaceous perulate buds, 9 – 13-foliolate, leaflets short-petiolulate, narrowly oblong to oblong-oblanceolate, ovate or elliptic, apex obtuse, 10 – 22 × 5 – 10 mm, both surfaces sparsely pubescent with short, appressed hairs, venation slightly prominent on upper surface, secondary veins brochidodromous, tertiary veins reticulate

Morphology Reproductive morphology Inflorescences

Inflorescences axillary or terminal, 1 – 4-flowered racemes, flowers pedicellate, slender pedicels 5 – 6 mm long, a zone of disarticulation at the pedicel apex, just below the hypanthium, a pair of bracteoles present at the base of the calyx, these ovate to obovate, apex obtuse, outer surface sparsely pubescent, margins ciliolate, calyx obliquely cupulate-infundibuliform, c. 6 mm long, the calyx tube narrowing to a basal hypanthium, glabrous but for the ciliate calyx lobes, lowest calyx lobe lanceolate, acute , 3 – 4 mm long, the two lateral lobes acute, 2 – 2.5 (− 3) mm long, the two upper lobes rounded, 2 – 2.5 (− 3) mm long, all petals yellow, glabrous, standard petal suborbicular, 13 – 14 × 10 – 14 mm (including a 2 mm long claw), apex strongly emarginate, wing petals widely obovate, 13 – 15 × 6 – 6.5 mm (including a 3 mm long claw), petal lamina with a basal auricle, the apex rounded, keel petals 14 – 15 × 6 – 6.5 mm (including a 2 – 3 mm claw), petal lamina with a basal auricle, staminal sheath (9 + 1 stamens) 13 – 14 mm long, free portion of the filaments turned upwards, anthers homomorphic, 0.75 × 0.5 mm, ovary glabrous, stipitate, the stipe c. 10 mm long, ovary 3 – 4 mm long, style 3 – 4 mm long, tapering to a narrow terminal stigma

Morphology Reproductive morphology Fruits

Fruit a single seeded, stipitate, glabrous samara, 7 × 0.8 – 1.3 cm, (including a 1.5 – 1.7 cm long stipe), venation reticulate, the margin thickened, seed reniform to panduriform, 15 × 6 mm, the testa smooth, brown

Figures

Figs 3 and 4.

Distribution

Endemic to Bolivia. Map 1.

Ecology

From field observations the species is clearly a forest and not a cerrado species. It grows in Bosque Seco Chiquitano, where elements typical of Chaco forest are also present. In most of the locations it is known from, it is characteristic of forest transitional between these two types of woodland, but the records from Velasco and Beni lie indisputably within the Bosque Seco Chiquitano region.

Conservation

The records of Steinbachiella leptoclada represent scattered populations over quite a wide geographical area. Nevertheless, it is rarely found and in the three locations where one of us (JW) knows the plant, the population sizes are one plant, three plants and around 20 plants respectively. All three locations are vulnerable to forest clearance and this is probably true of many other places where the plant grows. Although there is not sufficient data at present to assign a firm conservation category within the IUCN system, this species is almost certainly vulnerable (VU).

Phenology

The species flowers abundantly, but very briefly, in Sept. and early Oct. and the short flowering period is a partial explanation for the small number of collections. It is possible that flowering does not take place every year. Certainly the tree from which Wood & Soto 26233 was collected was not in flower a year later, in the season and when other populations were in flower.

Note

There are a number ofMachaerium species that grow sympatrically with Steinbachiella leptoclada. These include M. acutifolium Vogel (common in the area, especially in cerrado vegetation), M. hirtum (Vell.) Stellfeld (in seasonally moist Chaco vegetation), M. opacum Vogel and M. nyctitansBenth. var. scleroxylon (Tul.) Hassl. (both locally rare) and M. villosum Vogel (seemingly the most similar in distribution to Steinbachiella locally). The predilection of S. leptoclada for Bosque SecoChiquitano and forest transitional between this vegetation type and Chaco forest contrasts with the general ecology of Machaerium, a genus most diverse in tropical wet forests or seasonal vegetation with more moisture availability or less pronounced seasonality compared to the seasonally dry tropical woodlands preferred by Steinbachiella . The legume Ateleiaguaraya Herzog parallels the distribution of Steinbachiella very closely within Bolivia, but also has been collected in Brazil (from semi-deciduous bush and cerrado, on sandy soil and rocky ground), from where Steinbachiella is currently not known.

International Legume Database and Information Service

Morphology General Habit

Perennial, Not climbing, Tree