Eriotheca saxicola Carv.

DE CARVALHO-SOBRINHO, JEFFERSON GUEDES, 2013, A new species of Eriotheca (Malvaceae: Bombacoideae) from Espírito Santo, eastern Brazil, Phytotaxa 108 (1), pp. 49-53 : 50-52

Eriotheca saxicola Carv. -Sobr., sp. nov. ( Figs. 1A–K , 2A–E )

Similar to Eriotheca parvifolia (Mart.) A. Robyns (1963: 150) in its diminutive habit and small leaves, but differing by its caducous leaflets, smaller flowers, and fewer stamens.

Type: — BRAZIL. Espírito Santo: Colatina, Alto Moacir, prop. Lalau , 19°20'37"S, 40°33'8"W, 11 September 2007 (lf, fl, fr), R. R. Vervloet et al. 3424 (holotype HUEFS!, isotype MBML!) .

Treelets, to 3 m tall, growing from a massive horizontal xylopodium-like organ; branches glabrous. Leaves palmately compound; petioles 5–50 mm long; stipules ca. 9 mm long, falcate, dorsiventrally flattened, caducous; leaflets 3(–5), caducous, chartaceous, fleshy, usually concave, appearing conduplicate, 25–120 × 13–34 mm, length-to-width ratio 1.2–3.4, elliptic, broadly-elliptic to semiorbicular, apex acute, base rounded, appearing cuneate, margin entire, revolute, glabrous on both surfaces; midrib prominent abaxially, secondary veins impressed, 8–11, tertiary veins reticulate; petiolules absent to strongly reduced. Inflorescences axillary, 1–6–flowered cymes; pedicels 8–20 mm long, bracteoles caducous; flower buds linear-oblong. Flowers 19–20 mm long, receptacles 2–3 mm long, with 1 whorl of glands; calyces 3–4 × 5 mm, cupuliform, truncate to crenulated, 5–lobed in fruit and persistent, outer surface minutely lepidote, brownish, inner surface sericeous; petals 19–20 × 4–5 mm, linear to oblanceolate, apex acute, tomentose with tufted and simple trichomes on both faces, sericeous towards the base, glabrous at 3 mm from base, brownish when dry, inner surface whitish when fresh; stamens 40–50, staminal tube 4–6 mm long, oblong, slightly expanded at apex, glabrous, producing free filaments 11–12 mm long, phalanges absent, anthers dorsifixed, reniform; ovary subglobose, pubescent, ferruginous, style inconspicuously 5-lobed. Capsules 35–50 mm long, woody, obovoid, outwardly glabrous, kapok abundant, brown, columella entire, marcescent. Seeds ca. 5 mm long, subglobose-angular, glabrous, and striate.

Distribution and habitat:— Eriotheca saxicola is probably endemic to granitic rock outcrops in the Rio Doce drainage in the northern region of the state of Espírito Santo, eastern Brazil. It is known only from six collections from the type locality, an inselberg named ‘Pedra do Cruzeiro’. Eriotheca saxicola inhabits an open, shrub, saxicolous vegetation at 700 m elevation.

Phenology:— Flowering from July to October and fruiting in July, September, and January.

Conservation status:— As it is currently known only from the type locality, Eriotheca saxicola must be considered Critically Endangered belonging to the Bla,b(i, ii) category ( IUCN 2010).

Etymology:— The specific epithet is from the Latin, in reference to the habit of the species on granitic rock outcrops.

Paratypes:— BRAZIL. Espírito Santo: Colatina, Alto Moacir, prop. Lalau , 19°20'21"S, 40°33'10"W, 12 July 2006 (lf, buds, fr), V. Demuner et al. 2578 ( MBML, SP); Marilândia, Liberdade, Pedra do Cruzeiro , prop. Aguilar Lovucini, 19°20'53.7"S, 40°33'03.6"W, 18 January 2006 (lf, fr), V. Demuner et al. 1647 ( MBML, SP); ibidem, 26 September 2006 (lf, fl), L. F. S. Magnago 1387 ( MBML); Marilândia, Liberdade, Pedra do Cruzeiro , 19°20'46"S, 40°32'59"W, 14 July 2011 (lf, buds), J. G. Carvalho-Sobrinho & R. O. Perdiz 3146 ( HUEFS); ibidem, 14 July 2011 (lf, buds), J. G. Carvalho-Sobrinho & R. O. Perdiz 3167 ( HUEFS) .

Eriotheca saxicola is a treelet to 3 m tall, a rare and rather distinctive trait among Eriotheca species. It is characterized by leaves with 3(–5) leaflets, leaflets elliptic to broad-elliptic, chartaceous, fleshy, usually concave, and caducous. In herbarium sheets, the leaves frequently appear to have 1–2 leaflets and leaflets are often folded. Eriotheca saxicola seems to be related to E. parvifolia , considered endemic to the areniticquartzite rock outcrops in the Espinhaço mountain range in the state of Minas Gerais, by the reduced individuals and small leaves and flowers. However, it differs in its caducous leaflets that are concave (versus leaflets persistent, plan), elliptic to broad-elliptic (versus obovate); smaller flowers (19–20 mm versus 25–35 mm long); narrower petals (4–5 mm versus 5–7 mm), tomentose (versus velutinous) petals; and fewer stamens (40–50 versus ca. 120).

Some herbarium specimens of Eriotheca saxicola have been misidentified as E. macrophylla , a large tree species with a widespread distribution that inhabits the Atlantic rainforest surrounding the type-locality. Such misidentifications could be attributed to the fact that some basal branches of E. saxicola are characterized by 5-foliolate leaves with longer petioles and leaflets reaching 5 and 12 cm respectively, while its fertile branches usually present 3-foliolate leaves and smaller leaflets. Nevertheless, E. macrophylla can be readily distinguished from E. saxicola by its overall larger leaflets (75–230 × 35–90 mm versus 25–120 × 13–34 mm; Fig. 2F ), larger petals (20–32 × 10–15 mm versus 19–20 × 4–5 mm), and by the more numerous stamens (90– 140 versus 40–50).

Moreover, Eriotheca saxicola presents an outstanding and novel morpho-ecological characteristic, which is the presence of a xylopodium-like organ. Although not common in Eriotheca species , some genera of Bombacoideae especially diverse in Seasonally Dry Tropical Forest vegetation (SDTF sensu Pennington et al. 2000) show strategies for coping with seasonal climates (e.g., succulence, deciduousness, waxiness). For instance, Adansonia L., Cavanillesia Ruiz & Pav. and Ceiba Mill. are pachycaulous with barrel-trunks for water-storage and Pseudobombax Dugand has a photosynthetic underbark. Therefore, the massive horizontal xylopodium-like organ of E. saxicola could be interpreted as an adaptation to the harsh edaphic and microclimatic conditions of inselbergs, with their high degree of solar radiation and high evaporation rates ( Porembski et al. 1998) that presumably exerted selection pressure on E. saxicola to adapt to this unique environment.

Figures

FIGURE 1. Eriotheca saxicola. A. Flowering branch. B. Detail of terminal branch showing stipule. C. Flower bud. D. Flower at anthesis. E. Petal. F. Detail of petal showing indument on adaxial surface. G. Staminal tube originating free filaments. H. Anther, front view. I. Anther, lateral view. J. Young capsule with persistent calyx. K. Seed. A–J. Vervloet et al. 3424. K. Demuner et al. 1647. Bars: A=2 cm; B–G, J–K=5 mm; H–I=0.5 mm.

FIGURE 2. A–E. Eriotheca saxicola. F. Eriotheca macrophylla. A. The granitic rock outcrop ‘Pedra do Cruzeiro’, general view. B. The open, shrub, saxicolous vegetation on the inselberg. C. Young individual with a massive horizontal xylopodium-like organ. D. Branch bearing appearing conduplicate leaflets and dehisced capsules. E. Detail of the xylopodium-like organ. F. Young individual cultivated at UEFS garden from material collected in the state of Espírito Santo. (Photos J.G. Carvalho-Sobrinho).