Pilea carautae M.D.M.Vianna & R.J.V.Alves

Filho, M.D.M.V. & Alves, R.J.V. 2010. Pilea carautae (Urticaceae), a new and endemic species from South-eastern Brazil. Kew Bulletin 65: 469. DOI: https://doi.org/10.1007/s12225-010-9222-3

Morphology Reproductive morphology Inflorescences

Staminate inflorescences branched, 5 – 10 mm long, dichasia compact, with 5 – 9 flowers, mature peduncle up to 5 mm long, glabrous; pedicels 1 – 2 mm long, 0.5 mm in diam., glabrous Inflorescences unisexual, bracteate, 0.3 mm long, in pairs, either both pistillate or one of each sex

Morphology Reproductive morphology Flowers

Staminate flowers with 4-lobed perigonium, tepals ovate, subapical appendices c- 0.2 mm

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 4, filaments c. 1.5 mm and anthers c- 0.5 mm long; pistillate inflorescences 1 or 2 per axil, 10 – 25 mm, bearing 11 – 15 flowers in a single compact dichasium, peduncle 0.5 – 1 mm long; pedicels c- 2 mm long, pistillate flowers oval to 0.5 mm long; perigonium unequally 3-lobed; central lobe larger and ovate; lateral lobes smaller and lanceolate; stigma 1, penicillate, hyaline

Morphology Reproductive morphology Fruits

Achenes c- 0.8 mm long, asymmetric, ovate

Distribution

Brazil: Rio de Janeiro, Mun. Cabo Frio, Arraial do Cabo and Armação dos Búzios (collections marked by stars in Map 1). Known only from the Cabo Frio Diversity Centre, a recognised floristic hotspot, from the municipalities of Cabo Frio, Armação dos Búzios and Arraial do Cabo. The largest known populations are on the small island of Cabo Frio, which belongs to the latter municipality and from where many cases of endemism have already been reported (Leme1985; Tatagiba et al.2004).

Type

Brazil: Rio de Janeiro, Arraial do Cabo, Ilha do Cabo Frio, ponta do Maramutá, 23°01′S, 42°03′W, 1 m, 21 Dec. 2006, M. D. M. Vianna Filho 1450, R. J. V. Alves 6330 (holotypus R!; isotypi RB!, GUA!).

Morphology General Habit

Perennial, terrestrial, monoecious, saxicolous, fruticose, entirely glabrous herbs up to 25 cm, erect when young, later prostrate, rooting at the base and adventitiously when prostrate

Morphology Branches

Branches fleshy, succulent, prostrate, profusely branched

Morphology Stem

Stem 1 – 2 mm in diam., internodes 2 – 10 mm long, slightly striate, without visible cystoliths

Morphology Leaves

Leaves without any visible trace of stipules, opposite, anisophyllous, with canaliculate, 3 – 6 mm long petioles, lamina obovate to rarely orbicular, fleshy and succulent, 5.0 – 13 × 2.6 – 7 mm, with a rounded to subacute asymmetrical apex, base slightly cuneate to attenuate, asymmetrical; adaxial surface of lamina light green, drying grey to brown, with linear, slightly curved cystoliths; margins entire, slightly revolute, primary nerves pinnate with 2 – 3 secondary pairs

Ecology

Native populations of Pileacarautae are abundant as saxicolous on nepheline syenite outcrops or terrestrial on slopes, from sea level to c. 150 m a.s.l., on hilltops with xeric vegetation typical of the Cabo Frio Diversity Centre. This species often grows on slopes with a highly saline substrate. Within its restricted range, P. carautae was also collected in fissures of a stone bridge (D. Sucre 1528). On Cabo Frio Island, it prefers open xeric vegetation and was also collected on the walls of the old lighthouse at 395 m (Vianna Filho 1230 & T. T. Carrijo). P. carautae was observed on two more islands in the vicinity of Cabo Frio, Ilha dos Franceses and Ilha dos Porcos (Nilber Silva, pers. comm.), and in coastal strand vegetation in the same area, although no voucher specimens are available from these localities.

Conservation

According to IUCN (2001) Red List criteria, this species is considered critically endangered — CR (B1abi.ii) because its known distribution is estimated to be less than 100 km², restricted to the Cabo Frio region.

Note

The species name honours Dr Jorge Pedro Pereira Carauta, Associate Professor, Museu Nacional of Rio de Janeiro, who has dedicated a lifetime of research to the Brazilian species of Urticales. In cultivation, the exposed plants relied on rainwater, while the ones kept inside were abundantly watered. Apart from the expected relatively longer internodes and faster growth of the shaded individuals, which also developed darker green leaves, Pileacarautae retained its differential characters. Unlike the cultivated plants of P. microphylla, those of P. carautae, kept under both conditions, died after several months, first shedding all leaves, then suffering necrosis beginning with the internodes. The difficulties encountered during ex situ cultivation of P. carautae emphasise the importance of conserving the specialised xerophilous vegetation restricted to the Cabo Frio vicinity. However, as long as the Brazilian Navy continues to guard Cabo Frio Island from economic activities, this locality will remain a safe haven for P. carautae and several other rare, endemic and/or endangered species. From the available collections, the distributions of Pileamicrophylla and P. carautae do not overlap, as P. carautae is known only from the Cabo Frio micro-region while P. microphylla is widespread but has not been registered in the range of the former. Common characters of both Pileacarautae and P. microphylla are the prostrate habit, cystoliths in the adaxial leaf epidermis, anisophyllous leaves, pistillate inflorescences subsessile to very shortly pedunculate (peduncles much shorter than the petioles) and pistillate flowers with one perianth segment longer than the others. However, P. carautae differs from P. microphylla by its fruticose habit with opposite branches, fleshy stem, larger, absence of stipules, fleshy and succulent leaves (5.0 – 13.0 × 2.6 – 7.0 mm) with a honey-combed abaxial surface, and by longer staminate inflorescences (5.0 – 10.0 mm long). In herbaria P. carautae is sometimes confused with P. trianthemoides from which it can be distinguished by the anisophyllous leaves with cystoliths in the adaxial epidermis, fragile, herbaceous and fleshy stems, lack of stipules, larger stature, and by being entirely glabrous.