Pentaplaris Notes

Pentaplaris davidsmithii L.J.Dorr & C.Bayer
Pentaplaris doroteae L.O.Williams & Standley
Pentaplaris huaoranica L.J.Dorr & C.Bayer

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Until recently the genus Pentaplaris was known from a species, Pentaplaris doroteae, described in 1952, endemic to Costa Rica. In 1999 Pentaplaris davidsmithii from Boliva and Peru, and Pentaplaris huaranica, from Ecuador, were added.

Pentaplaris was originally assigned to Tiliaceae (tribe Brownlowieae), but current opinion is that it belongs to either Malvaceae s.s. or Bombacaceae. Current opinion places it in subfamily Malvoideae, and closer to the Eumalvoideae clade (Malveae, Gossypieae, Alyogyne and Hibisceae) than to Matisieae (Matisia, Phragmotheca and Quararibea). The position is supported by its possession of echinate pollen, which is a derived characteristic shared with Eumalvoideae, and by cpDNA sequence data which places it as the sister to all of Malvoideae excepting Matisieae. This implies that unless one except paraphyletic taxa it will be necessary to introduce a tribe Pentaplarideae for this genus. However nrDNA (ITS) data suggests that it is sister to Matisieae.

Species of Pentaplaris are tall, buttressed, trees. The leaves are alternate, petiolate and simple, with entire margins. The stipules are fused, sheathing the petiole, and enclosing the leaf buds. The flowers are borne in paniculate inflorescences. The flowers are hermaphrodite. The epicalyx is fused, enclosing the floral bud. The persistent and accrescent calyx is campanulate; its lobes are imbricate in bud. (Species of Malvaceae almost uniformly have calyces which are valved or reduplicate-valvate in bud.). The staminal column is more or less lobed, apically bearing monothecal anthers on short free filaments. The pollen in echinate. The ovary is 2-locular, with 2 basal-ascendent ovules in each locule. The stigma is discoid-capitate. The fruits are indehiscent, single-seeded by abortion of remaining ovules, and winged by the accressecent sepal lobes. The cotyledons are foliose and more or less folded in the seed.

The known distribution of Pentaplaris doroteae is limited to a small area of Costa Rica (the Palmar Norte region of the Osa peninsula). It is a straight-trunked, gray-barked tree reaching 120 ft in height, the trunk being roughly 30" in diameter, with open, spreading, rather flat-topped crowns. The leaves are ovate-elliptic, shortly acuminate, subcordate, and with a stellate-pubesence on the lower surface. The petiole is thickened and glandular at the apex. The calyx varies in color from pinkish to reddish brown. The petals are connate at the base. The staminal column bears numerous anthers on short free filaments clustered into 5 bundles. The stigma is weakly lobed.

Photographs of P. doroteae are available at Tropicos.

Pentaplaris davidsmithii is found in Peruvian and Bolivian Amazonia. Specific sites include the Cordillera Azul of Peru, and the Madidi catchment of Boliva.

Pentaplaris huaranica is found in the Yasuni National Park and Huaorani reserve of Napo province in Ecuadorian Amazonia. The type specimen is recorded as a 60 ft high tree, with white 5-petalled flowers. It has ovate-acute leaves which are 3-nerved at the base and otherwise pinnately nerved, and which possess entire margins, rounded bases, and acute to acuminate apices. Figures of this species, and P. davidsmithii, are available on the US National Museum of Natural History website. An additional herbarium specimen can be seen at NYBG.

References

  1. Kubitzki & Bayer, in Kubitzki & Bayer, The Families and Genera of Vascular Plants, Vol. 5 (2003)
  2. Hutchinson, The Genera of Flowering Plants (1967)

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© 2002, 2005 Stewart Robert Hinsley