Costus convexus Maas & D.Skinner, 2023

Maas, Paul J. M., Maas-van de Kamer, Hiltje, Andre, Thiago, Skinner, David, Valderrama, Eugenio & Specht, Chelsea D., 2023, Eighteen new species of Neotropical Costaceae (Zingiberales), PhytoKeys 222, pp. 75-127 : 75

Costus convexus Maas & D.Skinner sp. nov.

Diagnosis.

Costus convexus sp. nov. (Fig. 10 ) shares with C. glaucus Maas the presence of glaucous shoots and leaves especially in young plants, but differs from that species by a globose inflorescence enveloped by the upper leaves and by the presence of distinctly convex bracts.

Type.

Colombia, Putumayo: 15 km S of Villagarzón on road to Puerto Umbria, 360 m, 17 Jul 2018, Maas, Maas-van de Kamer , Valderrama, Specht, Erkens & Rodriguez 10707 (holotype. L, 2 sheets) .

Description.

Herb 3-5 m tall, young shoots and young leaves glaucous. Leaves sheaths ca. 20 mm diam; ligule truncate to obliquely truncate, 20-45 mm long; petiole 20-22 mm long, blushed in pink; sheaths, ligule and petiole glabrous; lamina narrowly elliptic, 31- 57 × 12-16 cm, adaxially pale green and glabrous, abaxially green or purple in very young plants, glabrous to sparsely puberulous, base acute to slightly cordate, apex acuminate (acumen ca. 15 mm long). Inflorescence globose to ovoid, 8-20 × 5-8 cm, wrapped tightly by the upper leaves, terminating a leafy shoot; bracts, bracteole, calyx, ovary, and capsule glabrous. Flowers adaxially oriented to erect; bracts distinctly convex, reddish on the outer margins, greenish at the centre, coriaceous, ovate, 55-65 × 40-45 mm, apex obtuse, callus green, indistinct; bracteole boat-shaped, 40-45 mm long; calyx red, 15-25 mm long, lobes shallowly triangular to deltate, 4-10 mm long; corolla deep pink, 80-85 mm long, glabrous, lobes 50-60 mm long; labellum yellow, distal edge horizontally spreading, broadly obovate, 60-70 × 60-70 mm, lateral lobes strongly striped with pink or red, middle lobe reflexed, with yellow honey mark, margin irregularly dentate to lobulate; stamen dark pink, 30-40 × 12-15 mm, not exceeding the labellum, apex obtuse, anther 12-15 mm long. Capsule ellipsoid, 12-30 mm long.

Distribution.

Colombia (Putumayo), Ecuador (Morona-Santiago, Zamora-Chinchipe) (Fig. 21H ).

Habitat and ecology.

In forests, in open shade or sunny areas, often found along roadsides and other disturbed areas, at elevations of 360-1500 m. Flowering year-round.

Etymology.

Costus convexus sp. nov. is named for the form of the bracts, which are distinctly convex; thus, the epithet convexus, an adjective meaning "convex or curved outwards" in Latin.

Paratypes.

Colombia. Putumayo: road to Pto. Guzmán, 300 m, Skinner R3467. Ecuador. Morona-Santiago: near Mendez, 856 m, 17 Oct 2009, Skinner R3196. Zamora-Chinchipe: Zamora-Loja road, 1200-1500 m. 3 Feb 1990, Madsen & Knudsen 86796 (AAU, QCNE); Quebrada del León, affluent of Río Bombuscara, S of Zamora, 1100 m, 5 Feb 1989, Ø llgaard et al. 90385 (AAU, MO), near entrance to P. N. Podocarpus, 970 m, Skinner R3331.

Notes.

Plants of Costus convexus sp. nov. can grow to be huge plants, up to 5 m tall, with large inflorescences and flowers. The younger shoots and leaves usually have a glaucous covering making them appear similar to C. glaucus Maas but having an inflorescence with distinctly convex bracts that are reddish or pink instead of the pale green and glaucous bracts in C. glaucus . It is also characterized by having upper leaves that wrap tightly around and, in doing so, completely hide the young inflorescence.

This new species is observed to be very common along the eastern flanks of the mountains from Putumayo, Colombia, south through Ecuador to Zamora-Chinchipe. Many more recent observations of this new species are recorded on iNaturalist.com in Napo and Pastaza, Ecuador.

Figures

Figure 10. Costus convexus Maas & D. Skinner A plant in habitat with Eugenio Valderrama (left) and Chelsea Specht (right) B inflorescence C inflorescence with scale D upper leaves wrapping around and hiding the inflorescence E close-up of inflorescence F bract (left) and flower (right) detail. Photo in A taken in the wild prior to pressing Maas 10707, Putumayo, Colombia B, C plant observed in Putumayo, Colombia D-F plant observed in Zamora-Chinchipe, Ecuador. Photo A by Paul Maas B-F by Dave Skinner.

Figure 21. Distribution maps for new species of Costaceae: Chamaecostus - Costus douglasdalyi A Chamaecostus manausensis Maas & H. Maas B Costus alfredoi Maas & H. Maas C Costus alleniopsis Maas & D. Skinner D Costus alticolus Maas & H. Maas E Costus antioquiensis Maas & H. Maas F Costus callosus Maas & H. Maas G Costus cochabambae Maas & H. Maas H Costus convexus Maas & D. Skinner I Costus douglasdalyi Maas & H. Maas.