Heisteria austroecuadorica Cornejo, Homeier & C. Ulloa, 2023

Cornejo, Xavier, Homeier, Jürgen & Ulloa, Carmen Ulloa, 2023, Heisteria austroecuadorica (Erythropalaceae): A new species from southeastern Ecuador, Phytotaxa 599 (3), pp. 201-206 : 202-204

Heisteria austroecuadorica Cornejo, Homeier & C. Ulloa sp. nov. ( Fig. 1 ).

Diagnosis: — Species nova affinis Heisteria asplundii , a qua folia angusta, stamina decandra, calycem fructuum basin non occultans differt.

Type: — ECUADOR. Zamora Chinchipe: area of the Reserva San Francisco , 3°58’S 79°04’W, 1980 m, 6 September 2005 (fl, fr), J. Homeier & S. Hänel 1609 (holotype: GUAY!; isotypes: GOET!, LOJA!, QCNE-195572!).

Description: — Tree, to 20 m tall and 30 cm DBH; milky white latex present in stems and branches; branches ca. 2 mm thick, terete, striate, glabrous. Leaves alternate; petiole 7–16 mm long, rugose, light- to dark-brown, channeled above, glabrous; lamina chartaceous, (4.5–)7–19 × 2–6 cm, elliptic-lanceolate to narrowly elliptic or narrowly lanceolate, apex acuminate to long-caudate, drip-tip 7–12 mm long, base cuneate, margins revolute, dull, smooth, and glabrous on both sides, venation brochidodromous, midrib slightly sulcate above, prominent below, secondary nerves 6 to 9 pairs, prominulous, tertiary venation inconspicuous. Inflorescence ramiflorous, a short axillary fascicle, 3 to 15 flowers per fascicle; bracts cucullate-deltoid, 0.5–1 × 0.5–1 mm, the apex obtuse to broadly obtuse; pedicel 5–7 mm long. Calyx patelliform or cup-shaped, 5-lobed, lobes ca. 0.5 mm long, triangular to broadly triangular, acute at apex, green. Petals 5, ca. 3 × 1 mm, free, densely papillose or shortly pilose on the adaxial side, greenish-white. Stamens 10, filaments ligulate, ca. 2 × 0.3 mm, the 5 inner ones ca. 1.8 mm, all free, anthers ca. 0.5 × 0.8 mm. Nectary absent; ovary oblatesubglobose (in vivo), pyriform (in sicco); style ca. 0.5 mm, stigma slightly 3-lobed. Fruiting pedicel 1.5–2.3 cm long, slightly swollen, 2–3 mm distally. Fruiting calyx slightly 5-lobed, 2.2–2.8 cm in diam., reflexed, stiffly chartaceous, orange to red, bright and shiny above, dull below. Drupe barrel-shape, olive green with maroon at apex (in vivo), 1.2–2 × 1–1.2 cm, rugulose, faintly ribbed longitudinally and tuberculate (from endocarp, in sicco), with a clear, deep, circular depression at the apex.

Etymology: —The epithet refers to the geographic pattern of distribution at southeastern Ecuador where the species occurs.

Habitat and distribution: — Heisteria austroecuadorica is known from the San Francisco reserve, a forest remnant close to the settlement of El Líbano north of the Podocarpus National Park, and the Jamboe river basin in southeastern Ecuador, between 1000 to 2050 masl; all three localities are on the Loja-Zamora road. The area is characterized by a rugged terrain and small-scale structural and floristic vegetation changes, which result mainly from the decreasing soil fertility along ravine-slope-ridge gradients (Werner & Homeier 2015). The newly described species is restricted to the ravines and lower slope positions with more fertile soils within the species-rich evergreen lower montane forests below 2050 masl, that reach up to 30 m height ( Homeier et al. 2008, 2010).

In the ravines and on the lower slopes of this specific forest type, Heisteria austroecuadorica is accompanied by several tree species that have been described from this zone in the last years, stressing the biological importance of this area. Some examples are: Byrsonima homeieri Anderson (2007: 97) , Critoniopsis zamorensis Haro-Carrión & Robinson (2008: 17) , Meliosma longepedicellata Cornejo (2009: 93) , Magnolia zamorana Arroyo et al. (2013: 507) , Meriania franciscana Ulloa Ulloa & Homeier (2008: 383) , Naucleopsis francisci Berg & Homeier (2010: 197) , Ocotea homeieri van der Werff (2020: 210) and Quiina zamorensis Schneider & Zizka (2012: 265) . All of these aforementioned species have a narrow pattern of distribution that is restricted to the particularly diverse Amotape-Huancabamba zone ( Weigend 2002, 2004), south of the Girón-Paute dry valley in southern Ecuador ( Jørgensen et al. 1999).

With its relatively high-density wood (0.72 g /cm 3), large fruits and slow diameter growth rates, Heisteria austroecuadorica combines characteristics typical of a late successional tree species.

Phenology: —Flowering was observed in June, September, October and December; fruiting material was collected in April, September and October. There are no existing observations on flower pollination or fruit dispersal.

Conservation status: —This species is uncommon in the Reserva San Francisco: Homeier has only found a total of six trees (out of almost 4000) within three recently established one-hectare plots. At a second location, outside the Reserve, in El Líbano, only one tree has been seen. A third locality is represented by one collection only in the Jamboe river basin just further down at slightly lower elevation. Based on the very small area of occurrence (12 km 2), an extent of occurrence of 10.3 km 2, the existence of only three localities, only one of which is protected within the private Reserva San Francisco, we assign a provisional category of Endangered (EN B2a(iv)), following the IUCN (2022) criteria.

Paratypes: — Ecuador: Zamora Chinchipe: Reserva San Francisco, road Loja-Zamora , ca. 30 km from Loja, 3°58’S 79°04’W, 1800–2050 m, June 2005 (fl.), O. Cabrera & N. León 869 (HUTPL, fragm. in GUAY) ; same location, 1840 m, 20 October 2001 (fr.), J. Homeier 1025 ( LOJA, QCNE, MO, GOET) ; same location, 1910 m, 11 September 2003 (sterile), J. Homeier & W. Quizhpe 1261 ( GOET, MO, QCNE) ; same location, 1910 m, 20 October 2013 (fl.), J. Homeier 5098 ( HUTPL, QCA, GOET) ; same location, 2040 m, 5 December 2016 (fl.), J. Homeier & J. Peña 5820 ( HUTPL, QCA, GOET). Road Loja-Zamora , El Líbano, 4°5’S 78°59’W, 1720 m, April 2011 (fr.), J. Homeier, F.A. Werner & D. Cárate 4713 ( LOJA, QCA, QCNE, GOET). Cuenca del río Jamboe , 4°08’S 78°56’W, 1000 m, September 1999 (fl, fr), W. Palacios 14881 ( MO) .

Discussion: —The fruits of Heisteria austroecuadorica are characterized by the apex presenting a circular depression, a key character in Sleumer’s treatment (1984) that is only found in three other species in tropical America: H. amphoricarpa Sleumer (1984: 49) , H. asplundii , and H. skutchii Sleumer (1984: 50) . Heisteria amphoricarpa , a Brazilian species, has a unique urn-shaped calyx enveloping most of the drupe and flowers with five stamens, while H. skutchii , a Costa Rican species with 10 stamens, has much wider, patent fruiting calyx (over 30 mm diameter). In Ecuador, the fruits of Heisteria austroecuadorica are relatively large with a depressed apex like those of H. asplundii , a tree endemic to northwestern Ecuador. However, H. austroecuadorica immediately differs from H. asplundii by its narrower leaves, with blades elliptic-lanceolate to narrowly elliptic or narrowly lanceolate, 2–6 cm wide (versus leaves always with broadly elliptic blades, 10–15 cm wide in H. asplundii ), the flowers with 10 stamens (vs. 5 stamens), the smaller fruiting calyx, up to 2.8 cm and covering just the base of the drupe (vs. up to 4.8 cm and covering the basal 1/3 of the drupe); additionally, these two species are widely separated on opposite sides of the Andes mountains.

Figures

FIGURE 1. Heisteria austroecuadorica Cornejo, Homeier & C. Ulloa. A, Inflorescence with flower buds. B, Terminal branchlet and immature fruits. C, Fruits surrounded at base by an accrescent persistent reddish-orange calyx. D, Pedicel and abaxial view of fruiting calyx. E, Abaxial view of a leafy branch and immature fruits. Photos by Jürgen Homeier, from the type population.