Spirotheca zapotillana Armijos, D. P. González & Nole, 2025

Armijos-Barros, Jorge, González-Sánchez, Diego, Nole-Nole, Darío, Markesteijn, Lars, Escudero, Adrián, Jara-Guerrero, Andrea & Espinosa, Carlos Iván, 2025, A new tree species from seasonally dry tropical forest in southern Ecuador, Spirotheca zapotillana sp. nov. (Malvaceae), resolves a putatively disjunct distribution, PhytoKeys 265, pp. 181-192 : 181-192

Spirotheca zapotillana Armijos, D. P. González & Nole sp. nov.

Fig. 2 , Suppl. material 3.

Diagnosis.

Spirotheca zapotillana Armijos, D. P. González & Nole differs from Spirotheca elegans Carv. - Sobr. et al. in having larger leaflets 35–90 × 15–35 mm ( vs. 20–45 × 8–20 mm) with acute apices ( vs. slightly retuse, obtuse, or acuminate, often mucronate), petiolules 0.9–3.8 mm long ( vs. absent); flowers erect ( vs. slanting downwards) and reddish ( vs. greenish-yellow, then becoming white), staminal tubes non-articulate ( vs. doubly articulate); capsules oblong ( vs. obovoid or rarely spheroid), with brown ( vs. white) kapok.

Type.

Ecuador. Loja. • Zapotillo Cantón: Parroquia Mangahurco , 4°8'30.52"S, 80°25'32.87"W, 473 m, 15 Jan 2025, J. Armijos, D. González & D. Nole 3445 ( holotype: HUTPL 15354 !; isotype: LOJA!; QCNE!) .

Description.

Tree up to 15 m tall, typically found in clumps, some individuals producing clonal offshoots originating from the roots of mature trees, leafless during flowering. Trunks erect, densely covered by conical prickles, 8–33 mm long, 8–23 mm diam. at the base; bark grayish with pale, longitudinal striations; twigs with prickles. Terminal shoots covered by broadly triangular, concave cataphylls. Leaves palmately compound, clustered at branch apices. Petioles 50–100 mm long, 1–1.9 mm diam., slightly pulvinate. Leaflets (5 –) 7 per leaf, 35–90 × 15–35 mm, elliptical, bases cuneate, margins entire, apices acute; petiolules 0.9–3.8 mm long; adaxial surface glabrous and lustrous; abaxial surface glabrous with sparsely pubescent midrib, secondary veins prominent. Stipules linear, caducous, 4.5–12 × 0.9–1.2 mm. Cymes bearing 3–5 flowers, terminal. Flower buds 24–40 × 6–9.5 mm, linear-oblong, green to red prior to anthesis, anthers spirally arranged within the flower buds. Flowers with erect pedicels 13.5–26.1 mm long; receptacles with 4–5 small, conspicuous glands at the base. Calyces 3.5–8 × 6.5–11.2 mm, cupuliform, glabrous externally, sericeous internally, conspicuously 5 - apiculate. Petals 44–52 × 9.5–12 mm, fleshy, oblong, longitudinally asymmetric, reflexed, entirely bright red, densely pubescent internally, externally pubescent on the overlapped portion of petals during the bud stage, sparsely pubescent on the non-overlapped portion. Staminal tube s 25–32 × 2.5–3.4 mm, of uniform width, not articulate, sparsely covered with scaly trichomes; at apex divided into 5 free, reddish filament-like lobes, each 6–9 mm long. Anthers with two pairs of bisporangiate thecae joined at their ends, 14–18 mm long, extrorse, five in number; upper thecae 7–9 mm long; lower thecae 5–8 mm long. Ovaries 5.7 × 2.8 mm, greenish, conical, densely pubescent, 5 - locular. Styles 14–20.5 mm long, slender, declinate at anthesis; stigmas 5 - branched. Capsules 65–80 × 13–15.5 mm, 5 - ribbed, 5 - valved, oblong, apex rounded, containing abundant brown kapok. Seeds 5 × 3.5 mm when mature, reniform, brown.

Additional specimens examined.

Ecuador. El Oro: • [ Las Lajas cantón], Puyango and vicinity , 300–900 m elev., Agu. 1978, D. C. Daly 71 ( NY [05154227 as image!]) . Loja: • Zapotillo cantón, La Manga , 4°13'42.54"S, 80°18'31.23"W, 479 m elev., 16 May 2025, J. L. Armijos Barros et al. 3443 ( HUTPL [15352]!) ; • Ibid., 4°13'44.38"S, 80°17'51.13"W, 473 m elev., 16 May 2025, J. L. Armijos Barros et al. 3444 ( HUTPL [15353]!) ; • Mangahurco , 4°7'49.11"S, 80°25'30.87"W, 496 m elev., 16 May 2025, J. L. Armijos Barros et al. 3446 ( HUTPL [15355]!) ; • Baño del Inca , 4°7'25.83"S, 80°24'26.98"W, 463 m elev., 16 May 2025, J. L. Armijos Barros et al. 3447 ( HUTPL [15356]!) ; • Ibid., 4°7'26.33"S, 80°24'26.87"W, 464 m elev., 16 May 2025, J. L. Armijos Barros et al. 3448 ( HUTPL [15357]!) .

Etymology.

The specific epithet refers to Zapotillo Cantón, southern Ecuador. We chose this name because the majority of documented populations of Spirotheca zapotillana occur in this area. In addition, this area comprises one of the last intact remnants of Ecuador’s seasonally dry tropical forest habitat, a highly threatened ecosystem vulnerable to degradation and fragmentation.

Distribution and habitat.

The species is currently known from four populations within the SDTF of Zapotillo Cantón of Loja Province (at 450–600 m elevations) and one unstudied population in Las Lajas Cantón of El Oro Province (somewhere between 300 and 900 m). Each of the Zapotillo populations contains an average of seven individuals. Mature individuals grow in clumps; some are typically associated with three or more clonal offshoots. These populations occur on rocky hillsides, across a relatively extensive area in deciduous and semi-deciduous forest types characterized by pronounced seasonality (Fig. 3 ).

Phenology.

Spirotheca zapotillana produces leaves at the onset of the rainy season (from January to May). Leaf senescence occurs at the end of the rainy period, and bud formation and flowering begin between June and July. Flowers are present from July to October, and fruiting occurs from September to October.

Preliminary conservation status.

Considering the populations reported in this study, the estimated area of occupancy ( AOO) of Spirotheca zapotillana is restricted to 52 km 2, and its extent of occurrence ( EOO) is approximately 660 km 2. Based on these metrics, S. zapotillana qualifies as Endangered ( EN) under the IUCN Red List criteria B 1 ab (iii, v) + 2 ab (iii, v) ( IUCN 2024). However, it is likely that additional populations occur in unsurveyed areas of tropical dry forests in the Equatorial Pacific region, including across the Peruvian border; thus, the species’ full distribution range may be more extensive than currently known.

The populations identified to date are located in areas subject to intense livestock pressure. Notably, no seedlings or saplings of Spirotheca zapotillana were recorded during monitoring conducted between 2022 and 2025. These results highlight the need for urgent conservation measures, including (1) expanded surveys to determine the species’ actual distribution and (2) the immediate implementation of conservation strategies for the known populations.

Discussion.

The strict consensus tree resulting from maximum parsimony analysis of morphological characters (Fig. 4 ) suggests that Spirotheca zapotillana is sister to S. elegans , with high bootstrap support (BS = 1.0) due to the strong morphological similarity of these two species. This clade was nested within a moderately supported group (BS = 0.67) that also included S. rivieri .

S. zapotillana differs from S. elegans (Table 1 ) in having cymes of 3–5 flowers ( vs. 1–3 flowers). The petals are uniformly reddish ( vs. initially greenish-yellow, later turning white), with the inner surface densely pubescent and the outer surface pubescent only on the overlapped portion ( vs. minutely and densely pubescent on both surfaces). The staminal tube is cylindrical, with scaly trichomes ( vs. doubly swollen with tufted trichomes, becoming glabrous at the apex). The fruit is an oblong capsule ( vs. obovoid or spheroid) that contains brown kapok ( vs. white kapok) and reniform seeds ( vs. pyriform).

S. zapotillana resembles S. rivieri (Table 1 ) in having reddish flowers and a trunk covered with conical prickles. In contrast, it differs in habit, being strictly tree-like, up to 15 m tall ( vs. hemiepiphytic shrubs with a strangler habit or trees 20–30 m tall derived from them). The leaves bear (5 –) 7 leaflets ( vs. 3–7), with elliptical laminae ( vs. elliptic-oblong to elliptic-obovate) and an acute apex ( vs. obtuse and emarginate apex). Calyces are 5 – apiculate ( vs. truncate). The staminal tube is non-articulate ( vs. articulate or not) with sparse, scaly trichomes ( vs. densely tomentose at the base, sparse distally). The style is glabrous ( vs. densely hairy). Capsules are oblong, 65–80 mm long ( vs. elliptic, up to 90 mm).

In 1978, a leafless specimen of Spirotheca ( Daly 71) was collected from the SDTF of southernmost El Oro province. Although its floral characteristics closely resembled those of S. rivieri var. rivieri , the location in Ecuador was strikingly disjunct from that species’ known range in southeastern Brazil. Gibbs and Alverson (2006) noted this specimen as an unresolved anomaly within the genus. Our study concludes that this mystery specimen represents S. zapotillana . We look forward to a molecular study that can resolve whether our new species is in fact most closely related to a species in Brazil or if the morphological similarities (Fig. 4 ) are due to convergence in dry forest habitats.

Figures

Figure 2. Spirotheca zapotillana. A. Branch with leaves; B, C. Mature and young trunk; D. Prickles; E. Cataphylls and stipules; F. Mature leaf; G. Abaxial leaflet surface; H. Cyme; I, J. Front and side views of the flower; K. Denticulate calyx and glandular receptacle; L. Petal; M. Petal with imbricate proportion pubescent (when dry); N. Arrangement of anthers prior to anthesis; O. Thecae; P. Sericeous indument inside the calyx; Q. Conical ovary; R. Longitudinal and transverse sections of the ovary (when dry); S. Fruit with ferruginous kapok; T. Seeds. Lankester Composite Digital Plate (LCDP) comprised of vouchers: A – G. Images from J. Armijos et al. 3443, H – Q. Images from J. Armijos et al. 3445, S, T. Images from J. Armijos et al. 3444.

Figure 3. Spirotheca zapotillana. A, B. Individuals observed growing in clumps at the La Manga locality (wet season); C. Individuals associated with three or more clonal offshoots at the Mangahurco locality (dry season).

Figure 4. Maximum parsimony tree based on morphological characters of Spirotheca species. Bootstrap support values (1000 replicates) are shown below the branches. The analysis was performed using unordered multistate characters; the tree was inferred from a neighbor-joining starting topology and optimized under a parsimony criterion. Species distribution ranges are given in parentheses.