Monstera titanum Croat, M.Cedeño & O.Ortiz, Webbia

Croat, Thomas B., Cedeño-Fonseca, Marco & Ortiz, Orlando O., 2024, Revision of Monstera (Araceae: Monsteroideae) of Central America, Phytotaxa 656 (1), pp. 1-197 : 178-181

50. Monstera titanum Croat, M.Cedeño & O.Ortiz, Webbia 76(2): 275–278. 2021. ( Figs. 86 , 87 )

Type: — PANAMA. Panamá, Antón, El Valle. Valle de Antón, camino a Altos del María , 1030 m, 26 Mar. 2021, M. Cedeño, O. Ortíz, J.E Jiménez & M. Mittermeier 2385 (holotype PMA!, isotype USJ!, MO!) .

Robust to very robust nomadic vine, appressed-climbing habit. SEEDLINGS: bearing foliose leaves. JUVENILE PLANTS: root climbers; stems smooth, dark or light green, sometimes with white dots, cylindrical; internodes 5– 15 cm long, 0.5–1.0 cm diam.; petiole distinct, dark or light green, sometimes with white dots, smooth, 10–25 cm long, sheathed to base of the geniculum; petiole sheath slightly persistent or completely deciduous; leaf blades with collective veins visible, obovate, subcordate to truncate at base, acuminate at apex, thinly coriaceous, 10–20 × 8–13 cm, not appressed to the phorophyte, fenestrations absent or present, arranged on both sides of the midrib and in a single row of small ellipsoid perforations, 2.0– 2.7 mm long. ADULT PLANTS: root climbers; stems light or dark green, white-spotted, smooth or slightly verrucose, cylindrical; internodes 1.5–3.0 cm long, 2–10 cm diam., 0.3–0.7 times as long as wide; anchor roots black; feeder roots black; petiole light green, white-spotted, smooth or verrucose at base, 50–95 cm long, sheathed to base of the geniculum or 15 cm before; petiole sheath slightly persistent; geniculum smooth, sunken adaxially, convex abaxially, 2.0– 4.5 cm long; leaf blades narrowly ovate-elliptic, subcordate at base, acuminate at apex, subcoriaceous to coriaceous, drying dark brown and semiglossy adaxially, greenish yellow to brown abaxially, 47–100 × 28–35 cm, 1.6–1.7 times longer than wide, decurrent on geniculum (decurrent portion 1–2 mm wide); midrib flattened adaxially, convex abaxially, drying reddish, light brown or black on both surfaces; primary lateral veins 20–40 per side, strongly sunken adaxially and prominent abaxially, departing midrib at 75–95°, drying reddish, black or light brown; secondary veins parallel and reticulate toward the margin, undulate when dry; collective veins prominent; fenestrations absent or present in two or three rows, the first row along the midrib, with small perforations of 0.5–5.5 × 0.5–3.5 cm, the second and third rows near the margins, with larger perforations of 9.0–14.5 × 1.7–3.0 cm; margins entire. INFLORESCENCES on ascending stems, very large; peduncle smooth, 25–48 cm long; spathe acuminate, coriaceous, completely open, light green during development, creamy or white externally and white or creamy internally at anthesis, 16.5–47.0 × 10–20 cm, up to 10 cm longer than the spadix; spadix cream at anthesis, 18–24 cm long, 2.5–6.0 cm diam., 5.5–7.3 longer than wide; basal sterile flowers 4–5 mm long; fertile flowers 7–9 mm long; stamens 3–8 mm long, with laminar filaments; anthers 1.5–2.0 mm long; ovary rectangular in longitudinal section, ribbed, 5–6 × 2–3 mm; style hexagonal, 4–5 × 2.5–3.0 mm; stigmatophore slightly conical, 1.5–2.0 mm long; stigma circular; berries with a creamy stylar cap during development, ripe berries color unknown; seeds unknown.

Distribution and ecology: — Monstera titanum is endemic to Panama, where it is known from the type locality on Altos del Maria, Valle of Anton, and the border of Chiriquí and Bocas del Toro Provinces (Fortuna), at 1450–1480 m elevation in Premontane rain forest life zones.

Phenology: —Flowering in January, March and November. Fruiting in March, June and November.

Discussion: —The species, a member of sect. Monstera , is characterized by its juvenile plants with narrowly ovate, often perforated leaves and adult plants growing as nomadic vines with an appressed-climbing habit, stems with short internodes, densely speckled, fully sheathed petioles with a sharply sulcate geniculum, large, narrowly ovate-elliptic, subcordate leaf blades with two rows of small elliptic fenestrations on both sides and drying pale greenish yellow-brown on the lower surface. The inflorescence is remarkable for its extraordinary size, with the peduncle and whitish, long acuminate spathe each up to almost half a meter long in very robust individuals. The spadix was often found eaten by beetles but with the spathe still intact. This is unusual as typically the spathes are much more ephemeral than the spadices. Monstera titanum is similar to M. alfaroi (Cedeño et al. 2020e) , but differs in having smooth, light green and white-spotted petioles (vs. black-warty, light green and light brown petioles), cordate leaf-blades (vs. rounded at base), and smooth (vs. warty) peduncles ( Cedeño-Fonseca et al. 2022).

The populations of M. titanum from Fortuna need more widespread fieldwork in order to document the inflorescence, spathe and shape of the flowers. Only once has it been possible to collect this species in Fortuna with infructescence. This was during fieldwork in 2018. We never saw the inflorescence in development or anthesis, but the leaves and the stems are very similar to the population from Valle de Antón.

Additional specimens examined: — PANAMA. Bocas del Toro: Cerro Colorado , 9.2 miles W of Chamé; along trail E of road which leads down to stream, 1450–1480 m, T.B. Croat 69033 ( MO!) ; Cerro Colorado, along road between Río San Felix and mining exploration camp, 7 mi W of Chamé, along trail through Guaymí village , 1500 m, T.B. Croat 69190 ( MO!) ; Bocas del Toro –Chiriquí border, Fortuna Dam region , along continental divide trail, 1200 m, G. McPherson 13548 ( G, MO, NY) ; Chiriquí: Cerro Colorado, along mining road, 31.6 km beyond bridge over Río San Félix (10.6 km beyond turnoff to Escopeta), 1690 m, T.B. Croat 37178 ( MO!) ; Fortuna, Hornito, Along the road to the Fortuna Dam site, N of Gualaca, 22.7 mi beyond the bridge over the Río Estí, 11.8 mi N of Los Planes de Hornito, 10.7 mi N of jct. to tunnel, 1400 m, T.B. Croat 48691 ( MO!) ; Along road between Fortuna Lake and Chiriquí Grande; 4.5–5 km N of dam over Fortuna Lake, 1100–1135 m, T.B. Croat 60003 ( MO!) ; Cerro Colorado, along road to old copper mine development N of San Félix, 18.6 mi N of bridge over river near San Félix, 6.6 mi beyond Chamé and road to Escopeta, 1475–1485 m, T.B. Croat 75008 ( MO!) ; Cerro Colorado, along road to copper mine development N of San Félix, 20.5 mi N of the bridge near San Félix, 8.3 mi beyond Chamé and turnoff to Escopeta, 1630 m, T.B. Croat 75026 ( MO!) ; Gualaca, Reserva Forestal Fortuna . División Continental, 1154 m, O. Ortiz et al. 1809 ( MO!, PMA!) ; Gualaca, Corregimiento Hornito, Reserva Forestal Fortuna, senderos cerca al centro de investigaciones Jorge L. Arauz, 1200–1500 m, A. Zuluaga 914 ( PMA!, MO!, WIS!) ; Ngäbe-Buglé (Bocas del Toro): Cerro Colorado , 9.2 mi W of Chamé, along trail E of road which leads down to a stream, 1450–1480 m, 6 Jul 1988, T.B. Croat 69012 ( MO!, PMA!) ; Chiriquí, Gualaca, Hornito. Fortuna, camino a Chiriquí Grande, 1230 m, M. Cedeño et al. 2329 ( PAM, USJ) .

Figures

FIGURE 86. Monstera titanum from Panama. (A) Developing inflorescence. (B & C) Front and back views of open inflorescence. (D) Fertile flower in lateral view (left) and longitudinal section (right). (E) Stylar plate top view (left), and individual stamen (right). (F) Sterile flower in lateral view (left) and longitudinal section (right). (G) Adult plant. M. Cedeño et al. 2385 (PMA). Image from Cedeño-Fonseca et al. (2020b).

FIGURE 87. Monstera titanum from Panama. Adult plant growing in the locality type. M. Cedeño et al. 2385 (PMA). Image from Cedeño-Fonseca et al. (2020b).