MONSTERA OBLIQUA
PROTOLOGUE: Monstera obliqua Miq., published in Linnaea 18: 79 (1844). The protologue is reproduced below.
SYNONYMS:
HETEROTYPIC SYNONYMS: Heteropsis obliqua Miq. ex Engl.; Monstera expilata Schott; Monstera falcifolia Engl.; Monstera falcifolia var. latifolia K.Krause; Monstera fendleri Engl.; Monstera killipii K.Krause; Monstera microstachys Schott; Monstera obliqua var. expilata (Schott) Engl.; Monstera sagotiana Engl.; Monstera snethlagei K.Krause; Monstera unilatera Rusby
OTHER NAMES: Timbo titica (Brazil, Para); mamurillo (Venezuela)
DISTRIBUTION: Costa Rica to S. Trop. America and Trinidad: Bolivia, Brazil North, Brazil Northeast, Brazil West-Central, Colombia, Costa Rica, Ecuador, French Guiana, Guyana, Panama, Peru, Suriname, Trinidad and Tobago, Venezuela.
DISTRIBUTION NOTE: Colombia: Chocó Trinidad and Tobago: Tobago iNaturalist: Acre, Cochabamba, Loreto, Madre de Dios, Orellana, Sucumbíos, Veraguas.
SPECIES DESCRIPTION:
Nomadic vine, appressed-climbing habit. Seedlings: bearing foliage leaves. Juvenile plants: root climbers; stems smooth, dark green; internodes 3–5 cm long, 2–5 mm diam.; petiole conspicuous, dark green, smooth, 5–11 cm long, sheathing to base of the geniculum; petiole sheath deciduous; blades lanceolate, truncate at base, acuminate at apex, subcoriaceous, 7–13 × 2–4 cm, not appressed to the phorophyte; fenestrations absent. Adult plants: root climbers; stems smooth, light to dark green; internodes 2–10 cm long, 0.3–0.8 mm diam., 10.0–12.5 times longer than wide; cataphylls light-green, deciduous but leaving dry fragments on peduncles; anchor roots black; feeder roots black; petiole light green, smooth, 5–18 cm long, sheathing to the geniculum, petiole sheath deciduous; geniculum smooth, 3–5 mm long; blades lanceolate to narrowly elliptical, cuneate at base, acuminate at apex, membranous to subcoriaceous, drying blackish, reddish, light brown or grayish, 12–23 × 3–10 cm, not decurrent on geniculum; midrib ribbed adaxially, convex abaxially; primary lateral veins 4–8 per side, obscure adaxially, prominent abaxially, departing midrib at 35°–50°; secondary veins inconspicuous; collective veins not visible; fenestrations absent or scarcely developed (in Central America); margins entire.⁴
INFLORESCENCE:
Inflorescences on ascending stems, 1–3 simultaneously at flowering time, arranged in the axils of the leaves or cataphylls; peduncle smooth, 10–17 cm long, 5–6 mm diam.; spathe acuminate, light-green during development, yellow externally and white internally at anthesis, the margins towards the apex involute, deciduous at the end of anthesis, up to 4 cm longer than the spadix; spadix with green style margins and white at the medial part during development, cream at anthesis, 3–5 × 0.5–1.0 cm; basal sterile flowers scarce or absent; fertile flowers 4–7 mm long; stamens 1–2 mm long, with laminar filaments; anthers 1–2 mm long; ovary square in longitudinal section, ribbed, 1.5–2.0 × 1.5–2.0 mm; style square or hexagonal, 1.5–2.0 × 2.5–3.0 mm; stigma linear; berries with a moss-green stylar cap during development, mature stylar cap orange; pulp white; seeds black, 3–5 mm long.⁴
ECOLOGY:
Monstera obliqua ranges from Costa Rica to the Pacific slope and adjacent lowlands of the departments of Chocó and Valle in Colombia, and to Venezuela, the Guianas, and throughout the Amazon basin, at 0–1410 m, in Tropical moist forest, Tropical lower montane wet forest and Montane moist forest life zones. Flowering has been recorded from July to November. Fruiting in January, March July and November.⁴
ETYMOLOGY:
Latin obliqua, "oblique," referring to the oblique leaf bases.⁶
NOTES:
1. The species is a member of sect. Monstera. It differs from the other species of the genus in Costa Rica by its slender petioles (<0.5 cm diam.), sheathed to the base of the geniculum, the entire, narrowly lanceolate, not or hardly fenestrate leaf blade; the infructescence with the stylar layer orange with white pulp beneath. Vegetatively, individuals of Monstera obliqua with fenestrate leaves can be confused with the dry forest morphotype of Monstera adansonii. Another species with which it could be confused is Monstera gambensis, which has the petiole rough, persistent petiolar sheaths with involute wings, and is known only from a collection on the Pacific side in the area of La Gamba, Golfito. In its current conception, Monstera obliqua is a very variable and widespread species, including forms with widely varying and sometimes extreme leaf fenestration patterns, occurring across much of lowland wet tropical South America. It may be that further study will show that it covers several species. There are a number of synonyms based on South American and West Indian representatives which it is beyond the scope of this paper to evaluate (Cedeño-Fonseca et al. 2022).⁴
2. Conservation status: Monstera obliqua is protected in the Refugio de Vida Silvestre Mixto Gandoca-Manzanillo, Reserva Indígena Talamanca Bribri and Reserva Biológica Hitoy Cerere.⁵
STORY:
STORY TITLE: The strict outcrosser
Monstera obliqua is one of only two species in the genus whose pollination has been followed through a full cycle in the wild, in French Guiana.⁷ The inflorescence ran for about 48 hours over three days. Every one of the 242 insects that entered was the same nitidulid beetle, Colopterus amputatus; the beetles arrived on the first two days, packed the chamber behind the spathe, mated there, and left at daybreak on the third day dusted with pollen.⁷ The spadix warmed by only about two degrees above the night air, peaking around one in the morning as the pollen was shed.⁷
All 15 inflorescences bagged before opening aborted within a week, so the species cannot set fruit on its own, and even in the open 20 of 28 inflorescences aborted.⁷ Where pollination succeeded, about 84 percent of the flowers set fruit, with three or four seeds to a berry.⁷ A decade later Monstera lentii in Costa Rica gave the opposite answer: 6 of 11 bagged inflorescences set fruit and none aborted.⁸ Two species in one genus, one strictly outcrossing and one self-compatible, and no way yet to say which is the rule.
The plant grows fast for a Monstera. Tagged stems elongated 2 to 5 m a year and put out 30 to 70 leaves, a rate that suggests flowering within about a year and a half of germination.⁶ The holes in those leaves form early, while the blade is still folded in the bud: at each future perforation a small patch of cells dies on cue while its neighbors go on dividing, and the hole opens as the blade expands around the dead disk.⁹
In the field the species is slender and loosely attached to its host, with a spadix no more than about a centimeter thick, a dull yellow spathe, and every flower fertile to the base; Monstera adansonii is more robust and closely appressed, has sterile basal flowers, and its berries carry a hard stylar cap that falls when they ripen.¹⁰ The ripe infructescence of Monstera obliqua is orange, a color it shares in the genus only with Monstera praetermissa of eastern Brazil and Monstera xanthospatha of the Colombian Andes.¹¹
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Monstera obliqua Miq.
2. Linnaea 18: 79 (1844) — protologue.
3. iNaturalist: Monstera obliqua
10. Gonçalves 2002. Monstera obliqua vs. Monstera adansonii. Aroid-L, 13 February 2002
Additional photos by Patrick Blanc
Additional photos by David Scherberich
Additional photos from iNaturalist by Stéphane Bello, mhomison, Alice Bello, zschulman, Anders Hastings, Ana Maria Benavides, ilyascarre, Jeremy Cowan, Mayra Licuy, nates_, Riley Fortier, roseanny, Ari Rice, Azalia Estefanía Criollo Nuñez, Gino Gajadien, Guillaume Léotard, icedocmo, Joel Tupac Otero Ospina, jordan loftin, Júllyana Fernandes, Leoš Smutný a Antonín Horáček, Linton_Arneaud, Marcos Oliveira, Marcos Silveira, Mike Steinmann, ramon_d, Sami Dolan, SuperMeiTravel and Tucker Hastings
Additional photos from Wikimedia Commons by Mickaël Schauli, Mickaël Schauli, Mickaël Schauli and Mickaël Schauli
