Monstera guzmanjacobiae Díaz Jiménez, M.Cedeño, Zuluaga & Aguilar-Rodríguez, 2020

Jiménez, Pedro Díaz, Aguilar-Rodríguez, Pedro A., Cedeño-Fonseca, Marco, Zuluaga, Alejandro, Croat, Thomas B., Montano, Martin Alarcón, Jiménez-Segura, Mario, López-Mora, Marco, Macswiney, M. Cristina & Yovel, Yossi, 2020, Monstera guzmanjacobiae (Araceae), a new species from Mexico with notes on its reproductive biology, Phytotaxa 437 (1), pp. 39-46 : 41-44

Monstera guzmanjacobiae Díaz Jiménez, M.Cedeño, Zuluaga & Aguilar-Rodríguez , sp. nov. ( Figs. 2–4 ).

Monstera guzmanjacobiae can be confused with the endemic Costa Rica species Monstera luteynii Madison and Monstera maderaverde Grayum & Karney from Honduras. However, in these species, the leaf blades are two to three times smaller and lack fenestrations (rarely present in M. maderaverde ), and the flowers have truncate styles (vs. pyramidal and conical in M. guzmanjacobiae ). In M. guzmanjacobiae , the yellowish coloration of the aril is unique and represents first record for the genus and for sect. Marcgraviopsis .

Type: — MEXICO. Veracruz: Municipio Catemaco, La Palma, Selva alta perennifolia, 18º33’21’’N, 95º03’35’’W, 56 m, 31 May 2014, Pedro Díaz Jiménez & Valeria Guzmán Jacob 1305 (holotype XAL!, isotypes, MEXU!, UJAT!).

Hemiepiphytic herb, 1–25 m above the ground, stems appressed-climbing and ultimately pendent. SEEDLING: terrestrial, filiform. JUVENILE PLANT: stem terete, light-green, smooth, dorsiventrally compressed, internodes 4–8 cm long, 3–5 mm diam. Leaves completely adhering to surface of phorophyte; petiole not visible, 1.0– 2.5 cm long; blade 6–9 × 5–8 cm, coriaceous, obovate, without fenestrations, occasionally with white spots abaxially, base cordate, apex short-acuminate. ADULT PLANT: anchor roots brown; feeder roots light beige, suberous, up to 35 cm long; internodes 6–12 cm de long, 0.8–2.5 cm diam., dark green, semiglossy, scaly or with a clear brown cuticle, thin, exfoliating, with few greenish pustules, rarely smooth, sulcate on one side; leaves erect or pendent; petiole opaque green, 15–25 (–30) cm long, glaucous and striated at the base, slightly white spots, smooth to geniculum, sheathed up to 1.5 cm before or to the base of geniculum; sheath marcescent, remanents as fibers, apical ligule 1.5–3.0 cm de long; geniculum 0.5–3.5 cm long, 0.4–1.0 cm diam., light green or dark, smooth or striate, terete; blade 18–59 x 15–37(–40) cm, ovate to widely elliptic, chartaceous or thinly coriaceous, cordate to semi-cordate at base, acute or acuminate at apex, dark green and glossy on the upper surface, bright light green on the lower surface, drying light brown on the upper surface, matte green on the lower surface; fenestrations usually only on one side, perforations 1–4, oblong-elliptic, margins blade entire; midrib sunken above, prominent below; primary lateral veins 5–9 per side, raised on the lower surface, whitish; tertiary veins parallel, connected near the middle of the blade up to margin. Inflorescence axillary, often solitary, rarely 2 per axil, rarely erect, inclined between 40–60°, on appressed-climbing or pendent stems; peduncle 5–20 cm long, 0.8–2.0 cm diam., green or yellowish, smooth to the apex, with greenish and white pustules at the base; spathe 15–19 × 12–15 cm, green prior to anthesis, at anthesis yellowish externally and white to creamy internally, coriaceous, cucullate, obtuse or mucronate at the apex, marcescent after anthesis, up to 1 cm longer than spadix and not enclosing it; spadix 8–16 cm long, 2–4 cm diam., white when immature, white-cream at anthesis; basal region of sterile flowers up to 2 cm in long, not decurrent on peduncle, tapering basally; flowers 5–7 mm long; ovary 4–5 × 3.5–4.0 mm, square and ribbed in longitudinal-section; style 3.5–4.0 mm long, 2.5–3.5 mm wide, pyramidal and conical, stigma linear, stigmatic secretion yellowish; stamens 1–6 mm long, filament laminar, anther 1.5–2.0 mm long; sterile flowers 4–6 mm long, with yellowish secretion. Infructescence with stylar cap green after anthesis, yellowish green at maturity; fruits with white pulp; seeds 6–9 × 5–7 mm, pale brown, with yellowish aril, ovate-oblong; hypocotyl thick and yellow.

Distribution, habitat and conservation status: — Monstera guzmanjacobiae is endemic to the Los Tuxtlas region, Mexico. It is known from the municipality of Catemaco between La Palma and the road between Tebanca and Miguel Hidalgo, at elevations from sea level to 400 m, in high evergreen rainforest, edge and the interior of the forest, as well as in live tree fences and in abandoned areas of secondary vegetation (locally known as “acahuales”). According to the IUCN Red List Categories and Criteria, the species is considered in CR and EN.

Phenology: —Flowering and fruiting was recorded in February, March, April, May, June and November.

Floral ecology and reproductive biology: —At the beginning of the flowering sequence (female phase), the spathe unfolds slightly, creating a chamber between the spathe and the spadix with a narrow opening that forms when the edge of the spathe peels away ( Fig. 4D ). At the base, a second access to the flowers is created when a small hole is opened. At this time, the stigmas of the sterile flowers secrete a sticky transparent resin and emit a strong fruity odor (similar to “that of ripe melon”). The stigmas of all the flowers become receptive when they secrete a transparent to slightly yellowish fluid. In the hours or days that follow, the spathe continues inflating and gradually, expanding its opening. Before anthesis ends, the stigmas wither, the anthers emerge and the pollen is released, and then the spathe opens completely. Small insects, nitidulid beetles and drosophilid flies have been observed inside the floral chamber, and male euglossine bees ( Euglossa sp. ) flying and walking outside the spathe ( Fig. 4D ). According to the flowering behavior of the inflorescence and to that documented in other Monstera species ( Chouteau et al. 2007; Prieto & Cascante-Marín 2017), it is possible that only beetles and flies are their pollinators. Once the fruits mature, a large number of ants of the genus Acromyrmex sp. visit the infructescences, apparently to feed on the white pulp that covers the seeds ( Figs. 4B, C ).

Eponymy: —The species is named in honor of Mexican biologist Valeria Guzmán Jacob from the Göttingen University, who helped to collect the type specimen.

Additional specimens examined (paratypes):— MEXICO. Veracruz: Municipio Catemaco, La Palma, Acahual (con elementos de selva alta perennifolia), 18º33’12’’N, 95º03’41’’W, 30 m, 20 September 2018, Pedro Díaz Jiménez, P. Adrián Aguilar Rodríguez & M. Montano Alarcón 1427 ( MEXU; UJAT) ; Municipio Catemaco, Tebanca, relicto de selva alta perennifolia, 18º22’13’’N, 95º00’56’’W, 361 m, 25 February 2019, Pedro Díaz Jiménez & M. Montano Alarcón 1429 ( XAL) .

Notes: —In Los Tuxtlas region, although one of the most studied sites in Mexico ( Guevara et al. 2004), M. guzmanjacobiae had not been previously collected. This new species differs from others in the genus by the ligule of the petiole sheath 1.5–3 cm in length, the adult leaf blade with fenestrations (1–4 perforations) often only on one side or lacking fenestrations, the inflorescence erect or inclined, the flowers with a conical pyramidal style, the seeds with a yellowish aril and with a thick yellow hypocotyl. A unique feature in M. guzmanjacobiae is the yellowish coloration of the seed aril and the thick, yellow hypocotyl.

Monstera guzmanjacobiae is the third species of Monstera in Mexico reported to have a flowering on pendent stems and the fourth within sect. Marcgraviopsis . Although is similar to M. luteynii Madison (1977: 207) and M. maderaverde Grayum & Karney (2012: 66) , endemic species from Costa Rica and Honduras respectively, both species have non-fenestrate blades (rarely in M. maderaverde ) and flowers with truncate style. In addition, this last species belongs to sect. Tornelia . The pendent habit also occurs in the Mexican species M. tuberculata Lundell , although the latter has leaf blades two to three times smaller, rarely fenestrate, and the inflorescences are completely pendent (inclined between 40–60° and rarely erect in M. guzmanjacobiae ). Adults plants of M. guzmanjacobiae have leaf blades similar to those of pre-adult M. punctulata . However, in this last species the fenestrations have varied sizes and some reach the edge of the blades.

Figures

FIGURE 2. Monstera guzmanjacobiae sp. nov. A. Young inflorescence; B. Infructescence with stylar caps mostly already detached; C. Complete flower (left) in lateral view showing an immature stamen; gynoecium in longitudinal-section (right); D. Adult plant showing pendent inflorescence and developing flagellum; E. Open inflorescence in ventral view; F. Open inflorescence in dorsal view; G. Sterile flowers, lateral view; H. Style and stigma seen from above (left); immature stamen (right); I. Seed, lateral view; J. Stolon-like seedling transforming into a juvenile shingle-leaved plant at its apex; K. Juvenile plant shingle leaved climbing plant.

FIGURE 3. Monstera guzmanjacobiae sp. nov. A. Habit of plant ascending on a tree to over 25 m; B. Habit of plant pendent from a living fence in a pasture area; C. Scaly pendent stems (i), petiole striate at the base (h); D. Infructescences on ascending stems; E. Young stem showing petioles with glaucous base, marcescent petiolar sheath (m) and apical projecting ligule 1.5 cm long (n); F. Completely terete geniculum; G. Base of the petiole with green and white projections.

FIGURE 4. Monstera guzmanjacobiae sp. nov. A. Detachment stylar layer of a mature infructescence; B and C. Exposed seeds surrounded with white pulp, with numerous foraging ants of the genus Acromyrmex sp.; D. Euglossine bee (Euglossa sp.), visiting the inflorescence at the beginning of the female phase of anthesis.