Four new species of Monstera (Araceae) from Panama, including one with the largest leaves and another with the largest inflorescences in the genus

: Monstera bocatorensis Croat & M.Cedeño, Monstera donosoensis Croat, M.Cedeño & O.Ortiz, Monstera gigas Croat, Zuluaga, M.Cedeño & O.Ortiz, and Monstera titanum Croat, M.Cedeño & O.Ortiz are newly described from Panama, and illustrated from living material.


INTRODUCTION
Monstera Adanson (1763), widespread in the Neotropics, is especially diverse in the Cordillera de Talamanca of Costa Rica and Panama (Madison 1977), principally on the Caribbean slope (Cedeño-Fonseca 2019). This genus, composed of nomadic vines (Sperotto et al. 2020), belongs to Araceae subfamily Monsteroideae, and is the only Neotropical genus of the pantropical tribe Monstereae, or Rhaphidophora clade (Tam et al., 2004;Zuluaga et al. 2019). Despite a relatively recent revision (Madison, 1977), Monstera is taxonomically the most poorly understood genus of Araceae in the Neotropics (Grayum 2003). The morphological features manifest on herbarium specimens are often inadequate for characterization and identification, due to the large size of the plants and their extreme intraspecific variation (Grayum 2003). Madison (1977) believed that Panama had the highest diversity of Monstera species, but recent studies (e.g., Cedeño-Fonseca et al. 2018, 2020a, 2020b, 2020c, 2020d have elevated Costa Rica, with 32 accepted species of Monstera, to first place in this category. However, field work in Panama during 2016-2019, as part of an ongoing revision of Monstera for the Mesoamerican region (Croat et al., in prep.), has revealed the four new species here described, raising the Panamanian total for the genus to 29 species. All of these new species belong to Monstera section Monstera (sensu Madison, 1977: 90), characterized by seedlings with foliose leaves -unlike the stoloniferous sections Echinospadix Madison (1977) and Marcgraviopsis Madison (1977), and the juvenile stage with the leaves not appressed ('shingling') to the phorophyte (host tree).

MATERIALS AND METHODS
The first and second author carried out field exploration in Panama between 2016 and 2021 and studied Monstera collections deposited at the following herbaria: CR, HLDG, JVR, LSCR, MEXU, MO, NY, PMA, SEL, UCH, and USJ. Herbarium acronyms cited above and elsewhere in this paper follow Thiers (2021). Three of the four species described here are illustrated with photographic plates showing different parts of the plants in life, adapted from the "Lankester Composite Dissection Plate" technique proposed for Orchidaceae at Lankester Botanical Garden, Universidad de Costa Rica (Pupulin and Bogarín 2004). Due to the high demand for species of the genus Monstera as ornamental plants, and a rapidly growing black market that endangers native populations (even in protected areas), coordinates are here omitted from all specimen citations. Croat

Diagnosis
Monstera bocatorensis is characterized by its smooth and glaucous stems, long, smooth petioles glaucous throughout and 46-90 cm long, short petiole sheaths that extend only to the middle or ¾ of its length, usually deeply pinnatifid (rarely entire) leafblades, never perforate, and smooth, light green or dark green peduncles, 27-45 cm long, entirely covered by the cataphylls.

Etymology
The species is named after Bocas del Toro Province, Panama, where all the known specimens have been collected.

Distribution and habitat
Monstera bocatorensis is endemic to Panama, where it is known only from the western slopes of the mountains east of Fortuna Dam below the Continental Divide in Bocas del Toro Province, from sea level to 1100 m, in the Tropical wet forest and Premontane wet forest life zones.

Phenology
Fruiting has been recorded in March and June.

Conservation status
Monstera bocatorensis should be considered as data deficient (DD), because we lack adequate geographic distribution and population information to make an assessment based on the IUCN criteria (IUCN Standards and Petitions Subcommittee 2017; IUCN 2019).

Notes
This species is characterized by its ovate, yellowishdrying leaf-blades that are never perforate, frequently pinnatifid with two or three very unequal pinnae, or rarely entire. Other characteristic features are the short petiole sheaths that extend only to the middle or ¾ of its length, as well as the glaucous petioles and blades. This species is similar to M. glaucescens Croat & Grayum (Grayum 1997), but differs from that species by its leaf-blades drying light yellow-brown on the lower surface and with having the pinnae markedly unequal. In contrast, the leaves of M. glaucescens have blades that dry dark brown and have much narrower pinnae, with more long-tapered and more prominently falcate pointed lobes. Another species with which it could be confused is Monstera croatii M. Cedeño & A.Hay (in Cedeño et al., 2020c), but that species differs by its deeply pinnatifid and bluish green leaf blades, with bifid lobes, a persistent sheathing mucronate cataphyll, and spathe with two longitudinal keels.

Diagnosis
Monstera donosoensis is characterized by its dark green petioles with a deciduous or slightly persistent sheath, entire, pinnatilobed, or scarcely pinnatifid leaf blades, with or without fenestrations, spathe yellowish or cream externally and white or creamy internally, and flowers with the style hexagonal, strongly conical, and distally cylindrical.

Etymology
The species is named after Donoso District, Colón Province, Panama, in which the type was collected.

Phenology
Flowering has been recorded in January, March, April, June, August, October, November, and December. Fruiting has been recorded in January, February, March, April, July, and October.

Conservation status
The distribution of this species includes at least 10 locations of which seven are in protected areas. It has an EOO of 29, 214.84 km 2 and an AOO of 104 km 2 , therefore, M. donosoensis could be assessed as Least Concern [LC].

Notes
This species is characterized by its thick stems, with moderately short internodes, long, nearly fully sheathed petioles, with the sheath deciduous or slightly persistent, and moderately coriaceous, dark brown-drying, usually sparsely perforate, ovate-elliptic, and weakly acuminate leaf-blades, inequilaterally subrounded to acute at the base, with the primary lateral veins heavily aggregated near the base and the fenestrations (when present) large and few, mostly beginning near the midrib, as well as by its long-pedunculate inflorescences with the spathe greenish, cream-colored within, and the spadix about 2/3 as long as the spathe, and especially by its flowers with a protruding, hexagonal, strongly conical and distally cylindrical style. Monstera donosoensis is similar to M. dissecta (Schott) Croat & Grayum (1987), but differs in having petioles speckled with white dots, with the sheath deciduous or slightly persistent, coriaceous leaf-blades, and flowers with a hexagonal, strongly conical, and distally cylindrical style. Monstera donosoensis has similar characteristics to the South American M. adansonii Schott subsp. klotzschiana (Schott) Mayo & I.M.Andrade (2013), but the latter differs in having dark green, less frequently mottled petioles with the sheath persistent, and slightly coriaceous leaf-blades.

Diagnosis
Monstera gigas is characterized by petioles with white dots, a slightly persistent sheath, sometimes enormous leaf blades subcordate at the base, with entire margins, with or without fenestrations, and 24-65 primary lateral veins per side, sunken adaxially, departing the midrib at 80-90° in the lower part of the blade and 55-75° toward the apex.

Etymology
The epithet is a noun in apposition, from the ancient Greek word "gígas" meaning a giant, in reference to the exceedingly large size of its leaves, the largest recorded in the genus.

Distribution and habitat
Monstera gigas is endemic to Panama, where it is known only from the type locality in the region of the Fortuna Lake at 1200-1300 m, in the Premontane rain forest life zone.

Phenology
Fruiting has been recorded in January, April, July, and September.

Conservation status
Monstera gigas should be considered as data deficient (DD).

Notes
This species is characterized by its usually nomadic-vine (but sometimes terrestrial) habit (but sometimes terrestrial), large stems with short, stout internodes, subterete, pale yellowish brown petioles sheathed to within 13-17 cm from the base (to 36 cm on preadult leaves), and ovate-elliptic, grayish-drying, entire and non-perforated, short-acuminate leaf-blades, rounded at the base and with 24-65 primary lateral veins per side, as well as by its moderately short-pedunculate, massive, green-white spathes, green spadices, and flowers with a narrow style covered for nearly its entire width by the stigma, the latter bearing a tubular extension that protrudes beyond the end of its center. Leaves at the upper end of the size range for this species, exceeding 3 m in length, are the largest so far know in the genus, and the plant is perhaps the most massively constructed member of its entire subfamily. Monstera gigas was first collected by last author as sterile material in April 1980, and was assumed at the time to be a new species. Later the same year it was found fertile by Thomas Antonio. Because  of its large, entire leaves, it later became confused with M. standleyana G.S.Bunting (Bunting 1967), to which it is most probably closely related; however, the latter species differs in having fully sheathed petioles and dark brown-drying leaf-blades, rounded or acute at the base, with the basal veins arising at more acute angles and with short, pale lineations (as least on the upper surface), as well as by its flowers with a broader style and an oval stigma lacking a tubular extension.
One collection, Churchill 5508 (the holotype), was described as being terrestrial, making it exceptional for Monstera gigas; however, it may have ended up accidentally in that situation. The inflorescence of the same collection was reported to have harbored Dynastinae scarab beetles.

Diagnosis
Monstera titanum is characterized by its dark green stems with white dots, petioles 50-95 cm long, with the sheath slightly persistent, leaf blades subcordate at the base, with 20-40 primary lateral veins per side, departing the midrib at 75-95°, prominent collective veins, and compound fenestrations, with small fenestrations along the midrib or near the margins, and its inflorescence up to 95 cm in length.

Etymology
The species epithet, conveying enormous size, is from the greek 'titanikos' itself drawn from the Titans, the race of giant ancient Greek gods. It alludes to the huge size of the inflorescence, the largest known in the genus.

Distribution and habitat
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, at 1450-1480 m elevation in the Premontane rain forest life zone.

Phenology
Flowering has been recorded in January, March and July, and fruiting in March and November.

Conservation status
Monstera titanum should be considered as data deficient (DD).

Notes
This species is characterized by its juvenile plants with narrowly ovate, often perforated leaves and adult plants growing as nomadic vines with an appressedclimbing 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 Croat & M.Cedeño ( 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.