ALOCASIA EPILITHICA
ORIGINAL DESCRIPTION:
Ab Alocasia scabriuscula N.E. Brown minore robusta, folii lamina minus crassa, utrinque viridis. Spatha pallide viridis, spadicis inflorescentia mascula et interstitio eburnei.
Serebryanyi, K.Z.Hein & Naive
SYNONYMS: N/A
DISTRIBUTION: MYANMAR | Originally collected by Moe Wint Wint Zaw from Tanintharyi Region, Myeik District, Tanintharyi Township, Lal Taung Yar Village, near Chay Taw Yar Taung Pagoda, ca 400 m a.s.l. Cultivated in Monywa by K. Z. Hein, 17 Apr 2022, K.Z. Hein 044 (holotype KKU).
Map showing the distribution of Alocasia epilithica with a star indicating its type locality, circle indicating the locality of the paratype and triangles indicating the documented populations of the new species
CLIMATE: Subtropical humid climate
Humidity is moderate throughout the year, ranging from 60% to 70%
Temperature is varies between the seasons - within the range of 48°F/9°C to 88°F/31°C during the day. Minimum temperatures never dip below 45°F/7°C
Rainy and humid season (October to May) and a dry season between June and October. The average annual rainfall is 1,200 mm
ECOLOGY: Alocasia epilithica is known so far from its Myanmar type locality and two localities in Peninsular Thailand: Suratthani and Nakhon Si Thammarat Provinces. Both localities in Thailand represent Karst-limestone formation/terrain at 30–200 m a.s.l., we strongly suspect the same for the one in Myanmar. Keeping in mind distribution ranges of the taxonomically-related Alocasia species closely connected with Karst-limestone formations, we consider that pattern to be important both from ecological and geographic standpoints. Confirmation of A. epilithica distribution in Peninsular Malaysia is strongly envisaged (see the taxonomic notes and affinity paragraph for the details). In Myanmar locality several individuals were observed growing as epilithic or terrestrial in tropical evergreen forest with a closed to semi-open canopy at around 200–500 m a.s.l. The discovery of A. epilithica is yet another example of the close phytogeographic relationship between northeast Malay Peninsula and Borneo (Corner 1960, Ahmad Sofiman and Boyce 2010). This species deserves further field studies and collecting to find other populations in neighboring areas and gather information on intra- and inter-population variation. With the distribution information currently limited and no information regarding to the different threats on its habitat, we herein propose this species to be treated as ‘Data Deficient’ (DD) following the Red List criteria of the IUCN Standards and Petitions Subcommittee (2019).
Habitat preferences of Alocasia epilithica sp. nov. in Tanintharyi Region, Myanmar (A) habitat, (B) plant in habitat growing on wall of limestone, (C) plant in habitat growing in forest floor, (D) juvenile plants with peltate posterior lobes in habitat. Photos by Moe Wint Wint Zaw.
SPECIES DESCRIPTION:
Moderately robust, epilithic or terrestrial mesophytic herb, up to 75 cm tall. Rhizome shortly erect, later decumbent, 2.5–3.0 cm in diameter. Leaves several together (up to 10); cataphylls slightly fleshy, pale green, later marcescent brown, lanceolate, ca 11.5 cm long; petioles 40–50 cm long, ca 1 cm in diameter, terete, glabrous, pale green, sheathing in the lower 1/3–1/2; petiolar sheaths broad, subcoriaceous, persistent, margins minutely hyaline; leaf blades thinly leathery, juvenile blades peltate with posterior lobes united for 30–50% of their length, in adult plants mostly all non-peltate, ovate-sagittate, 32–40 × 18–22 cm, widest at or slightly distal to junction of petiole, glabrous on both sides, adaxially green, abaxially pale green, margin sinuate; anterior lobe apex acuminate and mucronate; mucro ca 4 mm long; anterior costa prominently raised on both surfaces, with 4–5 primary lateral veins on each side, diverging at ca 80° proximally, the distal ones at ca 50°, running almost straight to the margin and joining a submarginal vein; secondary venation fine, forming a vague interprimary collective vein, slightly raised adaxially, slightly impressed abaxially; tertiary veins flush with the lamina both adaxially and abaxially; posterior lobes about 1/3 the length of the anterior, apex acute; posterior costae diverging at ca 50°, naked in the sinus for ca 1.5 cm.
(A) habit, (B) leaf blade Photos by K. Z. Hein.
INFLORESCENCE:
Inflorescences ca. 6 together, subtended by narrowly lanceolate membranous cataphylls; peduncle 16–18 cm long, 0.8–0.9 cm in diameter at anthesis, terete, glabrous, pale green, exceeding cataphyll; spathe 14–15 cm long; lower spathe 3.0–3.5 cm long, 2.0–2.2 cm in diameter, ovoid to slightly barrel-shaped, greenish yellow, base convolute; spathe limb 10.5–11.5 × 3.5–3.7 cm, oblong lanceolate, pale green at the tip, remainder greenish white, at first erect, then sharply deflected, apex acute and mucronate, longitudinal veins distinct; mucro ca 8 mm long; spadix 9.0–10.7 cm long, shorter than the spathe; stipe 2–3 mm long, conical, white. Pistillate flower zone 1.4–1.6 cm long, 1.3–1.4 cm in diameter; pistils slightly congested, facing obliquely outward; ovaries ovoid, ca 3 mm long, 2.0–2.5 mm in diameter, pale greenish-white to white; style ca 1 × 1 mm, white; stigma 2–3-lobed, the lobes drop-shaped, spreading, ca 1.5 mm in diameter, greenish-white, shining, sticky; sterile interstice 6–8 mm long, 7–8 mm in diameter, covered with three rows of rhombo-hexagonal synandrodes; synandrodes 2.5–3.5 mm in diameter, ivory white. Staminate/male flower zone 2.7–3.0 cm long, 7–8 mm in diameter, subcylindric, slightly constricted ca 1/2 from the base corresponding to spathe constriction; synandria rhombo-hexagonal 3–4 mm across, 4–6-merous, opening by apical pores; synconnective not expanded, ivory white; appendix roughly isodiametric with staminate flower zone, 4.0–5.2 cm long, gradually tapering to a blunt point, faintly longitudinally brain-like channeled, dull pale cream to yellowish. Peduncle of infructescence up to 30 cm long, ca 1 cm in diameter, remaining erect. Fruiting spathe ovoid, ca 3 cm in diameter, light green to greenish white at fruit maturation, splitting longitudinally into several unequal strips, these reflexing to reveal the ripe berries. Berries subglobose, ca 1 cm in diameter, glossy bright orange red.
Observed flowering in April and December – in cultivation. In Thailand, observed flowering and fruiting in the wild in June and September.
(C) inflorescence at early pistillate anthesis, (D) front view of inflorescence at pistillate anthesis, (E) spadix at pistillate anthesis with the nearside spathe artificially removed, (F) side view of inflorescence at pistillate anthesis, (G) detail of pistillate flower zone, interstice and lower part of staminate flower zone. Photos by K. Z. Hein.
VARIEGATED FORMS: N/A
ETYMOLOGY: The epithet ‘epilithica’ pertains to the ecology of the species.
Epi- (ἐπί): The prefix "ἐπί" means "upon" or "on top of" in Greek.
Lithos (λίθος): The word "λίθος" means "stone" or "rock."
Combined, they describe something that lives or grows "upon a stone" or "on rocks," emphasizing the plant's lithophytic nature.
NOTES:
Alocasia epilithica clearly belongs to Alocasia princeps Complex sensu A.Hay (1998). Habitually we considered the closest taxon to Alocasia epilithica to be enigmatic ‘Alocasia sp. nov. B’ listed and keyed in Araceae treatment in Flora of Thailand by Boyce and Sookchaloem (2012; p. 20, 30). Unfortunately, herbarium material of the taxon includes only sterile and fruiting specimens. Until very recently it has been at least problematic and irresponsible to discuss the alliance without studying flowering plants from that locality. Finally, the locality was revisited by Ms Patra Sangdanuch in June 2022 and flowering and fruiting plants were recorded (Fig. 4, 5). The locality area represents classical Karst-limestone formation/terrain (informative photos and video proved that). Thus, it became obvious that Alocasia epilithica and Alocasia sp. nov. B are conspecific. Herbarium specimens of Alocasia sp. nov. B herewith are included in authentic material of Alocasia epilithica as paratypes. Recent collection made by Ms. Patra Sangdanuch in June 2022 near Wat Chai Khao in Nakhon Si Thammarat Province and Wat Khao Niphan in Surat Thani Province proved another localities for Alocasia epilithica in Peninsular Thailand karst limestone forest at ca 100 m a.s.l. (Fig. 3).
Based on overall morphology, this new species could be compared with Alocasia scabriuscula N.E. Brown from Borneo and Alocasia farisii Zulhazman, Norzielawati & P. C. Boyce from Peninsular Malaysia and the closest allies of the latter (like Alocasia reversa N.E. Br.), being although very different from those species.
Alocasia epilithica is strikingly different from Alocasia scabriuscula in having completely green smooth petiole (versus scabrid or minutely pubescent petiole ornamented with irregular purple-brown dots, circles and stripes in Alocasia scabriuscula), green lamina (versus grey-green lamina in Alocasia scabriuscula) and plain pale green or greenish white spathe (versus white to ivory spathe covered by numerous purple-red blotches in Alocasia scabriuscula). Peduncle in Alocasia scabriuscula is also marked by purple stripes which are absent in Alocasia epilithica.
The new species is easily distinguished from Alocasia farisii in having different pistillate flower zone of spadix: Alocasia farisii has obligatory 2-lobed stigma and flask-shaped pistils, facing obliquely upwards versus 2–3-lobed stigma with drop-shaped spreading lobes, facing obliquely outwards/perpendicular to the spadix axis in Alocasia epilithica. Besides, the proportions of spathe and spadix are very different in those species. It deserves mentioning that Alocasia epilithica is almost certainly the species (yet to be seen flowering) present at the type locality of Alocasia farisii (Boyce 2022, pers. comm.).
There is no red/purple coloration in any parts of Alocasia epilithica , which is strikingly different from Alocasia reversa (having purplish inner surface of spathe limb) and Alocasia princeps W.Bull (limb of the white to yellowish-ivory spathe has purple margins or spathe is bright-purple throughout). Staminate flower zone of Alocasia epilithica is only half enclosed in the lower spathe chamber versus being entirely enclosed in Alocasia reversa.
Alocasia epilithica shows the same syndrome as Alocasia ridleyi A. Hay, having both, 2- and 3-lobed drop-shaped stigmas of female flowers. Hay (1998) considers Alocasia ridleyi to be intermediate between Alocasia princeps and Alocasia scabriuscula in that respect. Evidently, Alocasia princeps complex is currently far from taxonomic resolution and deserves special attention (as also proposed by Hay (1998)).
Other specimens examined (parartypes)
Peninsular THAILAND: Surat Thani Province, Khao Phra Rahu (Wat Sathit Khirirom), at 44 km road Surat-Takuapa, 50–200 m a.s.l., 22 Sept 1963, fruiting, T. Smitinand & H. Sleumer 1218 (L [barcode L.1409144-image!]); Surat Thani Province, Khao Lak, at 46 km of road Surat-Takuapa, 30–170 m a.s.l., 21 Sept 1963, fruiting, T. Smitinand & H. Sleumer 1200 (L [L.1409143-image!]).
CULTIVARS: N/A
HYBRIDS: N/A
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