Lagenandra rubra Madola, Jayasinghe, Yakand. & K.Yakand., 2025

Madola, Indrakheela, Jayasinghe, Himesh, Yakandawala, Deepthi & Yakandawala, Kapila, 2025, Lagenandra rubra (Araceae), a new endemic species from Sinharaja Man and Biosphere Reserve, Sri Lanka, Phytotaxa 689 (2), pp. 233-242 : 235-239

Lagenandra rubra Madola, Jayasinghe, Yakand. & K.Yakand. , sp. nov. ( Figs. 2–5 )

The spathe of L. rubra slightly resembles that of L. toxicaria var. barnesii Fischer (1938:126) but could be separated by the spathe color been glossy dark red-maroon oppose to light greenish pink/pinkish cream or very pale brown spathe; long limb (ca. 8.0– 11.5 cm) oppose to shorter limb (ca.3.0 cm); longer spadix (ca. 2.4–2.6 cm) oppose to shorter (ca. 1.8 cm); lower number of pistillate (ca. 40–45) and staminate flowers (ca. 94–100) oppose to larger number (ca. 70–80 and ca. 175–200 respectively). The leaves resemble those of L. limbusleviterapertae , but can be differentiated by the presence of undulate margins.

Type:— SRI LANKA, Sabaragamuwa Province, Rathnapura District, Sinharaja Man and Biosphere Reserve, 577 m asl. 08 March 2022, Madola, Jayasinghe, Yakandawala & Yakandawala L 259 [holotype PDA! ( PDA 00109887), isotypes PDA! ( PDA 00109888, PDA 00109889), K!].

Evergreen large herb with creeping to erect rhizome ca. 1.8–2.3 cm in diam. Cataphylls ca. 11.0–15.0 cm, dark maroon. Petiole ca. 18.0–36.0 cm long, ca. 0.3–0.6 cm wide, sheath ca. 2.0– 4.5 cm long, unequal. Leaf blades upper surface green, lower surface light green, blades more or less oblong, apex narrowly acute, base gradually tapering/acute, margin undulate, blade ca. 22.5–32.0 × 5.0– 7.5 cm; midrib visible on upper surface. Peduncle ca. 2.5–8.0 cm long, 0.5–0.7 cm width. Spathe glossy dark red-maroon, warts absent, ca. 18.5–20.7 cm long, kettle ca. 2.0–5.5 × 0.5–1.6 cm, glossy dark maroon longitudinal striations inside; limb ca. 8.0–11.5 × 3.5–5.5 cm, twisted; tail ca. 5.5–8.5 × 0.1–0.3 cm. Spadix ca. 2.4–2.6 cm long; pistillate flower zone ca. 0.4–0.5 × 0.5–0.7 cm; sterile zone ca. 1.0– 1.2 cm long; staminate flower zone ca. 0.6 × 0.4 cm; appendix ca. 0.3–0.4 × 0.3–0.4 cm. Pistils ca. 40–45. Staminate flowers ca. 94–100.

Distribution and phenology:— To date distribution of L. rubra appears to be restricted to a single locality in Sri Lanka, in the Sinharaja MAB. During the initial observations we recorded nearly 100 individuals, however during the subsequent visits we have noticed a reduction in the number of individuals and at present only around 60 individuals survive. This population is situated at the top of a small waterfall created by the streamlet. The population consisting of both mature and young individuals which are distributed along the bank and in small rock pockets of this streamlet spread over about 5 m distance.

Sinharaja (MAB) is one of the largest tropical rainforest (11331 ha) in southwestern lowlands of Sri Lanka, rich in floral and faunal diversity. It is located in the Sabaragamuwa and Southern provinces, spanning the Ratnapura, Galle, and Matara administrative districts. Sinharaja Forest Reserve was nominated as UNESCO’s World Heritage site in 1988. The Western Ghats and Southwestern Sri Lanka are considered one of the 34 biodiversity hotspots, including the Sinharaja MAB ( Myers et al. 2000, Mittermeier et al. 2004, 2011). This highlights both the region’s high endemism and the environmental threats it faces, especially due to anthropogenic activities. The majority of the endemics are in the south western region including the low country wet zone and the central highlands of the country ( Gunatilleke & Gunatilleke 1991, Senanayake 1980). In addition to L. rubra , the forest reserve harbors several other important threatened amphibious and aquatic plant species, such as L. bogneri de Wit (1978: 33–34) , L. thwaitesii Engler (1879: 621) , Aponogeton rigidifolius Bruggen (1962: 91) , and Cryptocoryne Fisch. ex Wydler (1830: 428) . However, it is important to note that between 1972 to 1977, Sinharaja forest reserve was significantly destructed by logging activities to supply timber to the plywood industry ( Sri Bharathie 1979, NCR 1997).

Peak flowering of L. rubra was observed from February to April. However, despite several visits to the site during the period from 2022 to 2024, we were unable to observe fruiting following the flowering season. The only instance of observing immature fruit was in May 2023. Due to heavy rains during the monsoon season, which created rapid water currents, we were unable to observe any mature fruit during subsequent field visits.

Habitat:— The plants inhabit a shady streamlet in a Primary Tropical Rainforest.

Eponymy:— The specific epithet rubra highlights the distinctive red-maroon color of the spathe.

Vernacular name:—රත් ෙකතල ‘(Rath Kethala)’.

Other specimens examined (paratypes):— Lankagama-Ilumba kanda trail, 2022 Feb 23, H.Jayasinghe, D.Dhanushka, S.Kanishka HDJ 1493 ( PDA! PDA 00109825).

Proposed conservation status:— So far L. rubra has been found only from its type locality. Estimates for its EOO and AOO are 4 km 2 due to its occurrence in only one locality. Considering Criteria B, both under sub criterion B 1 and B 2, EOO (<100 km 2) and AOO (<10 km 2) L. rubra meets the CR thresholds. However, in order to qualify for this threatened category, species must meet at least 2 conditions of the three specified (a), (b) and (c). The habitat of L. rubra is an evergreen tropical forest but is continuing decline or degraded due to fast water currents occurred perhaps due to intensified rain fall catalyzed by climate change. Further Rhizomes were eaten by wild boars as well. Now the population has reduced compared to the first sighting. Hence an immediate ex-situ conservation program is needed. The genus is pollinated by insects and the decline in seed set could be attributed for the absence of the particular insects (Order Diptera ) in the environment. In addition to habitat loss, decline in area of occupancy, no of locations and the population size qualifies for both sub-criteria (a) and (b). Further there is no information available to determine if any extreme fluctuations are happening for this species. Further L. rubra could be evaluated under Criterion D, very small or restricted population which increase the risk of extinction. With a population size of around 60 L. rubra qualify for Endangered category ( EN D). During the evaluation of the IUCN Red List conservation status of a taxon under more than one category resulting different statuses, it is recommended to select the highest threatened category for which the taxon qualifies. Therefore, L. rubra qualifies to the CR category under criterion B, CR B 1ab (ii, iii, iv, v) +2ab (ii, iii, iv, v).

Figures

FIGURE 2. Habitat of L. rubra.

FIGURE 3. Habit of Lagenandra rubra.

FIGURE 4. Lagenandra rubra; A. Leaf. B. and C. Spathe from different angles showing the opening in the limb. D. Kettle with the spadix. E. Pistillate flower zone. F. Appendix and staminate flower zone.

FIGURE 5. Lagenandra rubra; A. Habit. B. Spathe.