Lagenandra srilankensis Madola, D.Yakandawala & K.Yakandawala, 2021

Madola, Indrakheela, Yakandawala, Deepthi, Yakandawala, Kapila & Karunaratne, Senani, 2021, Two new species of Lagenandra (Araceae) from the Wet Zone of Sri Lanka, Phytotaxa 522 (3), pp. 187-199 : 193-197

Lagenandra srilankensis Madola, D.Yakandawala & K.Yakandawala , sp. nov. ( Figs. 5–7 )

The habit of L. srilankensis resembles L. bogneri and L. jacobsenii in vegetative state but can be easily separated by the presence of the faint silver line in leaf margin. The occurrence of a faint silver margin relates the species with L. thwaitesii , the only other species in the genus with this feature. However, the silver margin in L. srilankensis appears faint against the light green colour of the leaf blade oppose to the dark green leaves of L. thwaitesii . The silver margin appears conspicuous while the leaf is wet. The size and the shape of the leaves of the two species also differ; the leaves are large and ovate in L. srilankensis , while in L. thwaitesii the blade sublinear, 10 × longer than broad. However, during the flowering they can be easily separated by their distinctive spathes; L. thwaitesii with a shorter peduncle and a more than half twisted spathe opposed to the longer peduncle and less than or untwisted spathe of L. srilankensis .

Type:— SRI LANKA, Western Province, Colombo District, Labugama Kalatuwawa Forest Reserve , 165 m asl, Collected 28 March 2018, Madola, Yakandawala & Yakandawala L33 (holotype PDA!, isotype PDA!)

Large evergreen herb with creeping to erect rhizome ca. 0.8–2.0 cm in diam. Cataphylls ca. 6–13 cm. Petiole ca. 17–32 cm long, ca. 0.3–0.7 cm wide, green-maroon and rugrose; with protuberances (multicellular hairs), sheath ca. 3–8 cm long, unequal. Leaf blades green with a faint silver margin that is very conspicuous while wet; ovate to narrowly ovate, apex acute, base round, unequal/oblique, margin entire, blade ca. 16–24 × 4.5–9.0 cm; midrib visible on both surfaces and prominent on the lower surface; lower leaf surface rugrose and with protuberances. Peduncle ca. 1.0– 10.5 cm long, 0.3–0.6 cm width, light maroon, terete. Spathe light maroon, slightly rugose with no distinct warts, ca. 6.5–8.8 cm long, kettle ca. 1.3–2.0 × 0.9–1.5 cm, dark maroon with smooth longitudinal striations inside; limb ca. 2.7–4.0 × 1.0– 2.5 cm, opening by a slight twist, dark maroon and horizontally ribbed inside; tail ca. 1.5–3.5 cm. Spadix ca. 1.0– 1.6 cm long; pistillate flower zone ca. 0.3–0.5 × 0.4–0.6 cm; sterile zone ca. 0.3–0.7 cm long (light pink); staminate flower zone ca. 0.2–0.4 × 0.2–0.3 cm; appendix ca. 0.1–0.2 × 0.1–0.2 cm long (dark maroon). Pistils ca. 28–32, cream brown with pink stigma, oriented upright. Staminate flowers ca. 65–70. Infructescence up to 9 cm long, prolate with 28–32 fruitlets, peduncle 2.5–6.5 cm long, fleshy capsules up to 10, with warty outgrowths. Seeds 2–4, size ca. 0.5–0.6 × 0.1–0.3 cm and longitudinally ridged.

Distribution, phenology and conservation status:— To date, the distribution of L. srilankensis has been recorded from three localities in the Western Province of Sri Lanka. The population within the Labugama Kalatuwawa Forest Reserve harboured only 10 mature individuals along a stream. The other population that occurred just outside the forest reserve, along a stream, contained only 6 mature individuals. It was noted that both populations did not contain any young individuals. The aerial distance between the two populations is approximately 1.3 km. The healthier population in Wewila occurred along the Korala-ema-dola.The Korala-ema-dola is a stream that serves as the demarcation between Colombo and Kalauthara districts, Western Province, of an elevation of 157 m asl. This population is spread along the border of privately owned lands on both banks. The plants are concentrated in to two places, with a distance of 50 m in between, each patch spreading about 2– 6 m. Since the populations are outside a protected area or forest reserve, they are exposed to anthropogenic activities. They inhabit the banks of the stream and are vulnerable to strong water current during the rainy season. One patch harboured 10 mature individuals with few young plants, while the other had 15 individuals.

Peak flowering in L. srilankensis was observed from January-April and occasional flowering in June-July. Fruiting from February-August. The open inflorescence persists for 3–4 days.

The calculated AOO accounted to 12 km 2 while the EOO was 1.8972 km 2. Since the EOO was less than AOO, the EOO was also taken as equal to AOO. According to the field data L. srilankensis is restricted to three localities in Sri Lanka. The number of healthy individuals in the protected area, Labugama Kalatuwawa Forest Reserve is limited to few individuals (10) and are scattered while the population outside also harboured a few (6) mature individuals. The healthier larger population (25) occurs in Wewila area in a stream that runs across a village. Due to this reason, the population is subjected to anthropogenetic activities, which is a direct threat to the population. The plants occupy the bank of the stream, and as the Wet Zone experience very heavy rains, there is a possibility that heavy water currents would remove individuals from the bank. Further, the observation made during the past three years, we have noticed the deposition of silt and debris over the young individuals after the rains. Therefore, the two populations could be considered as exposed to anthropogenic threats.

Following the present IUCN (2019) guidelines, based on Criteria B- the geographic range, with only 12 km 2 of EOO, the species qualifies for the Critically Endangered category (CR) under the thresholds for B1. However, as the AOO exceeds 10 km 2 the species cannot be considered as qualifies as CR but as Endangered (EN) under Criteria B2. According to our field experiences, L. srilankensis exhibits a linear distribution along streams. In addition, these plants are herbs where their maximum height does not exceed 40 cm and therefore calculating the AOO with a 2 km × 2 km grid provides an over-estimated AOO value. This scenario is highlighted by Manawaduge et al. (2020), where the smaller aquatic plants with high habitat specificity are at a disadvantage when securing their conservation statuses, when a 2 km × 2 km grid is employed and thereby lose the protection they deserve through legislations. If the AOO was calculated by using a 1 km × 1 km grid, L. srilankensis would secure only a AOO of 3 km 2 which would be a more reasonable estimation. Considering the conditions of Criteria B, the species fulfills, (a) severely fragmented; (b) Continuing decline observed, estimated, inferred or projected in (iii) quality of habitat and (v) number of mature individuals. Therefore, L. srilankensis could be considered as Critically Endangered under B1ab (iii, iv). In addition, taking Criteria C into account, with the number of mature individuals been less than 250 and with an estimated, projected or inferred continuing decline in the mature individuals where (a) (i) number of mature individuals in each subpopulation less than 50, and (ii) % of mature individuals in one subpopulation is 90–100%, L. srilankensis qualifies for CR under C2 (a) (i, ii). Therefore, L. srilankensis Qualifies for Critically Endangered category under B1ab (iii, iv) + C2 (a) (i, ii).

Habitat:— The plants occupy the banks of small water courses, streams and streamlets.

Eponymy:— The new species is named after Sri Lanka, an island that is rich in biodiversity, that also harbors 11 species of Lagenandra of the totally described 19 species of the world, with 10 endemics.

Other specimens examined (paratypes):— SRI LANKA. Colombo and Kaluthara District boarder, Wewila along the Korala-ema-dola, Udagama area of Sri Lanka, 157 m asl, Collected 12 February 2019, Madola, Yakandawala & Yakandawala L70 ( PDA!, K!) . Colombo District , outside Labugama Kalatuwawa Forest Reserve, 90 m asl, Collected 19 February 2021, Madola, Yakandawala & Yakandawala L239 ( PDA!) .

Figures

FIGURE 5. Lagenandra srilankensis; A Habitat, B and C Habit.

FIGURE 6. Lagenandra srilankensis; A. Leaf, note the silver margin. B. and C. Spathe from different angles showing the opening in the limb of the spathe giving access to the reproductive organs. D. Spathe dissected and opened. E. Kettle with the spadix; note the dark maroon wall with smooth longitudinal striations. F. Pistillate flower zone with cream brown pistils and pink stigma that are oriented upright. G. Appendix and staminate flower zone. H. Infructescence and I. Seeds.

FIGURE 7. Lagenandra srilankensis; A. Habit. B. Spathe. C. Infructescence and D. Seeds.