Cullenia exarillata

Cullenia exarillata (Tamil Name: வெடிப்பலா,^[2] Kadar (Anamalai hills) Name: முள்ளாலி,^[3] Muthuvan (Anamalai hills) Name: காரானி) is a flowering plant evergreen tree species in the family Malvaceae endemic to the rainforests of the southern Western Ghats in India. It is one of the characteristic trees of the mid-elevation tropical wet evergreen rainforests and an important food plant for the endemic primate, the lion-tailed macaque.^[4]

Cullenia exarillata
Cullenia exarillata tree
Cullenia exarillata fruiting branch
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Malvales
Family:	Malvaceae
Genus:	Cullenia
Species:	C. exarillata
Binomial name
Cullenia exarillata Robyns
Synonyms
C. excelsa, Durio ceylanicus, Durio exarillatus Wight[1]

Description

Tall evergreen trees with smooth greyish white bark, flaking in mature trees, with straight boles, frequently buttressed. The branches are horizontal often with series of knob-like tubercles (for cauliflorous attachment of flowers and fruits). The young branchlets and the underside of leaves are covered by golden brown peltate (or shield like) scales. Leaves are simple, alternate, glabrous, shiny green above and covered beneath with silvery or orangish peltate scales.^[5]

The tubular, hermaphroditic flowers (also covered by golden brown scales) are about 4–5 cm long and cream or pinkish brown in colour. The flowers lack petals and are formed of tubular bracteoles and tube-like calyx, obscurely 5-lobed. The round fruits, about 10–13 cm in diameter and covered with spines, are clustered along the branches. The fruit is a capsule, 5-valved, containing many reddish brown seeds about 4–5 cm long and 2–3 cm wide. In the fruit, the seeds are covered by a fleshy, whitish aril. The fruit dehisces open when mature and dry to release seeds.^[6]

Taxonomy

Cullenia exarillata, described by Robert Wight as Cullenia excelsa, and illustrated here by Govindoo

The genus Cullenia was created by Robert Wight and commemorates William Cullen with the type species excelsa from India which Wight considered incorrectly as being identical to the Sri Lankan C. ceylanica which was earlier described under the genus Durio. André Robyns examined Wight's specimen and fresh specimens from southern India and noted it as being distinct and described it as C. exarillata in 1970. C. ceylanica has the seeds covered by an aril whereas C. exarillata does not have the aril surrounding the seeds.^[7] The genus is evolutionarily close to Boschia and Durio.^[8]

Distribution and habitat

The species is characteristically found and dominant in the mid-elevation (700 m to 1400 m) tropical wet evergreen rainforests, which has been called the Cullenia exarillata - Mesua ferrea - Palaquium ellipticum type.^[9] It occurs from the southern tip of the Western Ghats in Kalakad-Mundanthurai Tiger Reserve and Agasthyamalai hills to Wayanad and Kodagu in the Nilgiri Biosphere Reserve.^[2][5][10]

Breeding system and dispersal

The hermaphroditic (or bisexual) flowers are mainly pollinated by bats (Cynopterus and Rousettus) and arboreal mammals (Lion-tailed Macaque, Brown Palm Civet, Indian Giant Squirrel, Nilgiri Langur, and Indian Giant Flying Squirrel).^[11] These mammals and other rodents that visit the flowers such as Dusky-striped Squirrel and Malabar Spiny Dormouse also act as flower predators as they consume a substantial number of flowers.^[12] The flowers are also visited by a number of bird species, including Indian White-Eye, Square-tailed Bulbul, Yellow-browed Bulbul, Brown-cheeked Fulvetta, Common Rosefinch, Kerala Laughingthrush, and White-cheeked Barbet.^[13] However, flowers visited by birds tend to be aborted.^[14]

Cullenia exarillata is an outcrossing species, producing negligible fruit-set under geitonogamy and no fruit-set under autogamy.^[14] The seeds are mechanically dispersed (gravity)^[15] as well as by Lion-tailed Macaques over short distances.

Ecology

Cullenia exarillata is a dominant tree species in the mid-elevation tropical rainforests (between 700 and 1,400 m elevation) of the southern Western Ghats.^[9] It is also among the most abundant canopy trees in relatively undisturbed mature wet evergreen forests.^[16] It occurs at a density of 20 trees/ha to 59.6 trees/ha in mid-elevation wet evergreen forests of the Anamalai Hills.^[16][17]

Individual trees were estimated to produce between 1300 and 26000 flowers (average = 8734) chiefly between February and May, followed by a fruiting peak between May and September, in a rainforest at the southern tip of the Western Ghats.^[13] In the Anamalai Hills further north in the southern Western Ghats, the species was observed flowering between October and February.^[17] As the tree flowers abundantly during the dry season, a period of fruit scarcity in the forest, the flowers attract many diurnal and nocturnal frugivorous mammals and birds, making the tree a possible keystone species in these forests.^[13] The flowers are low in nectar but contain fleshy sepals embedded with nectaries which are the main reward for animal visitors.^[14] The flowers are eaten by endemic arboreal mammals such as Lion-tailed Macaque,^[4][17] Brown Palm Civet,^[18] Indian giant squirrel, Bonnet macaque, and Nilgiri langur.^[17] The base of the sepals are consumed and the anthers and stigma are discarded.^[17]

Lion-tailed macaque consume the seeds and aril of Cullenia exarillata fruit

The seeds and flowers of this species form a major part of the diet of Lion-tailed macaque in mid-elevation rainforests: 24.8% of the annual diet in Puthuthottam forest fragment in the Anamalai Hills,^[19] 20.7% of annual diet in Silent Valley National Park.^[20] The seeds constituted about 20% of the annual fruit diet of the Lion-tailed macaque and 7.1% of Indian giant squirrel diet in mid-elevation rainforest of Pachapal Malai or Waterfall Shola in the Anamalai Hills.^[17] Seeds were also found to be a minor food resource (<1% annual diet) for Nilgiri langur in this study. In lower-elevation rainforests at Varagaliar in the Anamalai Hills, Cullenia exarillata comprised a smaller percentage (0.4 – 1.2%) of the annual diet of lion-tailed macaques, with the flowers, seeds, and aril being consumed.^[4] A seed predation rate of 45% has been estimated in a wet evergreen forest of the southern Western Ghats, caused by species such as Indian Giant squirrels that feed on unripe fruits (with softer spines) and Lion-tailed macaques that feed on ripe fruits (with hard spines).^[21] Seeds fallen on the forest floor also suffer high predation by mammals and insects, with 91.6% of the seeds predated in experimental plots open to all predators and 44% predated in plots where mammals were excluded.^[22] The study also reported that seeds of Cullenia exarillata were predated by three species of rodents (Malabar spiny dormouse, Rattus sp. and Indian crested porcupine), besides Indian spotted chevrotain, sambar, Indian muntjac, and a primate, Nilgiri langur.^[22] Seed predation is higher in rainforest fragments than in contiguous rainforests, which has been experimentally revealed to be largely due to predation by mammals.^[23]

Conservation

The species is endemic to the Western Ghats and has not yet been assessed for the IUCN Red List. The tree may persist in rainforest fragments showing similar levels of flowering and fruit-set, and may even have higher fruit-set in some disturbed sites and on isolated trees.^[24] Highly disturbed sites, including plantations where understorey vegetation and canopy trees were removed, have lower density of Cullenia exarillata.^[16]

Gallery

• 
  A Cullenia exarillata tree towering above others in the Anamalai Hills
• 
  Fruiting branch in canopy
• 
  Ripe fruits
• 
  Mature fruits
• 
  Mature fruits splitting
• 
  Mature fruits dehiscing open
• 
  Dehisced fruits of Cullenia exarillata still on the tree
• 
  Seeds of Cullenia exarillata
• 
  Young leaf before opening out
• 
  Upperside of leaves
• 
  Underside of leaves
• 
  Single flower
• 
  Nilgiri Langur feeding on a Cullenia exarillata seed
• 
  Indian spotted chevrotain feeding on a Cullenia exarillata seed
• 
  Nilgiri Langur picking a Cullenia exarillata seed
• 
  Indian muntjac approaching to feed on a Cullenia exarillata seed
• 
  Cullenia exarillata fruit in different stages

References

1. Wight, Robert (1852). Icones plantarum Indiae Orientalis :or figures of Indian plants. Volume 5. p. 23.
2. "Cullenia exarillata - BOMBACACEAE". www.biotik.org. Retrieved 2016-11-16.
3. மாதுரி ரமேஷ்; மனிஷ் சாண்டி; மேத்யு ஃபரேம் (2017). நாங்கள் நடந்து அறிந்த காடு [Walking is a way of knowing In a Kadar Forest] (in Tamil). India: Tara Books Pvt. Ltd., India. ISBN 978-93-83145-92-8.
4. Kumar, A. (1987) The ecology and population dynamics of the lion-tailed macaque (Macaca silenus) in South India. PhD thesis, Cambridge University, UK.
5. Brandis, Dietrich (1906). Indian trees: an account of trees, shrubs, woody climbers, bamboos and palms indigenous or commonly cultivated in the British Indian empire. London.: Archibald Constable and Co. Ltd. (1990 reprint Bishen Singh Mahendra Pal Singh). pp. 78. doi:10.5962/bhl.title.50463. hdl:2027/njp.32101048471120. ISBN 978-81-211-0051-9.
6. "Cullenia exarillata A. Robyns". India Biodiversity Portal. Retrieved 2016-11-16.
7. Robyns, André (1970). "Revision of the genus Cullenia Wight (Bombacaceae - Durioneae)". Bulletin du Jardin Botanique National de Belgique. 40 (3): 241–254. doi:10.2307/3667646. JSTOR 3667646.
8. Nyffeler, R.; Baum, D.A. (2000). "Phylogenetic relationships of the durians (Bombacaceae-Durioneae or /Malvaceae/Helicteroideae/Durioneae) based on chloroplast and nuclear ribosomal DNA sequences". Plant Systematics and Evolution. 224 (1–2): 55–82. doi:10.1007/bf00985266. S2CID 43469554.
9. Pascal, J. P. (1988). Wet evergreen forests of the Western Ghats of India: ecology, structure, floristic composition and succession. Pondicherry, India.: Institut Français de Pondichéry.
10. Gamble, J. S., and C. E. C. Fischer (1915–1935). Flora of the Presidency of Madras, Parts I to XI. (3 volumes). Adlard and Son Limited, London.
11. Devy, M. Soubadra; Davidar, Priya (2003). "Pollination systems of trees in Kakachi, a mid-elevation wet evergreen forest in Western Ghats, India". American Journal of Botany. 90 (4): 650–657. doi:10.3732/ajb.90.4.650. ISSN 0002-9122. PMID 21659160.
12. Ganesh, T.; Devy, M. Soubadra (2006). "Interactions between non-flying mammals and flowers of Cullenia exarillata Robyns (Bombacaceae), a canopy tree from the wet forests of Western Ghats, India" (PDF). Current Science. 90: 1674–1679.
13. Ganesh, T.; Davidar, Priya (1997). "Flowering Phenology and Flower Predation of Cullenia exarillata (Bombacaceae) by Arboreal Vertebrates in Western Ghats, India". Journal of Tropical Ecology. 13 (3): 459–468. doi:10.1017/s0266467400010622. JSTOR 2560295. S2CID 83574443.
14. Ganesh, T.; Devy, M. Soubadra (2000). "Flower Use by Arboreal Mammals and Pollination of a Rain Forest Tree in South Western Ghats, India". Selbyana. 21 (1/2): 60–65. JSTOR 41760054.
15. Ganesh, T.; Davidar, Priya (2001). "Dispersal modes of tree species in the wet forests of southern Western Ghats" (PDF). Current Science. 80: 394–399.
16. Muthuramkumar, S.; Ayyappan, N.; Parthasarathy, N.; Mudappa, Divya; Raman, T. R. Shankar; Selwyn, M. Arthur; Pragasan, L. Arul (2006). "Plant Community Structure in Tropical Rain Forest Fragments of the Western Ghats, India1". Biotropica. 38 (2): 143–160. doi:10.1111/j.1744-7429.2006.00118.x. ISSN 1744-7429. S2CID 54011462.
17. Sushma, H.S.; Singh, Mewa (2006-05-01). "Resource partitioning and interspecific interactions among sympatric rain forest arboreal mammals of the Western Ghats, India". Behavioral Ecology. 17 (3): 479–490. doi:10.1093/beheco/arj058. ISSN 1465-7279.
18. Mudappa, D.; Kumar, A.; Chellam, R. (2010). "Diet and fruit choice of the brown palm civet Paradoxurus jerdoni, a viverrid endemic to the Western Ghats rainforest, India" (PDF). Tropical Conservation Science. 3 (3): 282–300. doi:10.1177/194008291000300304. S2CID 56356587.
19. Menon, S. A. 1993. Ecology and conservation of the endangered lion-tailed macaque (Macaca silenus) in the landscape mosaic of the Western Ghats. PhD Thesis, Ohio State University, Columbus, Ohio, USA. 123 pp.
20. Kumar, A. (2013). Lion-tailed macaque. Pages 117-133 in A. J. T. Johnsingh and Nima Manjrekar (editors) Mammals of South Asia, Volume 1, Universities Press, Hyderabad.
21. Ganesh, T. (1995). Fruiting patterns among canopy trees and fruit use by vertebrates in a wet evergreen forest of the southern Western Ghats India. PhD Thesis, Pondicherry University, Pondicherry. 149 pages.
22. Krishnan, A. 2020. How does fragmentation alter seed predation patterns of rainforest tree species? MSc Dissertation, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India. 59 pp.
23. Krishnan, Aparna; Osuri, Anand M.; Krishnadas, Meghna (2022). "Small mammals reduce distance dependence and increase seed predation risk in tropical rainforest fragments". Biotropica. 54 (6): 1428–1439. doi:10.1111/btp.13137. ISSN 0006-3606. S2CID 250154441.
24. Devy, M. Soubadra (2006). Effects of fragmentation on a keystone tree species in the rainforest of Kalakad Mundanthurai Tiger Reserve, India Archived 2016-11-17 at the Wayback Machine. Unpublished Report submitted to Rufford Foundation, Ashoka Trust for Research in Ecology and the Environment, Bangalore, India.