Mutualistic Relationships of Cycas circinalis L.

SOME FIELD NOTES FROM THE APPANKAAPPU FORESTS, NILAMBUR, KERALA, INDIA

Saneesh C S & Anita Varghese

INTRODUCTION

The Nilgiri Biosphere Reserve spreads over three states and extends over an area of 5520 sqkms. On the western side of the NBR are the forests of Nilambur, one of the biodiversity hotspots of the world, harboring several endangered and endemic flora and fauna; some of these species may not yet be documented. The Nilambur region, bordering the Silent Valley and the Mukurthi National Parks on the southern and eastern sides respectively, receives an annual rainfall of 3000 mm. The forests vary from the tropical evergreen to the semi deciduous and are characterized by Cullenia sp., Myristica sp., Pallaquim ellipticum, Messua ferrea in the evergreen belts and Terminalias, Lagerstroemias, Dillenia sp. and Bamboo in the moist and dry deciduous tracts.

Chaliyar is the chief river in this forest, its source at an altitude of 2000 m in the Elambileri Hills; the main tributaries are the Karimpuzha, Cherupuzha,
Talipuzha, Panapuzha, Korampuzha, Karipuzha, etc. Many important indigenous peoples live in these forests, their lifestyles adapted well to their
environment. Some of these groups are the Cholanaickan, Pathinaickan, Paniyan, Aranadan, and Malamuthan.

The local name for C.circinalis is eentha. It is fairly abundant in the area and represented in all stages. Cycad populations have been observed in semievergreen and moist deciduous forests at elevations ranging from 30-100 m Many plants were also found growing within the teak plantations and bamboo thickets of the area.

HUMAN USE OF C.CIRCINALIS

Forest peoples harvest eentha seeds in plenty for consumption. The seeds are smoke-dried and leached several times, then powdered into flour and made into pancakes. According to an elderly Paniya lady of Nedumkayam village, “we can make anything with eenthapodi (eentha flour)!” There is a significant demand for processed eentha seeds in the local market, and gatherers often sell a portion of their harvest.

The tender new leaves of the plant are also broken off, cut into bits, and left overnight in water before being cooked and eaten; mature leaves are
harvested to decorate temples during festivals. The male cones are also much sought-after by local paddy farmers. The cones are placed in the center
of the fields to repel pests that attack the ripening crop; this practice has also been reported among farmers in Karnataka. (R. Ganesan, personal
communication).

INSECTS AND C.CIRCINALIS

The plains Cupid Butterfly (Edales pandava, Family Lycaenidae) uses Cycas circinalis as its host plant. In early May 2007, an adult butterfly was observed
on young cycad leaves. Within days, the larvae emerged and were feeding on the young shoots. The cycad had also begun producing a new flush of leaves as if in response to the larval needs. When they were finished feeding, the larvae then huddled together at the base of the leaves, pupated, and within a period of 7-9 days emerged in a burst of blue.

Two species of ants were also observed on Cycas circinalis trees. One was collecting the secretions found on the hairs of the young unfurling leaves
of the cycad, while the other was observed collecting secretions from the bodies of Cupid Butterfly larvae. Mann (1999) reports that a gland on the back of the caterpillar secretes a liquid containing sugar and amino acids that helps sustain
the ants. The ants benefit from this secretion, and the caterpillars are not harmed in any way. The ants repay the caterpillars by protecting them from any
would-be predators.

De Vries and Poinar (1997) discuss an amber fossil they found of a caterpillar that possessed the major organs used by extant caterpillars in relationship with ants: tentacle nectary organs, balloon setae, and vibratory papillae. The fossil was dated at 15- 20 million years old. Could this be an example of an ancient symbiosis between butterflies, ants, and cycads?

Dammer bees (Trigona spp., Family Meliponidae) were also observed collecting secretions from tender new cycad leaves. Bees make ‘propolis’— a powerful, natural, antibacterial and antiviral food—by collecting resinous sap from trees and then mixing it with wax back at the hive. This food keeps them resistant to bacterial and viral infections that can otherwise wipe out their colonies (R. Leo, personal communication). The dammer bees are often seen taking resinous sap from various extra floral sources, and the secretions on the hairs of newly emerging cycad leaves are quite sticky and resin-like.

OTHER MAMMALS AND C.CIRCINALIS

Though no direct observations were made with regard to non-human mammals, indigenous people in the area have often brought seeds of Cycas circinalis that had been ‘eaten’ and discarded by fruit bats. On the banks of the Neerpuzha River, there have been observed many colonies of bats. The flying fox (Pteropus giganteus) is a fruit bat that feeds solely on the juice of fruits extracted by chewing dry the fleshy pulp which is then spat out (Prater, 1971). During the monsoon, coning cycad trees represent one of the few ‘fruits’ available and which are foraged on by flying foxes that play a role in seed dispersal. The Sambar (Cervus unicolor), one of India’s largest deer species, is also found in the forests in Nilambur. It too feeds on fallen cycad seeds. According to a local village person, excessive removal of cycad seeds by harvesters leaves little for the bats to feed on.

SUMMARY

The Cycas circinalis plants that were observed during the course of research in the forests of Nilambur have shed much light on the multi-faceted role of a single ‘keystone’ species within this unique and endangered ecosystem. Besides the ants, butterflies, and bats, epiphytes have been found growing on the bark, spiders often weave their webs across the leaflets, and bamboo seedlings have been observed germinating on the surface of a cut cycad stem.

The cycads have survived against all odds, even when their early companions, the dinosaurs, lost out. But what lies ahead for this species that has withstood the test of time for so many millennia? And what, then, will be the fate of the numerous organisms that depend on it?

Acknowledgements:

The full article was published in the newsletter of the The Cycad Society, USA. We are grateful to Jody Haynes for his comments and editorial suggestions. The authors are indebted to the indigenous people of the area who have accompanied us to the sites and shared their insights. We are also grateful to the Kerala Forest Department for their cooperation.

References:

1. DeVries, P.J. & G.O. Poinar. 1997. Ancient butterfly-ant symbiosis: Direct evidence from Dominican amber. Proceedings of the Royal Society of London, Series B- Biological Sciences 264(1385):1137-1140.

2. Mann, J. 1999. Myrmecophily: Ants and Butterflies – The Evolution, Effects, and Maintenance of their Relationships. Website: www.colostate.edu/Depts/Entomology/courses/en507/papers_1999/mann.htm. Accessed 09/04/07.

3. Prater, S.H. 1971. The Book of Indian Animals. Bombay Natural History Society.