Forest Ecology and Management
Forest disturbance and pollination of a keystone species in the rainforest of
Kalakad-Mundanthurai Tiger Reserve, India.
Investigators: Soubadra Devy and T.Ganesh
Duration: 2 years
Plant-animal interactions in tropical forests maintain local diversity of trees.
The loss of these pollinators due to human disturbance could affect the pollination
success of these trees and consequently their regeneration and survival. If these
trees are keystone species then it could affect the entire community. This project
will determine the effect of a depauperate mammal pollinator assemblage on the
reproductive efficacy of an important keystone tree species, Cullenia exarillata,
a dominant member of the evergreen forests of the southern Western Ghats. Visitation
rates and mammal activity on the trees and fruit set will be recorded at a disturbed
and undisturbed site to evaluate the relative pollination success of the trees.
The result of this study could help in restoring lost mammals in degraded ecosystems.
Results obtained so far indicate that 6 arboreal mammal species, 1 bat species, 16 bird
species, 2 species of butterflies, one social bee, and several species of smaller insects
visited the flowers of Cullenia exarillata. Wild boar (Sus scrofa) ate flowers fallen in
the ground below the trees. Cullenia exarillata is out-crossed and requires pollinators
for fruit production. The frequency of visitors to the flowers is more from diurnal flower
visitors than by nocturnal visitors. However, nocturnal visitors were responsible for
greater fruit set than diurnal visitors. This was consistent across years. The trees
received very few visits from the lion- tailed macaque in disturbed sites compared to
in the undisturbed sites. Giant squirrels visited the flowers more often in disturbed
sites. Lion-tailed macaques were lower in relative abundance in disturbed sites. Nilgiri
langurs and giant squirrels were disproportionately higher in the disturbed sites.
Mammal abundance in different sites was dependent on Cullenia flowering. Occurrence
of lion-tailed macaque is dependent on the flowering of Cullenia exarillata in the forest.
Fruit bats play an important role in promoting pollination of Cullenia in disturbed
sites. Fruit set in disturbed sites was less compared to undisturbed sites.