Little is known of pollination in the canopies of tropical trees or plants in which
flowering is a rare event. I investigate reproductive success as a function of floral
resources, pollinator guilds and the breeding habit in two tree species - Nothapodytes
nimmoniana and Myristica dactyloides, and one monocarpic shrub Strobilanthes
kunthianus, each representing a different forest type in the Western Ghats of India.
Using three distinct approaches, I ask if pressures on the plant populations (from
harvesting of plant resource or habitat degradation) have an impact on pollination
outcomes.
In the two canopies, the pollinator assemblage consisted of small diverse insects with
some degree of specialisation (Coleopterans on Myristica and Dipterans on
Nothapodytes). Bees were abundant in the montane grassland mass bloom of
Strobilanthes, assuring 100% pollination efficiency. There was no pollen limitation in
the three species, but in Nothapodytes, I provide evidence for a shift in insect diversity
and a possible decrease in fruiting in populations where floral density is altered either
naturally or from disturbance. An indirect measure of fruiting success in Myristica
highlighted the influence of non-forest matrix and over-harvesting on mutualisms.
In two species, I examine the evolutionary setting in relation to pollination dynamics:
polygamous individuals seem to guard against decline in mates or pollinators in
Nothapodytes and a set of adaptive floral traits render Strobilanthes protection from
fruiting failure.
I suggest that species with multiple pollinators may not be resilient to fluctuations,
since generalists are just as sensitive to disturbances as specialists. Also, in forest
canopies, there is a frequent overlap of functional guilds: a change in faunal assemblage
could have a cascading effect on pollination processes. Habitat conservation is the key
to maintaining connectivity between pollinator foraging resources that may be located
in different forest types.