Pollinators, pollination efficiency and fruiting success in a wild nutmeg, Myristica dactyloides.

We investigated the pollinator assemblage in Myristica dactyloides, a dioecious tree species occupying the intermediate canopy stratum of the mid- and high-elevation wet evergreen forests and endemic to Sri Lanka and the Western Ghats of India. We surveyed two populations and, in one of them, marked four male and three female trees for observations on floral display and insect foraging, and two female trees for experimental pollination. Yellow sticky traps were used to sample insects in the canopy during the flowering season of December 2007 in addition to direct observations of insect activity in 2006. Myristicaceae members from other tropical areas have been reported to be specialized to beetle pollination, but our observations provide evidence of a generalist pollination system in M. dactyloides, composed of small, diverse insects: thysanopterans (thrips), coleopterans (beetles), halictid bees and dipterans (syrphid and phorid flies). Quantifying floral display, we found that female inflorescences were smaller, offered no reward and attracted significantly fewer pollinators in comparison to male inflorescences. Fruit set was low and could be attributed to a 29% flower abscission and abortion of young fruits, but a reasonably high natural pollination efficiency combined with pollination experiments established that there was no pollination limitation in the study population.