Pollination Entomology in West Coast Mangroves of South India

Mangrove forests stand as sentinels in the seashores of equatorial and tropical coasts, contributing to the ecological and economic security of mankind. Insects play diverse roles and assist in ecosystem processes, among which their role as pollinators is the most noteworthy. Baseline data on insects associated with pollination of select dominant mangrove species of the coastal tracts of Karnataka were generated. Thirty-six insect species on bloom foraging species were categorized in 18 families belonging to four insect orders and were recorded. Flower visiting insects were collected from three species, Avicennia officinalis L., Rhizophora mucronata L., and Sonneratia caseolaris (L.) Engler. Different species of flower frequenting pollinators and foraging sorties were recorded under field conditions. Based on the characteristics of insects and blooms, an effort was undertaken to compare the dominant pollinators from the just-flower-frequenting pollinator guild of mangroves. The flowering period of R. mucronata occurred from February to July in coastal Karnataka. S. caseolaries start flowering in October and the flowering season lasts up to May. Research showed that S. caseolaries and A. officinalis offer both nectar and pollen to the pollinators. In R. mucronata flowers, no nectar was found. A profuse amount of pollen was produced as reward in this species. Reproductive biological experiments revealed that A. officinalis reproduced through cross and selfing, with preference for cross-pollination. Field pollination biology experiments in R. mucronata showed self-pollination mode. Insect exclusion resulted in less fruit set (ca 5%) in S. caseolaries. This study highlighted interesting interactions and relationships of insects with plants in the mangrove ecosystems of the west coast of India.