Differential reproductive success in Cassia fistula in different habitats — A case of pollinator limitation?

• Published in: Current science (Bangalore) Vol. 65; no. 3; pp. 270 - 272
• Main Author: Murali, K. S.
• Format: Journal Article
• Language: English
• Published: Current Science Association 10-08-1993
• Subjects: Bees; Cassia fistula; Fistulas; Flower stigma; Inflorescences; Insect pollination; Plants; PLANT–POLLINATOR INTERACTIONS; Pollen; Pollinating insects; Reproductive success; Trees; India
• ISSN: 0011-3891

Differences in flower success patterns in two habitat types that differed drastically with respect to rainfall, tree density and species composition were studied at Mudumalai wildlife sanctuary, India. Observations on phenological patterns of two species, Cassia fistula and Gmelina arborea, were made from April 1988 through June 1990. Quantitative data on flower–fruit ratio, insect visitation rates, pollen grain per stigma and the number of fruits per tree were recorded. Data were also collected on the number of pollen deposited on the stigma after different types of bees visited the flower. The data suggested that only carpenter bees (Xylocopa spp) effect pollination in C. fistula. The differences in fruit–flower ratios were attributed to the differences in insect visitation rates to inflorescences between sites. The low pollen number per stigma and the resultant reduction in reproductive success in C. fistula are attributed to the competing species G. arborea receiving more visitations from pollinators in the wetter site. These results suggest that pollinator limitation is another constraint in reproductive success of plants.