Pollination Ecology of Rocket (Eruca vesicaria (L.) Cav. ssp. sativa (Mill.) Thell) in the Semi-Arid Environments of Northwest India: Native Bees Are the Major Pollinators

Abstract

Several insect species visit the flowers of a plant to obtain floral rewards in the form of pollen and/or nectar. In return, we would anticipate that those visitors would contribute to the reproductive success of the plant. Do these visitors contribute equally towards the reproductive success of the plant? This issue has been the interest of many pollination ecologists. To find a solution to this problem, I investigated the pollination ecology of rocket (Eruca vesicaria (L.) Cav. ssp. sativa (Mill.) Thell), an important leafy vegetable used as salad. I captured the flower visitors with a hand net from the experimental field and had these identified. I also recorded the number of loose pollen grains carried on the body of the visitors of different species and deposited on the stigmas. Effects of single and multiple visits of visitors on the seed set of rocket flowers were also determined. Abundances and foraging rates of the flower visitors of this species were recorded and their values were used to calculate their respective contributions towards the reproductive success of this species. Five species of Hymenoptera, three of Diptera, one of Lepidoptera, and one of Coleoptera visited the flowers of the rocket. Apis florea was the most abundant among the flower visitors, followed by the dipterous flies, Apis mellifera, Apis dorsata, Andrena savignyi, and Andrena leaena in descending order. The number of loose pollen grains carried and deposited, foraging behaviors, foraging rates, and abundances did not provide conclusive measures to differentiate the contributions of different flower visitors towards the reproductive success of the rocket. However, the data recorded on abundances, foraging behaviors, and foraging rates together could do so. Accordingly, Andrena savignyi was the most efficient pollinator of rocket, followed by Andrena leaena, Apis dorsata, Apis mellifera, and Apis florea; dipterous flies were the least efficient pollinators of this plant species. In rocket, 28.84% of pollination was brought by Andrena savignyi, 24.69% by Andrena leaena, 20.34% by Apis dorsata, 18.37% by Apis mellifera, and 7.7% by Apis florea; dipterous flies caused only 0.06% pollination. Butterflies were very rare and Coccinella sp. was not a pollinator of this plant. Therefore, not all the pollinators of rocket contributed equally towards its reproductive success (seed production). Bees brought about 99.94% of total pollination and melittophily distinctly predominated over other pollination modes. However, among the bees, native bees together are the major pollinators in the flowers of rockets and accomplished more than 81.5% pollination. Therefore, the conservation of native bees is most important for the pollination of crops such as rockets.