Two native andrenid bee pollinators face severe population declines in the semi-arid environments of Northwest India

Abstract

Pollinator declines at the global level are the major concern of ecologists. Two ground nesting native andrenid bee species are important part of the pollination services of Northwest India. These include, Andrena savignyi Spinola an important wild pollinator of some major oilseed crops of the family Brassicaseae, and Andrena leaena Cameron an important wild pollinator of some spices crops of the family Umbelliferae, and vegetable crops of the families Brassicaceae, Apiaceae and Leguminoseae. Their importance in the agroecosystems of Northwest India notwithstanding, the actual status of their populations in such habitats is not known. The purpose of this study is to explore the latter aspect of these bees in Northwest India. A survey was conducted on the abundances of two andrenid species foraging on their respective host plants from 1990 to 2015 at an interval of 5 years. I counted the number of foraging bees of the two species on two crops viz. Andrena savignyi on a winter-flowering crop, raya (Brassica juncea) and Andrena leaena on a summer-flowering crop, carrot (Daucus carota). In 25 years, the foraging populations of Andrena savignyi declined from 4.16±0.168 bees/m2 in 1990 to 1.2±0.09 bees/m2 in 2015 and of Andrena leaena from 5.24±0.156 bees/m2 in 1990 to 1.4±0.11 bees/m2 in 2015. This decline in the numbers of foraging bees seemed to be caused by the habitat loss and poisoning of these bees due to the excessive and indiscriminate use of weedicides in the wheat and rice crops grown in this region. Viewing the importance of these bees in the pollination of crops, it is suggested that, habitat of these bees be conserved and, if at all necessary, weedicides safe to the soil nesting bees be used