Distance and quality of natural habitat influence hawkmoth pollination of cultivated papaya

Abstract

Crop pollination by wild pollinators is an ecosystem service of immense value to modern agriculture. Pollination by wild insects is under-researched in the tropics, where many crops may require or benefit from wild pollinators. Papaya is a dioecious tree crop widely cultivated throughout the tropics. In East Africa, papaya is an important component of rural smallholder farming systems. Traditional agricultural systems are currently under stress due to landscape degradation. These trends are of special concern with respect to pollination services provided by wild insects. Investigation of the role of hawkmoths as pollinators of papaya on subsistence farms in Kenya was conducted over a period of 3 years. Hawkmoths were the most abundant and reliable visitors to both ‘female’ pistillate and ‘male’ staminate papaya flowers. Hawkmoths accounted for >95% of legitimate visits and xenogamous pollination of papaya flowers. Hippotion celerio, Nephele comma and Agrius convolvuli were the main pollinators. Sites in two districts with similar climates and natural vegetation, but different levels of habitat degradation were chosen for comparison of pollinators and pollination services. Hawkmoth abundance and visitation rates declined sharply with increasing distance of natural habitat patches from the crop. Fruit set was also reduced at sites with high levels of disturbance/poor agricultural practices. Natural habitat containing larval food plants and other nectar resources for hawkmoths therefore supports adjacent cultivated papaya with pollination services. Understanding the links between wild biodiversity, in this case pollinating hawkmoths, and agricultural productivity can help bridge the gap between agricultural development and biodiversity conservation.