Wild native insects are efficient pollinators of mangoes in the Northern Territory of Australia

Abstract

Mango is an economically important fruit crop in tropical regions, including parts of Australia. However, the contribution of native flower visitors to mango pollination and fruit set is currently understudied. We studied cv. Kensington Pride (KP) in the Northern Territory (NT) of Australia to assess the overall contribution of insect pollinators to fruit set through pollinator exclusion treatments – open pollination, total pollinator exclusion and large pollinator exclusion (>5 mm). We also compared diurnal patterns in insect visitation with mango phenology and determined the pollination effectiveness and efficiency of flower visitors based on visitation rates, foraging behaviour and pollen deposition. At 45 days after the first pollinator survey, the number of fruits per panicle in open and large pollinator exclusion treatments was not significantly different from one another, despite large pollinator exclusion panicles receiving less than half of the number of insect visitations. Furthermore, open and large pollinator exclusion treatments had 28- and 30-times higher numbers of fruits per panicle than the total pollinator exclusion treatment, respectively, showing the importance of insect pollination. The native stingless bee Tetragonula mellipes was the most frequent visitor (7906 visits, 62.7 %), followed by a hover fly Mesembrius bengalensis (2404 visits, 19.1 %). Tetragonula mellipes had the highest mango pollen loads on their bodies and deposited more pollen grains on stigmas per visit than other flower visitors, and contributed 75.5 % to the mango pollination services, about 4.5 times more than the next most important pollinator (M. bengalensis: 16.8 %). Our results suggest that T. mellipes efficiently pollinate mango flowers in the NT when wild colonies are abundant in the native vegetation adjacent to the crop. Placing T. mellipes hives in the centre of larger mango orchards may increase pollination services and potentially farm productivity by ensuring good pollination towards the centre of orchard blocks.