Bee size increases pollen deposition in Cucurbita maxima (Cucurbitaceae) crops

The study of the performance of animal pollinators has expanded in recent decades mainly due to the concern on crop productivity. Among insects, bees are the main pollinators of most Angiosperm species. The aim of this paper was to study the effect of bee body size on the pollination of Cucurbita maxima Duch. (Cucurbitaceae) var. zapallito crops. We quantified stigmatic pollen deposition by single visits of bee species with different body sizes. Bee species were classified into four categories accordingly to their intertegular distance: Very small (≤ 1.7 mm), Small (1.71 mm < 2.7 mm), Medium (2.71 mm < 3.7 mm) and Large (> 3.71 mm). Fifteen bee species belonging to the Apidae and Halictidae families were observed depositing pollen on the stigmas of C. maxima. The number of pollen grains deposited and the probability of pollen deposition per visit increased significantly with body size. Large bees Xylocopa augusti and Bombus pauloensis were the most efficient species at depositing pollen on stigmas followed by medium-sized bees Eucera fervens and Apis mellifera. The results show that several wild bee species play an important role in the pollination of C. maxima crops. This research provides baseline data for the design of pollination studies to develop strategies to optimize pollination of this crop.