Diversity and foraging behaviour of floral visitors assemblages in onion Allium cepa L.

Anthophilous insects are of key importance for onion reproduction due to the protandrous nature of flowers, related to inbreeding avoidance. We documented the diversity of floral visiting insects on onion flowers at the ICAR-Indian Institute of Horticultural Research, Bengaluru, Karnataka, India, during 2019-21. The pollinator community is composed of thirty hymenopteran species, sixteen dipteran species, eight lepidopteran species, four hemipteran species, and one species from Coleoptera. From these, Hymenoptera and Diptera contributed >75% of the floral visitors. The majority of the floral visits by the anthophilous insects were for collecting nectar (81.59%) followed by nectar as well as pollen foraging (9.97%) and only pollen (8.44%). The proportion of stigma contact did not depend on the body size of the floral visitor. However, stigma contact depends on whether floral visitors collected nectar or pollen and also on the head width of the floral visitor. The present study helps to understand the pollination efficiency of pollination candidates for onion. Further, there is a need to study the pollen harvest and effective stigmatic pollen deposition by the floral visitors.由于洋葱花具有雄性先熟的特性，该特性与避免近交密切相关，因此嗜花昆虫（anthophilous insects）对洋葱繁殖至关重要。本研究于2019-2021年间，在印度卡纳塔克邦班加罗尔的ICAR-印度园艺研究所开展，对洋葱花上的访花昆虫多样性进行了详实记录。该传粉者群落共包含30种膜翅目昆虫、16种双翅目昆虫、8种鳞翅目昆虫、4种半翅目昆虫，以及1种鞘翅目昆虫。其中膜翅目与双翅目昆虫占访花昆虫总量的75%以上。嗜花昆虫的多数访花行为以采集花蜜为主（占比81.59%），其次为同时采集花蜜与花粉（9.97%），仅采集花粉的行为占比为8.44%。访花昆虫的柱头接触比例并不随其体型大小发生变化，但却与昆虫的采集行为（采集花蜜或花粉）以及头部宽度显著相关。本研究有助于明确洋葱潜在传粉者的传粉效率，后续仍需针对访花昆虫的花粉采集量及其有效柱头花粉沉积量展开深入研究。