Optimizing supplementary pollen mixtures for bumblebee Bombus terrestris colonies based on colony reproductive variables
Author of the article:GAI Qin-Bao** ZHOU Zhi-Yong ZHANG Hong HUANG Jia-Xing AN Jian-Dong***
Author's Workplace:Key Laboratory for Insect-Pollinator Biology of the Ministry of Agriculture, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China
Key Words: Bombus terrestris, queenless micro-colony, development traits, principal component analysis, mixture regression model, pollen mixtures
Abstract:
[Objectives] To measure reproductive variables of bumblebee colonies and optimize supplementary pollen mixtures based on these. [Methods] Three types of pollen, apricot (Armeniaca sibirica), willow (Salix caprea), and oilseed rape (Brassica rapa) were mixed following a {3,3} mixture design to obtain seven pollen mixtures. Nine reproductive variables including egg laying delay, larval ejection, total number of larvae, total weight of larvae, total number of pupae, total weight of pupae, duration of the drone stage, total number and birth weight of drones in queen-less micro-colonies of Bombus terrestris (L.) were measured and analyzed in colonies provided with the seven different supplementary pollen mixtures. Principal component analysis was used to assess the information provided by each of the nine variables and pollen mixtures were optimized using the mixture regression model. [Results] To evaluate the micro-colony development of B. terrestris the nine variables can be categorized as either larval development, pupal development, drone development, or developmental cycle, factors (including the total number of larvae, total weight of pupae, birth weight of drones, egg laying delay and duration of the drone stage). Optimized pollen mixtures based on the five representative variables are: 1) oilseed rape pollen for colonies with the shortest egg laying delay, the highest total number of larvae, the greatest total weight of pupae, 2) 1︰1.5︰1.5 combination of apricot︰willow︰oilseed rape pollen for colonies with the shortest drone stage 3) 3︰1 combination of willow︰ oilseed rape pollen for colonies with the largest drone birth weight. [Conclusion] Reproductive variables of B. terrestris micro-colonies can be measured and used to optimize supplementary pollen mixtures. These results should be useful for further research on the nutritional requirements of different developmental phases of bumblebee colonies and for the commercial production of bumblebees.