How Does Pollen Chemistry Impact Development and Feeding Behaviour of Polylectic Bees?

Abstract

Larvae and imagos of bees rely exclusively on floral rewards as a food source but host-plant range can vary greatly among bee species. While oligolectic species forage on pollen from a single family of host plants, polylectic bees, such as bumblebees, collect pollen from many families of plants. These polylectic species contend with interspecific variability in essential nutrients of their host-plants but we have only a limited understanding of the way in which chemicals and chemical combinations influence bee development and feeding behaviour. In this paper, we investigated five different pollen diets (Calluna vulgaris, Cistus sp., Cytisus scoparius, Salix caprea and Sorbus aucuparia) to determine how their chemical content affected bumblebee colony development and pollen/syrup collection. Three compounds were used to characterise pollen content: polypeptides, amino acids and sterols. Several parameters were used to determine the impact of diet on micro-colonies: (i) Number and weight of larvae (total and mean weight of larvae), (ii) weight of pollen collected, (iii) pollen efficacy (total weight of larvae divided by weight of the pollen collected) and (iv) syrup collection. Our results show that pollen collection is similar regardless of chemical variation in pollen diet while syrup collection is variable. Micro-colonies fed on S. aucuparia and C. scoparius pollen produced larger larvae (i.e. better mates and winter survivors) and fed less on nectar compared to the other diets. Pollen from both of these species contains 24-methylenecholesterol and high concentrations of polypeptides/total amino acids. This pollen nutritional “theme” seems therefore to promote worker reproduction in B. terrestris micro-colonies and could be linked to high fitness for queenright colonies. As workers are able to selectively forage on pollen of high chemical quality, plants may be evolutionarily selected for their pollen content, which might attract and increase the degree of fidelity of generalist pollinators, such as bumblebees.

Pollen and nectar quality drive the major and minor floral choices of bumble bees

“…The latter are consistent with previous studies suggesting that amino acid composition is conserved among plant species Weiner et al 2010). High total amino acid content and related nitrogen content have been reported to differ widely among plant species and to be positively correlated with larva weight and development, particularly with more than 20 % total protein content (Génissel et al 2002;Tasei and Aupinel 2008;Vanderplanck et al 2014b). Therefore, the pollen of Comarum palustre and Trifolium pratense might be considered to be of high chemical value, as they showed total amino acid content higher than 20 %, whereas the pollen of Cirsium palustre would be low-quality pollen.…”

“…Studies usually focus on the bumble bee's host plant use and foraging constancy (Carvell et al 2006;Connop et al 2010;Kleijn and Raemakers 2008), or on the pollen nutritive value of several plant species (Hagbery and Nieh 2012;Leonhardt and Blüthgen 2012;Tasei and Aupinel 2008;Vanderplanck et al 2014b). However, the bee's host plant choices coupled with the nectar and pollen quality of host plants have been rarely addressed (Hanley et al 2008;Leonhardt and Blüthgen 2012).…”

The Effects of Pollen Protein Content on Colony Development of the Bumblebee, Bombus Terrestris L.

“…They found that among 10 tested parameters, the most sensitive features to the different pollens were the mean weight of the larvae and the rate of discarded larvae. Similarly, Vanderplanck et al (2014b) found that B. terrestris colonies fed on Sorbus aucuparia and Cytisus scoparius pollen, produced larger larvae and fed less on nectar, compared to the other diets (Salix caprea, Calluna vulgaris, and Cistus sp. diets).…”

Macronutrient ratios in pollen shape bumble bee ( Bombus impatiens ) foraging strategies and floral preferences

“…However, pollen nutritional quality varies widely among plant species, ranging from 2-60% protein and 1-20% lipids by weight (10,18); thus, it likely is critical that bees selectively collect pollen species with the necessary nutritional quality to support their needs (1). The protein and amino acid concentrations of pollen modulate immunocompetence in honey bees (16,19) and reproduction (ovary activation and larval development) in bumble bees (12,14,(20)(21)(22). Furthermore, lipids are key to a variety of physiological processes in insects, including molting hormone production (23), and high sterol content in pollen may increase bumble bee larval size and growth (21).…”

“…The protein and amino acid concentrations of pollen modulate immunocompetence in honey bees (16,19) and reproduction (ovary activation and larval development) in bumble bees (12,14,(20)(21)(22). Furthermore, lipids are key to a variety of physiological processes in insects, including molting hormone production (23), and high sterol content in pollen may increase bumble bee larval size and growth (21). Recently, deficiency in linolenic fatty acid (an essential fatty acid) in honey bees has been linked to reduced learning and development of broodfood-producing glands (24).…”