Limitation of complementary resources affects colony growth, foraging behavior, and reproduction in bumble bees

Resource availability has been disturbed for many organisms in agricultural landscapes including pollinator species. Abundance and diversity in flower availability benefit bee populations, however, little is known about which of protein or carbohydrate resources may limit their growth and reproductive performance. Here, we test the hypothesis of complementary resource limitation using a supplemental feeding approach. We applied this assumption with bumble bees (Bombus terrestris), assuming that colony growth and reproductive performance should depend on the continuous supply of carbohydrates and proteins, through the foraging for nectar and pollen respectively. We placed wild-caught bumble bee colonies along a landscape gradient of semi-natural habitats, and monitored the colonies’ weight, foraging activity and reproductive performance during the whole colony cycle. We performed supplemental feeding as an indicator of landscape resource limitation, using a factorial design consisting of...