Land use and season interactively affect honeybee (Apis mellifera) body
size and fat stores
Abstract
The loss and fragmentation of habitats caused by anthropogenic
activities in the last decades has affected foraging habitat quality
and, therefore, foraging success (food quantity, quality and foraging
range) of many animals, including many pollinators. Honeybees (Apis
mellifera) are important pollinators of many plant species, and habitat
change has also affected their ability to collect the resources they
need to maintain the colony. Two important biological traits that might
be affected by land use are body size and fat stores, which have the
potential to affect body condition, and therefore success, and colony
health. However, few studies have investigated these traits in different
landscapes and different times of year. We surveyed 47 sites in three
different landscape types (agriculture, urban and mixed habitats) in
south-western Germany. We measured honeybee body size, wing wear and
analysed body fat quantity and composition using GC-MS in the spring,
summer and autumn. We found that summer honeybees were smaller in urban
and mixed habitats, they showed the greatest wing wear, but they had
18.4-21.3% larger fat stores compared to agricultural sites. Bees in
agricultural habitats experienced a drop in fat stores in summer, while
body size remained unaffected. In autumn, just before honeybees enter
the inactive winter period, bees in urban and mixed areas experienced a
drop in fat stores. Wing length decreased from spring to autumn
irrespective of habitat type. Our findings indicate that bees in
agricultural settings experience physiological challenges in a central
European region in summer, possibly because urban and mixed habitats
provide better nutritional conditions during summer. Our findings, thus,
confirm that honeybees undergo morphological and physiological changes
in response to land use and season, which could impact their
physiological condition and winter survival.