Foraging ecology and conservation of honeybees, bumble bees and solitary bees

Hennessy, Georgia (2021) Foraging ecology and conservation of honeybees, bumble bees and solitary bees. Doctoral thesis (PhD), University of Sussex.

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This thesis contributes to two inter-related fields of research: bee conservation and bee foraging ecology. The first focuses on solitary bee ecology, identifying forage and habitat requirements along with educating the general public on aspects of solitary bee behaviour to aid in the conservation of the studied species. These results greatly improve our understanding of two rare and understudied species of solitary bee in the UK, Eucera longicornis, the long-horned bee, and Anthophora retusa, the flower potter bee, along with information on the forage requirements of a common and non-native bee species, Colletes hederae, the ivy bee, confirming its specialisation and reliance on the plant species Hedera helix, common ivy. The information provided by this research on the two rare species is currently being used by stakeholders to help conserve populations found on their land. The second focuses on how an important but understudied environmental factor, wind, influences bee foraging behaviour. Two types of common social bees, honey bees and bumblebees, that are major pollinators were studied foraging on both artificial and natural flowers, with implications for increasing our understanding of the potential future impacts of climate change on bees. Among other things, the wind research has identified a novel part of foraging behaviour much influenced by wind, hesitancy to take-off from flowers, which increases at higher wind speeds, and results in significant decreases in flower visitation rate. This thesis has contributed novel knowledge to our understanding of the foraging ecology of two rare bee species in the UK and has identified that having a wide foraging breadth does not necessarily mean a species will be common, as was found to the case for A. retsua. Foraging behaviour was also found to be influenced by the understudied environmental variable, wind, with it being found to reduce the foraging efficiency of honey bees and increase both honey bees and bumble bees hesitancy to take off.

Chapter Two studied the population of the rare solitary bee, Anthophora retusa, living at Seaford Head in Sussex, one of the 5 sites it is known from in Britain. Results showed that it forages on a range of flower species, including the very common Glechoma hederacea (ground ivy). The population is small (male population size in 2019 was estimated to be around 160 individuals). Transect surveys showed that the species is restricted to a very small area, c. 30ha area within the Seaford Head reserve.

Chapter Three shows that the two populations of the rare Eucera longicornis found on Gatwick Airport land had estimated populations of 300 females and 130 males in 2019, and that these populations remained approximately stable over the three years of data collection. Eucera longicornis females collected pollen predominantly from species within the Fabaceae family, which were highly abundant within the 500m surrounding the aggregations and hence are likely to be key to their success.

Chapter Four confirmed that ivy, Hedera helix is the predominant floral resource for the solitary bee, Colletes hederae (ivy bee) in Sussex, with ivy comprising 98% of pollen samples collected from females. Female C. hederae activity was synchronised with ivy bloom. However, C. hederae females did collect pollen from other plant species before ivy was in peak bloom. C. hederae was the most abundant species foraging on ivy, even when honeybee hives were present in the local area.

Chapter Five used artificial flowers and wind generated by fans and found that increasing wind speed caused a significant reduction (37%) in flower visits for foraging Apis mellifera. This reduction was due to an increase in ‘hesitancy’, the time to take off from a flower once a bee had finished probing. The indirect effect of flower movement had no effect on flower visitation rate. However, it did cause an increase in flight duration but this was offset by a decrease in search time once a bee was on a flower.

Chapter Six found that when foraging on natural flowers of lavender and marjoram Apis mellifera flower visit rate decreased with increasing wind speed due to an increase in handling time per flower. The influence of wind speed on flower visit rate differed between lavender and marjoram, with a sharper reduction when foraging on marjoram. This was not explained by differences in flower movement speed, with flower movement not influencing flower visit rate.

Chapter Seven found that when foraging on lavender, Apis mellifera flower visit rate decreased with wind speed, whereas Bombus species flower visit rate was unaffected. However, both species did experience an increase in handling time per flower with increasing wind speed. Also, the number of Bombus foragers on a patch with wind was significantly lower than on a patch where no wind was present, indicating when given the option they will choose to forage in lower wind speeds.

Chapter Eight identified that hesitancy to take off increased with wind speed for both Apis mellifera and Bombus species when foraging on seven plant species in naturally varying wind conditions. Hesitancy duration in relation to wind speed did not differ between plant species. However, independently of wind speed it did. Bombus hesitancy was found to increase significantly more with increasing flower movement when compared to A. mellifera.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QL Zoology > QL0360 Invertebrates > QL0434 Arthropoda > QL0463 Insects > QL0563 Hymenoptera > QL0568.A-Z Systematic divisions. By family, A-Z > QL0568.A6 Apidae (Bumblebees; honeybees; stingless bees)
Depositing User: Library Cataloguing
Date Deposited: 25 Aug 2021 08:10
Last Modified: 25 Aug 2021 08:10

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