Assessing the impacts of environmental change on British pollinators (Syrphidae) using next generation sequencing techniques

Abstract

British pollinating insects are vital for their contribution to crop yields as well as maintenance of semi-natural environments across the UK. The Syrphidae family are highly diverse and thought to be an important pollinating group. In order to understand the evolutionary relationships in this family, mitochondrial genomes were used to build the largest tree of the Syrphidae family to date. This tree was used to establish relative ages for divergences within the family, and to explore the evolution of diverse syrphid larval life histories. The recent introduction of a UK pollinator monitoring programme has resulted in a large amount of data with the potential to inform conservation and management, presenting an opportunity for DNA analysis. A CO1 reference database was curated and tested for UK syrphids, resulting in sequences for 70% of UK species and highlighting difficulties in DNA identification. Barcoding of syrphids was then expanded by also metabarcoding pollen from gut samples. This showed the diversity of plant – syrphid interactions at an individual level across three different land use types. It also highlighted the importance of including syrphid larval life histories in analyses of this family, as these appeared to have a larger effect on species composition than pollen composition did. Finally, the reach of this thesis was expanded to include non-bee and non-syrphid pan trap visitors from the pollinator monitoring programme. This highlighted the diversity of non-syrphid Dipterans and allowed species and phylogenetic diversity to be compared in these bulk insect samples. Using DNA methods to analyse monitoring data has the potential to increase our knowledge of cryptic species, phylogenetic diversity and pollinator associations. Alongside this, DNA can be used to analyse large datasets of diverse pollinating insects which otherwise would be overlooked.