Parasite Insight: Apicystis bombi Prevalence of the under-reported parasite Apicystis bombi across natural barriers and life stages in pollinator hosts.
Date: 20 January 2020
University of Exeter
Masters by Research in Biological sciences
Annually, bees contribute over US$298 billion to the world economy, mostly through their ecosystem service of pollination. Several anthropogenic effects are reducing global wild and managed bee species populations, such as climate change and agricultural land use. There is an urgent need to fully understand the causes of these declines ...
Annually, bees contribute over US$298 billion to the world economy, mostly through their ecosystem service of pollination. Several anthropogenic effects are reducing global wild and managed bee species populations, such as climate change and agricultural land use. There is an urgent need to fully understand the causes of these declines in order to find lasting solutions. One important factor in these declines caused by these anthropogenic effects may be emerging bee pathogens. Bee pathogens can easily jump when transmitted oral-fecally between species due to shared food resources and the commercial movement of honeybee and bumblebee hives. Bees typically have less resistance to emerging pathogens which they have not evolved alongside of, compared to established pathogens, potentially making emerging pathogens a major contributor to bee declines. This thesis studies the spread of the largely under-researched neogregarine parasite Apicystis bombi, which has been shown to have lethal and sub-lethal effects on bumblebees. Island biogeography predicts that islands have a lower prevalence of pathogens compared to nearby mainland. Chapter 2 compares the prevalence of A. bombi in the UK and France across island and mainland sites in foragers of two bumblebee species, Bombus terrestris and Bombus pascuorum, and the honeybee, Apis mellifera. The island prevalence of A. bombi in B. terrestris (41%±3 s.e.) and B. pascuorum (30%±3) was significantly lower than nearby mainland sites (65%±7 and 65%±9), despite having similar climates. This suggests that natural barriers significantly slows the spread of pathogens. However, in A. mellifera the island prevalence (65%±5) of A. bombi was as high as the mainland prevalence (63%±5). A possible explanation is that the commercial transportation of honeybees bypasses natural barriers, spreading pathogens. The distribution of A. bombi in A. mellifera hives has never been reported before. Chapter 3 investigates the prevalence of A. bombi across A. mellifera capped larvae, nurses and foragers. All three life stages contained A. bombi, although larvae (59%±10) and foragers (63%±15) had a significantly higher prevalence than nurses (23%±12), confirming that A. bombi can be spread throughout the hive either by contaminated pollen or faeces. The A. bombi prevalences found here are much higher than previously reported, in both A. mellifera and Bombus species. Such high prevalence is cause for concern, and could be a contributing factor in global bee declines.
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