ECOLOGY AND EPIDEMIOLOGY OF RNA VIRUSES IN HYMENOPTERAN POLLINATORS
Open Access
- Author:
- Singh, Rajwinder
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 20, 2011
- Committee Members:
- Edwin George Rajotte, Dissertation Advisor/Co-Advisor
Edwin George Rajotte, Committee Chair/Co-Chair
Diana Lynn Cox Foster, Committee Chair/Co-Chair
Frederick Eugene Gildow Jr., Committee Member
Edward C Holmes, Committee Member
Rosalind James, Committee Member - Keywords:
- RNA viruses
pollinators
honey bees
bumble bees
alfalfa leafcutting bees
Apis mellifera
Bombus impatiens
Megachile rotundata
pathology
virology
DWV
IAPV
Picorna-like viruses - Abstract:
- Pollinators are critical to agricultural production and maintenance of natural plant communities. However, widespread declines in pollinator populations have become a cause of concern. RNA viruses are suspected as one of the major contributors to honey bee (Apis mellifera) losses including the recent malady, colony collapse disorder (CCD). But, our knowledge of viral diseases in other managed and wild bee species is very limited. This dissertation investigates the ecology and epidemiology of RNA viruses in different hymenopteran pollinators. Detection of RNA viruses in thirteen non-Apis hymenopteran species, using reverse transcriptase-PCR, indicated widespread occurrence of these viruses. This study provides the first evidence of pollen as a route of inter-taxa transmission of RNA viruses in hymenopteran pollinators. Molecular detection of viruses in pollen pellets from foragers and the subsequent phylogenetic analyses support that these viruses are disseminating freely among the pollinators via the pollen itself. The viruses in the pollen and honey stored in the hive were demonstrated to remain infectious for at least six months of storage. RNA viruses were also widespread in commercial colonies of the bumble bee, Bombus impatiens, the major pollinator of greenhouse crops, but were less prevalent in the alfalfa leafcutting bees (ALCB) (Megachile rotundata) and the alkali bees (Nomia melanderi), the two solitary bees essential for the alfalfa seed crop. Inter-taxa transmission of one of these viruses was further demonstrated in containment greenhouse experiments, where the recently described Israeli acute paralysis virus (IAPV) moved between honey bees and bumble bees within ten days. IAPV disseminated throughout the bee body including the ovaries and eggs when fed to virus-free bumble bee queens, but remained restricted in the gut of the ALCB larvae. IAPV infection negatively impacted the health of bumble bee and honey bee colonies under greenhouse conditions, and adult survivorship and larval diapause in ALCB laboratory bioassays. However, further studies are needed to understand the role of IAPV and related viruses in the recent declines in field populations of different pollinators. This study increases our understanding of RNA virus ecology and epidemiology and may help explain bee disease patterns and pollinator declines in general.