Ecology and Evolution of Dicistroviridae and Iflaviridae Species Infecting Apis mellifera and Associated Arthropods
Open Access
- Author:
- Levitt, Abby Lynn
- Graduate Program:
- Genetics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 20, 2012
- Committee Members:
- Edward C Holmes, Dissertation Advisor/Co-Advisor
Kelli Hoover, Dissertation Advisor/Co-Advisor
Beth Shapiro, Committee Member
Anthony Paul Schmitt, Committee Member
Christina M Grozinger, Committee Chair/Co-Chair - Keywords:
- Evolution
Virus
Phylogenetics
Viral Ecology - Abstract:
- Honey bees (Apis mellifera), along with other pollinators, make critical contributions to agricultural production and natural ecosystems, with bees pollinating hundreds of wild flowers, weeds, trees and other non-crop plants. Recent widespread declines in overall pollinator populations have become of increasing concern. RNA viruses are suspected as one of the major contributors to honey bee losses, including the recent syndrome referred to as colony collapse disorder (CCD). However, our knowledge of these viral pathogens as they pertain to global distribution or host range is very limited. In this dissertation I investigated the ecology and evolution of some of the RNA viruses found in honey bees as well as in different hymenopteran pollinators and other arthropods associated with A. mellifera colonies. Detection of RNA viruses in thirteen non-Apis hymenopteran species indicated widespread occurrence of these viruses. This study provides 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, the foragers themselves, and non-Apis hymenopteran species, along with subsequent phylogenetic analyses of these viruses, support our suspicion that these viruses are disseminating freely among pollinators and through pollen itself. Phylogenetic analyses also suggest that A. mellifera is the source of introduction at least one virus into the pollinator community -- Israeli acute paralysis virus (IAPV). In addition to viruses detected in foraged pollen, viruses were detected in the pollen and honey stored in the hive and these viruses remained infectious for at least six months of storage. RNA viruses were also widespread among other arthropod members of the ecosystem surrounding honey bee colonies. Viruses detected in this study were found in six orders in Class Insecta (Blattodea, Coleoptera, Dermaptera, Diptera, Hymenoptera, and Lepidoptera) and two orders in Class Arachnida (orders Araneae and Opiliones). Molecular detection of the negative strand of RNA also suggested active replication of virus in some non-honey bee species. This evidence suggests that other species might serve as potential hosts for these viruses, and may be part of the overall chain of transmission. However, further studies are needed to determine if these infections represent a single infection of a new host with no further transmission, such that they are transient spill-overs, or if they are part of a sustained host-to-host transmission cycle within new host populations. Many of these RNA viruses are globally distributed. Although A. mellifera is a managed species that is often moved from one location to another, phylogeographic analysis of at least two of these viruses (black queen cell virus (BQCV), and deformed wing virus (DWV)) show evidence of structured phylogeny by location. This suggests that although variants of theses viruses may have been recently spread through the global trade of honey bees and bee products, the defined structure of both BQCV and DWV phylogeny suggest a long history of infection in the regions examined. This dissertation increases our understanding of RNA virus ecology and evolution and may help explain patterns and emergence of disease in A. mellifera and other potential arthropod hosts.