Genetics and human management in Varroa destructor parasitism Restricted; Files Only

Dynes, Travis (Summer 2018)

Permanent URL: https://etd.library.emory.edu/concern/etds/zs25x850z?locale=en
Published

Abstract

European honey bee colonies have experienced widespread losses in the past decades, a particular concern due to the importance that honey bees play in agricultural services critical in both economic terms and to human health. In the first half of the 20th century the obligate ectoparasitic mite Varroa destructor made a sustained host switch from the Asian honey bee to the European honey bee. Since that time V. destructor has spread around the world and become the largest pathogenic threat currently facing the beekeeping industry.

 

When Varroa arrived in the United States in the 1980’s beekeepers were able to effectively treat Varroa infections with miticides. However, the mites quickly developed resistance to these miticides. This was unusual considering Varroa is characterized by a lack of genetic diversity. Our research was able to show that there was more genetic diversity at fine scales than would have been predicted. This implies that there was also more transmission of mites between colonies than would have been predicted. Human management of honey bee colonies places colonies in densities that more than three orders of magnitude greater than would be found in feral colonies. This increased density has implications for parasite transmission, colony health and survival. We found that increased density leads to more potential for disease transmission, decreased colony health and productivity, and increased winter mortality.

 

According to the virulence-transmission theory, Varroa populations evolving under these different management intensities (from feral to heavily managed) may face different selection pressures for population growth and virulence. Our research was consistent with this hypothesis for population growth. However, our virulence results suggest that there are genotype by genotype interactions that are occurring.

Table of Contents

Chapter 1

1.1  Introduction                                                                                                                                            1

 

Chapter 2: Fine scale genetic structure of Varroa destructor, an ectoparasitic mite of the honey bee (Apis mellifera)

2.1 Introduction                                                                                                                                6

2.2 Materials and Methods                                                                                                               8

2.3 Results                                                                                                                                      11

            Table 2.1 Population (apiary) pairwise FST values                                                             13

            Table 2.2 AMOVA analysis                                                                                               14

            Figure 2.1 Fine scale allelic diversity compared to global allelic diversity                       15

            Figure 2.2 Allelic diversity in ten apiaries using a rarefaction approach                           16

            Figure 2.3 AMOVA change in source of population variation over time                          16

2.4 Discussion                                                                                                                                17

2.5 Supplementary Materials                                                                                                          22

            Table 2.S1 Observed and expected heterozygosity levels within apiaries                         25

            Table 2.S2 Observed and expected heterozygosity levels within colonies                        26

            Table 2.S3 SMOGD alternative estimates of population differentiation                            27

            Figure 2.S1 Boxplot of Garza-Williamson Index values                                                   28

 

Chapter 3: GRAPHITE: A graphical environment for scalable in situ video tracking of moving insects

3.1 Introduction                                                                                                                               29

3.2 Experimental Setup                                                                                                                  32

            Figure 3.1 Camera housings                                                                                               33

3.3 Modules and Editor                                                                                                                   34

            Figure 3.2 Analysis pipeline                                                                                               35

            Figure 3.3 Active region                                                                                                     36

            Figure 3.4 Tag detection from a single video frame                                                           38

            Figure 3.5 Tag tracks                                                                                                          41

            Figure 3.6 Graphical user interface                                                                                     42

3.4 Evaluations                                                                                                                                43

3.5 Conclusions and Future Directions                                                                                           44

3.6 Supplementary Material                                                                                                            45

            Figure 3.S1 Tagged bees                                                                                                    45

            Figure 3.S2 Editor                                                                                                               45

 

Chapter 4: Reduced density and visually complex apiaries reduce parasite load and promote overwintering survival in honey bees

4.1 Introduction                                                                                                                               46

4.2 Materials and Methods                                                                                                             49

            Figure 4.1 Scale representation of apiary arrangement from above                                   50

4.3 Results                                                                                                                                      55

            Figure 4.2 Honey production over time                                                                             56

            Figure 4.3 Mite count by sticky board                                                                               57

            Figure 4.4 Mite levels in brood                                                                                          58

            Figure 4.5 Survival curves and winter survival                                                                  59

            Figure 4.6 Representation of drift within each of the apiaries                                           60

4.4 Discussion                                                                                                                                61

 

Chapter 5: Assessing virulence of Varroa destructor mites from different honey bee management regimes

5.1 Introduction                                                                                                                               67

5.2 Materials and Methods                                                                                                             70

            Table 5.1 Mite inoculation sources within each apiary                                                      71

5.3 Results                                                                                                                                      76

            Figure 5.1 Measures of mite abundance by treatment                                                       76

            Figure 5.2 Number of frames of brood by treatment                                                         78

            Figure 5.3 Survival curves by mite treatment                                                                    78

5.4 Discussion                                                                                                                                79

 

Chapter 6

6.1 Dissertation Conclusion                                                                                                            85

 

Bibliography                                                                                                                              88

About this Dissertation

Rights statement
  • Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.
School
Department
Subfield / Discipline
Degree
Submission
Language
  • English
Research field
Keyword
Committee Chair / Thesis Advisor
Committee Members
Last modified No preview

Primary PDF

Supplemental Files