Ecological and Evolutionary Interactions between Fruitflies and Their Parasitic Wasps Open Access

Milan, Neil F (2012)

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My dissertation project focuses on the evolution and ecology of the Drosophila-
wasp parasitoid system, particularly the fruitfly D. melanogaster and wasps of the
genus Leptopilina. The parasitoid wasps use an ovipositor to
inject eggs into fruitfly larvae or pupae. At that point, there is a competitive, within
host interaction between the fruitfly's immune response and the wasp egg invader.
The immune response attempts to surround and kill the egg so that the fruitfly can
complete its development; the wasp egg invader, in contrast, attempts to develop
and emerge as a larva quickly enough to evade the immune response, consume the host from the inside-out and develop into an adult wasp. The first
research area is the effect of ethanol on the interaction between the fruitfly host and
wasp parasitoid. While so much of the host-parasite interaction can be (and is)
affected by the genotypes of the fruitfly and wasp, the surrounding environment in
which the two interact also crucially affects attack rates, immune system evasion
and wasp development. I have been particularly interested in how the host-parasite
dynamic changes when wasp parasitoids encounter fruitflies that feed on food
plants that contain toxins to which the flies are resistant, but which may be toxic to
the parasitoid. My work indicates that the presence of ethanol does limit wasp
attack, hinders wasp infection success, and induces a "self-medication" behavior in
parasitized fly larvae. The second research area is the horizontal gene transfer of
transposable elements between fruitflies and their wasp parasitoids. Although the
traditional view once held that genes are passed on only from parents to offspring,
the last few decades have seen numerous reports of horizontal gene transfer
between higher eukaryotes, including multicellular animals. Since hosts and
parasites have very strong intimate associations, it can be hypothesized that there
should be high rates of gene transfer between these organisms. Indeed, using the
Drosophila-wasp parasitoid system I have found evidence for high rates of
horizontal gene transfer, which is an exciting development for evolutionary
biologists in particular because it may shed light on how novelty evolves within
genomes and populations.

Table of Contents

Chapter Item - Page

1. Dissertation Introduction - 1

2. "Alcohol Consumption As Self-Medication Against Parasites In The Fruitfly" - 12

Figure 1 - 34

Figure 2 - 36

Figure 3 - 38

Figure 4 - 40

Figure 5 - 42

Figure 6 - 44

Figure 7 - 46

Manuscript Acknowledgements - 49

3. "Extensive horizontal gene transfer between Drosophila melanogaster and its endoparasitoid wasps" - 50

Table 1 - 67

Table 2 - 68

Table 3 - 69

Figure 1 - 70

Figure 2 - 72

Figure 3 - 74

Figure 4 - 76

Figure 5 - 78

Figure 6 - 80

Supplemental Figure S1 - 82

Supplemental Figure S2 - 84

Supplemental Figure S3 - 86

Manuscript Acknowledgements - 92

4. "Phylogenetic Analysis of Two TEs in Drosophila and Their Wasp Parasitoids Reveals an Interaction Highly Permissive to Horizontal Transfer But Unlikely TE Adaptation in Novel Hosts" - 93

Figure 1 - 105

Figure 2 - 107

Figure 3 - 109

Figure 4 - 111

Figure 5 - 113

Figure 6 - 115

5. Dissertation Discussion - 117

6. Bibliography - 132

About this Dissertation

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