Environmental context matters: studies of variation in developmental life-history traits in insects Open Access

Couret, Jannelle (2014)

Permanent URL: https://etd.library.emory.edu/concern/etds/vt150j378?locale=en


Life history traits influence the survival and reproduction of organisms. They can

vary across organisms based on previous response to selection and based on plastic responses

to abiotic and biotic factors. Here, I examine how life history traits of insects vary in

response to environmental conditions and in response to association with microbial

symbionts. I introduce life-history theory and traits, how traits vary in response to

environment, and the biological systems used in this dissertation. I then use a meta-analytic

statistical approach to estimate the variation in life-history traits of the species within the

Culex pipiens complex. I demonstrate that the temperature of the developmental habitat is a

more significant explanatory factor for development rate variation than sub-species identity.

The effect of temperature, however, is heterogeneous and the residual variation in

development rate is best explained by two factors, density and study methodology. I repeat

this approach in another species, Aedes aegypti, where environmental context of temperature

alone is sufficient to explain development rate variation. To test the results, I assess the

impact of three environmental factors over a wide range of values on development in Ae.

aegypti. Using this empirical approach, I demonstrate that temperature, diet, and density

interact to explain developmental life-history traits. I also found that the effect of temperature

is mediated by the context of diet and density. Finally, I experimentally consider the impact

of an obligate microbial symbiont on development and survival in a hemimetabolous

stinkbug reared on two alternative plants. I show that host plant context mediates the impact

of symbiosis on its stinkbug host's development. These studies illustrate that environmental

context matters for life-history trait variation. The phenotypic expression of these traits is

contingent on multiple environmental factors both abiotic and biotic.

Table of Contents

Chapter 1: Introduction

1.1 Variation in life-history traits 1

1.2 Environment and life-history trait variation 4

1.3 Environment and symbiosis 5

1.4 Mosquito study systems 7

1.5 Megacopta cribraria study system 10

Chapter 2: Variation in development rate and survival in Cx. pipiens s.l.

2.1 Introduction 13

2.2 Methods 16

2.3 Results 20

2.4 Discussion 30

Chapter 3: Variation in development rate and survival in Ae. aegypti

3.1 Introduction 36

3.2 Methods 39

3.3 Results 43

3.4 Discussion 53

Chapter 4: Study of the interactive effects of the developmental environment on Ae. aegypti life-history traits

4.1 Introduction 61

4.2 Methods 63

4.3 Results 66

4.4 Discussion 74

Chapter 5: Impact of obligate microbial symbiont on invasive stink bug Megacopta cribraria is mediated by the context of host plant

5.1 Introduction 79

5.2 Methods 83

5.3 Results 89

5.4 Discussion 94

Chapter 6: Conclusion 101

References 106

Appendix I: Supplemental tables

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