Environmental context matters: studies of variation in developmental life-history traits in insects Open Access
Couret, Jannelle (2014)
Abstract
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
About this Dissertation
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Supplemental Files
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