Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Arts and Sciences



First Advisor

Dr. David Westneat


Organismal traits all exhibit some degree of environmental sensitivity, and both the strength and direction of these phenotypically plastic responses to the environment can evolve in adaptive ways. For example, parents can use information about their own environment to precondition the traits of their offspring so that they thrive in their future environment. This transgenerational plasticity can also alter the plasticity of offspring, but explicit investigations of this specific phenomenon are rare. I begin with a review of the literature and provide a quantitative genetic framework to investigate this phenomenon, which I then explore empirically using avian embryos. The metabolic rate of avian embryos is highly plastic to temperature, and thus, cold conditions cause costly developmental delays. However, evidence from other taxa suggests that ectotherms in cold conditions can modify their metabolic plasticity to temperature. Consequently, I predict that (1) parental effects, such as lay date and incubation behavior, modify avian embryonic metabolic reaction norms through their effects on early thermal conditions, and (2) that these modifications of embryonic metabolism affect growth. First, I analyzed whether parental effects alter embryonic metabolic reaction norms in free-living house sparrows (Passer domesticus). Indeed, both the incubation environment and maternal age influenced embryonic reaction norms and growth. Next, I experimentally tested the effect of incubation temperature on embryonic reaction norms and growth in pekin ducks (Anas platyrhynchos domesticus), which readily develop in laboratory conditions. Contrary to expectations, the incubation environment did not alter embryonic reaction norms. Instead, genetic and/or pre-laying parental effects produced individual differences in metabolic plasticity, which related to post-hatching growth. Finally, I investigated the factors affecting optimal parental incubation by developing a simulation model. I found that optimal incubation was plastic to many environmental factors but was strongly modified by species ecophysiology. Together, these results demonstrate that plastic parental effects do alter offspring reaction norms and fitness. These investigations provide a conceptual and analytical framework for future investigations of this phenomenon. More work is needed to understand how these interactions between parental and offspring environments affect the evolution of plastic traits in an environmentally variable world.

Digital Object Identifier (DOI)

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