Date of Award

2013

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biological Sciences

First Advisor

Heath, Daniel D.

Second Advisor

Hubberstey, Andrew

Keywords

Biological sciences, Adaptation, Adaptive responses, Dispersal, Ecotoxicogenomics, Genetranscription, Physiological acclimation

Rights

CC BY-NC-ND 4.0

Abstract

Organisms are likely to display adaptive responses to their local environment, it may be local adaptation or physiological acclimation, and both improve performance (increase fitness) in stressful habitats. In this dissertation, I explore adaptive responses to pollution stress in the brown bullhead ( Ameiurus nebulosus ) from the Detroit River, as a model for integration of evolutionary and ecotoxicologial analyses. I develop a systematic hierarchical scheme to investigate the role of adaptive processes in response to stressful environments. My literature-based review suggests initial investigation of dispersal as confounding adaptive response to degraded local environment. If there is low dispersal I suggest variation in gene transcription as a biomarker for accurate and repeatable measures of the response to pollution stress, as gene transcription is a very early response to contaminant stress. Following my proposed approach, I examined dispersal and molecular adaptive responses in brown bullhead and developed tools for the analyses: population genetic markers, a custom microarray and transcriptome libraries. The population genetic study demonstrates high population structure F ST = 0.095 indicating limited long-term gene flow but contemporary dispersal associated with high contaminant levels (37% dispersals within each region). My initial transcriptome characterisation was done with next generation sequencing (NGS) on challenged and control individuals from two sites (degraded and clean). The NGS transcriptome characterisation was resulted in 3.4 million assembled reads and identified 5515 transcribed genes across clean and polluted background populations. Many gene transcription patterns were as expected as part of an adaptive response; however, some expected transcription induction was not observed. Thus I used a 128 gene custom ecotoxicology response microarray to quantify dose and temporal response of selected genes in brown bullhead exposed to B[a]P. This identified 5 up-regulated and 5 downregulated gene responses: up-regulation included a variety of response profiles, while down-regulation was simple gene repression. All forms of adaptive responses in contaminant indicator species have the potential to confound our interpretation of toxicity in natural and lab environments. This may have important management and legislative implications. Of equal interest, my thesis research highlights some behavioural and molecular mechanisms for adaptive responses in Detroit River bullhead.

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