PhD defence Janet Chik

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Hueng Ying Janet Chik (BPE)

Promotores: Prof. H.L. Dugdale, Prof. S.C. Griffith (Macquerie University), Dr J. Schroeder (Imperial College London)

The evolutionary and ecological drivers of senescence in two wild passerine systems

Senescence (ageing) is a ubiquitous but puzzling phenomenon. If senescence is detrimental, how did it evolve? Why do individuals senesce at different speeds? What environmental factors influence senescence? More importantly, do human-induced environmental deterioration link with senescence and performance in wildlife? This thesis examined how senescence is driven by evolution (genetic inheritance and natural selection) and ecology (environmental stresses), using telomere dynamics as a biomarker. Telomeres are protective DNA sequences that progressively shorten with age and oxidative stress, and short telomeres have been linked with cellular and whole-body senescence, and therefore serve as an important measure bridging physiology and body performance.

The thesis demonstrated, from literature and wild house sparrow data, that telomere length was heritable, and showed genetic variation patterns supporting current evolutionary theories of senescence – that weak natural selection at old age allowed senesced individuals to remain. Evolution via selection was further supported by positive links between telomere length and fitness measures, such as higher survival and lifetime reproductive output, in these sparrows. Concurrently, using data from another house sparrow population under chronic lead pollution, this thesis found that pollution levels impacted telomere length and key survival behaviours. Therefore, there is a need to better understand how environmental deterioration and behaviour impact senescence, in both short and long terms.

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