Independent Avian Epigenetic Clocks for Ageing and Development

Area of Science:

• Evolutionary biology
• Ecology
• Genetics

Background:

• Accurate age estimation in wild animals is crucial for ecological and evolutionary research.
• Non-lethal methods for age determination are often lacking.
• Biological age can differ from chronological age due to age-related decline, with epigenetic marks like DNA methylation implicated.

Purpose of the Study:

• To develop and validate epigenetic clocks for estimating chronological age in the great tit (Parus major).
• To investigate the relationship between DNA methylation and age-related changes in wild birds.
• To explore the potential of epigenetic clocks in behavioral and evolutionary ecology.

Main Methods:

• Construction of an aging clock using erythrocyte DNA methylation data from 122 post-fledging great tits.
• Development of a developmental clock using DNA methylation data from 67 pre-fledging great tits.
• Validation using a leave-one-out cross-validation approach and analysis of existing brood-size manipulation data.

Main Results:

• The developed epigenetic clocks accurately predicted chronological age with low median absolute deviations (0.40 years for aging, 1.06 days for development).
• Nestlings from reduced broods were estimated to be biologically older than control nestlings, despite expected higher fitness.
• DNA methylation changes at specific CpG sites strongly correlate with chronological age in birds, similar to findings in mammals.

Conclusions:

• Epigenetic clocks provide a reliable, non-lethal method for age estimation in wild birds.
• These clocks offer valuable tools for advancing research in behavioral ecology and evolutionary studies.
• DNA methylation serves as a robust biomarker for aging in avian species.