Physiology of life histories and senescence
What reproductive strategies individuals use to maximize their fitness is the central topic of the study of life-history evolution. Advances in molecular genetic techniques and the increased availability of long-term datasets facilitate the study of previously ignored aspects of life-history evolution, such as senescence and the role of hormones. We use blue tits and Seychelles warblers as model organisms to study the evolution of senescence and the role of hormones in shaping life histories in natural populations.
Senescence is the progressive decline in physiological and cellular function with age. Until recently, it had been assumed that wild animals suffer from extrinsic mortality (e.g. due to predation) before they experience the deleterious effects of senescence. However, several recent studies in natural populations showed senescent declines in reproduction and survival, but the extent and causes of individual variation in senescence remain largely unexplored. Using the Seychelles warbler we investigate individual variation in the onset and rate of senescence and on age-dependent fitness performance. We are particularly interested in the physiological, ecological and social factors that influence the patterns of senescence. Important physiological mechanisms that influence senescence include oxidative stress and telomere attrition. Oxidative stress affects the rate at which the protective telomere chromosome caps are lost. Telomere lengths are important in determining cellular lifespans and may play a key role in determining organismal lifespans. We investigate senescence at two levels. First, we investigate how social behaviour, reproductive effort, environmental conditions and diseases influence oxidative stress and telomere dynamics. Second, we investigate how these parameters interact and shape patterns of senescence in the wild.
Hormones play an important role in shaping reproductive and life-history traits and may cause differences in behaviour between the sexes. The steroid hormone testosterone is essential for the expression of male reproduction, for example because it influences mating success. However, the functional role of testosterone in females is still poorly understood. Using a wild blue tit population, we experimentally investigate the role of testosterone in shaping female reproductive behaviour.
- Telomeres as biomarkers of costs and quality in a wild population
- Individual model based analysis of the causes of senescence
- Physiological consequences of different life-history strategies
- Influence of testosterone on female life history traits
Barrett E.L.B., Burke T., Hammers M., Komdeur J. & Richardson D.S. (2013): Telomere dynamics predict mortality in the wild. Mol. Ecol., in press.
De Jong B., Komdeur J., Vedder O., Lens L., & Groothuis T. (2013) No evidence for sexually antagonistic selection on testosterone levels: an experiment in free-living female blue tits (Cyanistes caeruleus). Under review.
Hammers M., Richardson D.S., Burke T. & Komdeur J. (2012): Age-dependent terminal declines in reproductive output in a wild bird. PLoS ONE 7, E209.
Van de Crommenacker J., Richardson D.S., Koltz A.M., Hutchings K. & Komdeur J. (2012): Parasitic infection and oxidative stress are associated and vary with breeding activity in the Seychelles warbler. Proc. R. Soc. Lond. B. 279, 1466-1476.
Eikenaar C., Whitham M., Komdeur J., Van der Velde M. & Moore I.T. (2011): Testosterone, plumage colouration and extra-pair paternity in male North-American barn swallows. PloS ONE 6, e23288.
Van de Crommenacker J., Komdeur J., Burke T. & Richardson D.S. (2011): Spatio-temporal variation in territory quality and oxidative status: a natural experiment in the Seychelles warbler (Acrocephalus sechellensis). J. Anim. Ecol. 80, 668-680.
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