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The effects of reproduction on senescence in breeding birds

Spaans, Manon (2018) The effects of reproduction on senescence in breeding birds. Bachelor's Thesis, Biology.


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Declining survival and reproduction are part of life history. The decline of fitness components with age is called senescence and can be measured as actuarial senescence and as reproductive senescence. Due to high extrinsic mortality senescence was thought not to happen in wild populations, although lately many studies have shown that senescence does occur in wild populations. The disposable soma theory and antagonistic pleiotropy theory both predict trade-offs between current reproductive investment, and survival and reproduction later in life. Experimental studies have showed that increased reproductive effort leads to accelerated senescence. In this thesis I will compare the relationship between and within longer and shorter living bird species. Longer and shorter living birds adopt very different reproductive strategies. Shorter living birds invest more in early life reproduction while longer living birds invest less in reproduction and more in somatic maintenance. Senescence due to reproduction eventually does occur in longer living species but at a much older age because of their low reproductive investment and high investment in maintenance. Within species these differences also arise, with some individuals investing more in reproduction also senesce faster, although some studies also found that high quality individuals do not seem to face costs of reproduction in terms of accelerated senescence. I also compare the impact of reproduction on senescence between males and females. In mammals male biased mortality is very general, however, male biased senescence is not as obvious in birds because of lower male-male competition, increased female biased senescence due to parental care and because the female is the heterogametic sex which is associated with higher mortality due to deleterious mutations on the sex chromosomes. Finally, I will explain how it may be possible that birds generally live longer than mammals in terms of protection against oxidative stress and I will discuss if the effects of reproduction on oxidative stress can be measured via telomere shortening. Overall, these findings support the disposable soma theory which states that higher investment in reproduction leads to accelerated senescence, however, the antagonistic pleiotropy theory cannot be excluded which emphasizes the need for more genetic based research.

Item Type: Thesis (Bachelor's Thesis)
Supervisor name: Hammers, M.
Degree programme: Biology
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 19 Apr 2018
Last Modified: 02 May 2018 11:22

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