AbstractsBiology & Animal Science

Senescence is characterized by age-related deterioration within individual organisms and a resultant decline in rates of survival or reproduction. Such declines seem inherently maladaptive, but occur nonetheless in a wide range of species. My thesis contributes to the questions of (i) why senescence is common in nature, and (ii) why patterns of senescence sometimes vary markedly both within and among species. With respect to why senescence is common, most evolutionary theory on senescence makes the simplifying assumption that all offspring are of equal quality. I show that this assumption does not hold in the aquatic plant Lemna minor, and develop a theoretical model to investigate how age-related declines in offspring quality influence the ‘force’ of natural selection. With respect to variation in patterns of senescence, I describe a common garden experiment demonstrating a high degree of among-population consistency in life expectancy and rates of senescence in L. minor.