Abstracts (first author)
Modeling the relationship between age specific fecundity and lifespan in a cohort of fruit flies
Populations of laboratory animals that are selected for increased lifespan often show correlated negative responses in early fecundity. However in some cases late fecundity, or total lifetime fecundity, is higher in the populations selected for increase lifespan. By some, this has been interpreted as a falsification of the disposable soma theory. According to the Y–model, in which the effects of variation in allocation and acquisition on life histories are studied, an alternative is suggested. A negative relationship between lifespan and reproduction can be viewed as variation in allocation, whereas a positive relationship is the result of variation in acquisition. We have analyzed age specific fecundity and lifespan in a cohort of Drosophila melanogaster flies which were individually housed. Early fecundity related negatively with lifespan, while late fecundity related positively with lifespan in the same cohort. We show that a model which incorporates the ideas of the Y-model, disposable soma theory and a decrease in physiological performance when age increases, can explain how the relationship between fecundity and lifespan changes with age. Furthermore, we modeled different environments in which there is variation in extrinsic mortality rates. In high mortality environments there was selection for high early fecundity, low late fecundity and low lifespans, whereas the opposite was true for low mortality environments. Our laboratory population of D. melanogaster was founded from a combination of flies from different areas in Europe and therefore is heterogeneous in genotype. We conclude that the differences in life history strategies found in one cohort of laboratory flies are the result of a mosaic of selection on the relationship between fecundity and lifespan over age.