Maternal effects on offspring size in a natural population of the viviparous tsetse fly : Maternal effects in tsetse flies

The assumption of costs of reproduction were a logical necessity for much of the early development of life history theory. An unfortunate property of 'logical necessities' is that it is easy to also assume that they must be true. What if this does not turn out to be the case? The existence and universality of costs of reproduction were initially challenged with empirical data of questionable value, but later with increasingly strong theoretical and empirical results. Here, we discuss Ken Spitze's 'superfleas', which represent what we consider to be the strongest empirical challenge to the universality of costs, then offer a possible explanation for their existence.

Life-history theory is concerned with strategic decisions over an organism's lifetime. Evidence is accumulating about the way in which these decisions depend on the organism's physiological state and other components such as external circumstances. Phenotypic plasticity may be interpreted as an organism's response to its state. The quality of offspring may depend on the state and behaviour of the mother. Recent theoretical advances allow these and other state-dependent effects to be modelled within the same framework.