P. Haccou et Jm. Mcnamara, EFFECTS OF PARENTAL SURVIVAL ON CLUTCH SIZE DECISIONS IN FLUCTUATING ENVIRONMENTS, Evolutionary ecology, 12(4), 1998, pp. 459-475
Whereas in constant environments parental survival has no effect on op
timal clutch size in the absence of trade-offs between juvenile and pa
rental survival, the situation is drastically different in fluctuating
environments. We consider a model in which, with respect to reproduct
ion, parents and offspring are equivalent at the start of the next bre
eding season. When generations are non-overlapping, the clutch size ma
ximizing geometric mean surviving number of offspring is optimal among
all pure clutch size strategies. We prove that, as parental survival
increases relative to that of the offspring, the optimal clutch size c
onverges to the arithmetic mean maximizing clutch size (the so-called
`Lack clutch size'). We also give a numerical procedure for calculatin
g optimal mixed strategies and we show that, as environmental variance
increases and/or parental survival decreases, mixed rather than pure
strategies become optimal. Furthermore, we explain how to estimate fit
ness from empirical data under the assumptions of our model.