Steady states of a selection-mutation model for an age structured population

We introduce a selection-mutation model for an age and age at maturity structured population. The age at maturity is considered an evolutionary trait on which the vital rates depend, subject to selection by competition, and to mutation modelled by a birth term which takes the form of a convolution-like operator. We prove well-posedness of the initial value problem and the existence of non-trivial steady states under suitable hypotheses which yield uniqueness when the interaction variable is one-dimensional.