  A superprocess limit for an interacting birth-death particle system modelling
a population with trait and physical age-structures is established. Traits of
newborn offspring are inherited from the parents except when mutations occur,
while ages are set to zero. Because of interactions between individuals,
standard approaches based on the Laplace transform do not hold. We use a
martingale problem approach and a separation of the slow (trait) and fast (age)
scales. While the trait marginals converge in a pathwise sense to a
superprocess, the age distributions, on another time scale, average to
equilibria that depend on traits. The convergence of the whole process
depending on trait and age, only holds for finite-dimensional time-marginals.
We apply our results to the study of examples illustrating different cases of
trade-off between competition and senescence.
