  A Markovian model of group-structured (two-level) population dynamics
features births, deaths, and migrations of individuals, and fission and
extinction of groups. These models are useful for studying group selection and
other evolutionary processes that occur when individuals live in distinct
groups. We show that the sample paths of a properly scaled sequence of these
models converge in an appropriate Skorohod space to a deterministic trajectory
that is a unique solution to a quasilinear evolution equation. The PDE model
can therefore be justified as an approximation to the Markovian one.
