  We study front propagation when an invading species competes with a resident;
we assume nearest-neighbor preemptive competition for resources in an
individual-based, two-dimensional lattice model. The asymptotic front velocity
exhibits power-law dependence on the difference between the two species' clonal
propagation rates (key ecological parameters). The mean-field approximation
behaves similarly, but the power law's exponent slightly differs from the
individual-based model's result. We also study roughening of the front, using
the framework of non-equilibrium interface growth. Our analysis indicates that
initially flat, linear invading fronts exhibit Kardar-Parisi-Zhang (KPZ)
roughening in one transverse dimension. Further, this finding implies, and is
also confirmed by simulations, that the temporal correction to the asymptotic
front velocity is of ${\cal O}(t^{-2/3})$.
