  This paper studies invasion waves in the diffusive
Competitor-Competitor-Mutualist model generalizing the 2-species Lotka-Volterra
model studied by Weinberger et al. The mutualist may benefit the invading or
the resident species producing two different types of invasions. Sufficient
conditions for linear determinacy are derived in both cases, and when they
hold, explicit formulas for linear spreading speeds of the invasions are
obtained by linearizing the model. While in the first case the linear speed is
increased by the mutualist, it is unaffected in the second case. Mathematical
methods are based on converting the model into a cooperative reaction-diffusion
system.
