Positive Stationary Solutions and Spreading Speeds of KPP Equations in   Locally Spatially Inhomogeneous Media
  The current paper is concerned with positive stationary solutions and spatial spreading speeds of KPP type evolution equations with random or nonlocal or discrete dispersal in locally spatially inhomogeneous media. It is shown that such an equation has a unique globally stable positive stationary solution and has a spreading speed in every direction. Moreover, it is shown that the localized spatial inhomogeneity of the medium neither slows down nor speeds up the spatial spreading in all the directions. 
Liang Kong and Wenxian Shen
math.DS math.AP