  We consider the Fisher-KPP equation on a three-dimensional domain surrounded
by a thin layer whose diffusion rates are drastically different from that in
the bulk. The bulk is isotropic, while the layer is considered to be
anisotropic and ``optimally aligned", where the normal direction is always an
eigenvector of the diffusion tensor. To see the effect of the layer, we derive
effective boundary conditions (EBCs) by the limiting solution of the Fisher-KPP
equation as the thickness of the layer shrinks to zero. These EBCs contain some
exotic boundary conditions including the Dirichlet-to-Neumann mapping and the
Fractional Laplacian. Moreover, we emphasize that each EBC keeps effective
indefinitely, even as time approaches infinity.
