A shadow system appears as a limit of a reaction-diffusion
system in
which some components have infinite diffusivity.
We investigate the
spatial structure of its stable solutions. It is
known that, unlike
scalar reaction-diffusion equations, some shadow
systems may have
stable nonconstant (monotone) solutions. On the
other hand, it is
also known that in autonomous shadow
systems any nonconstant
non-monotone stationary solution is necessarily
unstable. In this
paper, it is shown in a general setting that any stable
bounded (not
necessarily stationary) solution is asymptotically
homogeneous or
eventually monotone in $x$.