  Coherence evolution of two food web models can be obtained under the stirring
effect of chaotic advection. Each food web model sustains a three--level
trophic system composed of interacting predators, consumers and vegetation.
These populations compete for a common limiting resource in open flows with
chaotic advection dynamics. Here we show that two species (the top--predators)
of different colonies chaotically advected by a jet--like flow can synchronize
their evolution even without migration interaction. The evolution is
charaterized as a phase synchronization. The phase differences (determined
through the Hilbert transform) of the variables representing those species show
a coherent evolution.
