Current models of biological communication point at evolutionary mecha
nisms of particular signal types. Those that present complete models l
ook at the signals' equilibrium values and their evolutionary stabilit
y, and require two simultaneous equations: an equation that describes
the signaler's fitness as a function of the signal and of the recipien
ts' response, and a simultaneous equation that represents the fitness
of recipients. This paper examines the effect of different signal type
s, such as handicaps, amplifiers, camouflage, mimicry etc, on the firs
t equation. By considering parameters that affect the evolution of sig
nals this paper first constructs a general model of biological signali
ng. Different signal types are then characterized by different sets of
limiting assumptions. As a result, the fitness of a signaler of each
signal type is represented by a unique equation that is a mathematical
derivation of the general signaling model. This analysis enables a na
tural division of signals into groups and subgroups that share similar
assumptions and properties. It shows the importance of signal design,
and points at three methods by which signals may be reliable: by trad
e-offs between cost and benefits, by design and by convention. (C) Aca
demic Press Limited.