Ma. Rodriguezgirones et al., THE EVOLUTION OF BEGGING - SIGNALING AND SIBLING COMPETITION, Proceedings of the National Academy of Sciences of the United Statesof America, 93(25), 1996, pp. 14637-14641
In many species, young solicit food from their parents, which respond
by feeding them, Because of the difference in genetic make-up between
parents and their offspring and the consequent conflict, this interact
ion is often studied as a paradigm for the evolution of communication,
Existent theoretical models demonstrate that chick signaling and pare
nt responding can be stable if solicitation is a costly signal, The ma
rginal cost of producing stronger signals allows the system to converg
e to an equilibrium: young beg with intensity that reflects their need
, and parents use this information to maximize their own inclusive fit
ness, However, we show that there is another equilibrium where chicks
do not beg and parents' provisioning effort is optimal with respect to
the statistically probable distribution of chicks' states, Expected f
itness for parents and offspring at the nonsignaling equilibrium is hi
gher than at the signaling equilibrium, Because nonsignaling is stable
and it is Likely to be the ancestral condition, we would like to know
how natural systems evolved from nonsignaling to signaling, We sugges
t that begging may have evolved through direct sibling fighting before
the establishment of a parental response, that is, that nonsignaling
squabbling leads to signaling. In multiple-offspring broods, young fol
lowing a condition-dependent strategy in the contest for resources pro
vide information about their condition. Parents can use this informati
on even though it is not an adaptation for communication, and evolutio
n will lead the system to the signaling equilibrium, This interpretati
on implies that signaling evolved in multiple-offspring broods, but gi
ven that signaling is evolutionarily stable, it would also be favored
in species which secondarily evolved single-chick broods.