Biology Reprints
http://hdl.handle.net/1773/1981
2024-03-28T15:37:34ZSignalling Among Relatives. I. When is signalling too costly?
http://hdl.handle.net/1773/2013
Signalling Among Relatives. I. When is signalling too costly?
Bergstrom, Carl T.; Lachmann, Michael
Zahavi's handicap principle, originally proposed as an explanation for sexual selection of elaborate male traits (Zahavi, 1975) suggests that signalling can be honest if less desirable signallers must pay a higher cost in order to signal. Maynard Smith (1991) and Johnstone and Grafen (1992) introduce the Sir Philip Sidney Game in order to apply the handicap principle to the case of signalling among relatives and demonstrate the potential for stable costly signalling systems among relatives.
In this paper, we determine the factors which dictate signal cost and signal value in a generalized version of the Sir Philip Sidney game. This allows us to demonstrate that in both the discrete and continuous versions of the Sir Philip Sidney game, there exist conditions under which costly signalling among relatives is "too costly" to be worthwhile for either participant. Although with costly signalling the benefits associated with honest information transfer become available, the cost incurred may leave all participants worse off, even when costly signalling is itself stable. This possibility raises concerns about the evolutionary pathways which could have lead to the existence of such equilibria in nature. The paper stresses the importance of comparing signalling equilibria with other possible strategies before drawing conclusions regarding the optimality of signalling.
1997-01-01T00:00:00ZSignalling among relatives. II. Beyond the Tower of Babel.
http://hdl.handle.net/1773/2012
Signalling among relatives. II. Beyond the Tower of Babel.
Bergstrom, Carl T.; Lachmann, Michael
Models of costly signalling are commonly employed in evolutionary biology in order to explain how honest communication between individuals with conflicting interests can be stable. These models have focused primarily on a single type of honest signalling equilibrium, the separating equilibrium in which any two different signallers send distinct signals, thereby providing signal receivers with complete information. In this paper, we demonstrate that in signalling among relatives (modelled using the Sir Philip Sidney game), there are not one but a large number of possible signalling equilibria, most of which are pooling equilibria in which different types of signallers may share a common signal. We prove that in a general Sir Philip Sidney game, any partition of signallers into equi-signalling classes can have a stable signalling equilibrium if and only if it is a contiguous partition, and provide examples of such partitions. A similar (but slightly stricter) condition is shown to hold when signals are transmitted through a medium with signalling error. These results suggest a solution to a problem faced by previous signalling theory models: when we consider the separating equilibrium, signal cost is independent of the frequency of individuals sending that signal and, consequently, even very rare signaller types can drastically affect signal cost. Here, we show that by allowing these rare signallers to pool with more common signallers, signal cost can be greatly reduced.
1998-01-01T00:00:00ZThe Red King Effect: Evolutionary rates and the division of surpluses in mutualisms
http://hdl.handle.net/1773/1996
The Red King Effect: Evolutionary rates and the division of surpluses in mutualisms
Bergstrom, Carl T.; Lachmann, Michael
Mutualisms generate surpluses. While much of the theoretical literature to date focuses on mechanisms by which cooperation is stabilized so that these surpluses can continue to be produced and enjoyed, we address a second question: how will these surpluses be distributed among the participants? We approach this question from an evolutionary game theory perspective, exploring how the coevolutionary process selects an equilibrium division of the surplus from among the many possibilities.
We place particular emphasis on the importance of the relative rates of evolution of the two species. Contrary to the Red Queen hypothesis, which suggests that fast evolution is favored in coevolutionary interactions, we find that slowly evolving species are likely to gain a disproportionate fraction of the surplus generated through mutualism. This occurs because on an evolutionary timescale, slow evolution effectively ties the hands of a species, allowing it to commit to threats and thus bargain more effectively with its partner over the course of the coevolutionary process.
2003-01-01T00:00:00Z