General Models:                               Specific Models:                              Examples in text:

 

Directed

Reciprocation

X undertakes a significant cost to benefit Y, and Y in turn reciprocates that benefit back to X.

 

Operates within or between species.

 

(Trivers 1971)

 

Partner Fidelity Feedback:

X and Y are associated for an extended series of exchanges that last long enough that a feedback operates: the effect of benefits transferred from X to Y returns and enhances the fitness of X. Thus, by failing to cooperate, individual X ultimately curtails its own fitness.

 

(Bull and Rice 1991, Nowak and May 1992, Frank 1994, Doebeli and Knowlton 1998, Simms and Taylor 2002 )

-Vertically transmitted symbionts, optimal virulence evolution, ant-acacia mutualism.

Partner Choice:

Either individual X1 or X2 receives a benefit from Y, depending on YÕs choice. Y chooses to interact with the X individual that offers greater fitness returns.

 

(Darwin 1859, Eshel and Cavali-Sforza 1982, No‘ 1990, Bull and Rice 1991, Peck 1993, No‘ and Hammerstein 1994, Batali and Kitcher 1995, Frank 1995, in press, Wilson and Dugatkin 1997, West et al 2002b)

-Squid-light organ symbiosis, legume-rhizobium symbiosis, yucca-yucca moth symbiosis, image-scoring in reef fish, allogrooming in impala.

 

 

Shared Genes

 

X benefits X1 with which X shares alleles through descent from a common ancestor.

 

Operates within species only.

 

(Hamilton 1964a,b)

Kin Choice:

X recognizes and directs benefits to more closely related X1 as opposed to more distantly related X2 based on phenotype(s) of X1, X2.

 

(Hamilton 1964a, Eshel and Cavalli-Sforza 1982, Reeve 1989, Queller 2000)

-Exclusion of non-relatives in tunicates, GP9 locus in fire-ants, M-factors in beetles, cell adhesion genes in social amoebae.

Kin Fidelity:

X directs benefits to X1 base upon X1Õs context dependent spatial association with X. This proximity denotes shared genes with X.

 

 

 

 

(Hamilton 1964a, Eshel and Cavalli-Sforza 1982, Reeve 1989, West 2002a)

-Parental care in birds, coinfection in clonal microbes, aposemat-ism in familial groups of aphids.

 

 

Byproducts

 

X benefits Y as a byproduct of an otherwise selfish act of X.

 

Operates within or between species.

 

(West-Eberhard 1975, Brown 1983)

One Way:

An act of X benefits Y as an automatic consequence (byproduct) of XÕs self interested action.

 

(West-Eberhard 1975, Brown 1983,  Connor 1995a)

-Vultures and lions, carrion feeders.

 

Two Way:

Both X and Y each benefit the other as automatic consequences (byproducts) of their own selfish actions. Includes synergism: actions or coordinated behavior that are automatically more fitness-enhancing when performed in groups.

 

 (Hamilton 1971, Queller 1985, Connor 1995a)

-Predator dilution in bugs, selfish herds, Mullerian mimicry, unrelated helpers at the nest, ant colonies founded my multiple queens.

Byproducts Reciprocity:

Y evolves to enhance its benefit to X, which in turn increases the byproducts it receives from X. The byproduct from X does not evolve, but the effect of Y on X does.

                                                                          (Connor 1986)

-Honeyguide-man mutualism.