Cooperation - An Introduction to Behavioural Ecology - page 358

which appeared on the ground were often marked ones, in other words eggs which had
been removed from nests (Feare, 1984). In this case, just as with interspecific brood
parasitism, the host is being tricked into behaving for another individual's benefit.
Summary
We have distinguished four ways in which cooperation can evolve (Table 12.2). The first
(kin selection) relies on cooperation providing indirect benefits towards relatives, and
the other three rely on cooperation providing an overall direct benefit to the cooperator.
(1) Kin selection. An individual can increase its genetic representation in future
generations by helping relatives, who share copies of the cooperative gene. There
are numerous examples of kin selection leading to cooperation, such as cooperative
breeding in the long-tailed tit and the formation of fruiting bodies in slime moulds.
(2) By-product benefits. Cooperation can provide a benefit, as a by-product, or automatic
consequence, of an otherwise 'self-interested' act. Examples include cooperative
nest founding in ants and helping to increase group size in meerkats.
(3) Reciprocity. Reciprocal cooperation can be favoured, if individuals preferentially
direct help towards those that have previously helped them. Although this is a
theoretically appealing idea, and likely to play a role in humans, it is thought to be
generally unimportant in other animals.
(4) Enforcement. If cooperation is rewarded and/or free riding punished, then this can
alter the benefit/cost ratio of helping, and hence favour cooperation. Examples
include eviction in meerkats, punishment of cleaner fish and the sanctioning of
rhizobia by soybeans.
In many species, multiple factors can be at play, making it hard to disentangle their
relative importance. Nonetheless, it is clear that the relative importance of direct and
indirect benefits varies hugely across species.
Further reading
Lehman and Keller (2006) provide a comprehensive review of the evolutionary models
that have been developed to explain cooperation, followed by 15 commentaries discussing
their overview. Sachs et al . (2004) and West et al . (2007b) discuss how different explanations
can be important in different organisms. There are a variety of reviews focusing on
cooperation in specific taxa, including birds (Koenig & Dickinson, 2004; Hatchwell, 2009),
mammals (Clutton-Brock, 2009b), primates (Silk, 2009), fish (Taborsky 1994) and
microbes (West et al ., 2006). Classic early works on birds are Brown (1987) and Emlen and
Wregge (1988, 1989). Rubenstein & Lovette (2007, 2009) show by comparative analyses
that cooperative breeding in African starlings is associated with temporally variable
environments, and that increased female- female competition for reproductive
opportunities in these cooperative breeders has selected for more ornamented females
and hence less sexual dimorphism. Arnold & Owens (1998, 1999) discuss the ecological
and life history correlates of cooperative breeding in birds. The importance of queuing