Biology Reference
In-Depth Information
(a)
(b)
Fig. 13.9
(a) Naked
mole-rat queen
with young and
(b) a Damaraland
mole-rat. Photo
(a) © Neil
Bromhall;
(b) © Andrew
Young.
could favour group living and cooperation, to more efficiently forage for food. Chris
Faulkes and colleagues (1997) tested this hypothesis with a comparative study across 12
species of mole-rat. Across species, they found that, as predicted, larger groups are
associated with a lower density of food and a greater variation in rainfall.
Sociality in
mole-rats is
correlated with
conditions where
it is hard to
obtain food
Conflict within insect societies
In the previous sections of this chapter, we have examined how kin selection theory
provides an explanation for the evolution of the sterile worker caste in the social insects.
However, it also predicts when conflict could occur. The key point here is that when
relatedness is greater than zero there is the potential for cooperation, but as long as it is
also less than 1.0 there is also the potential for conflict, because individuals can be
selected to obtain a disproportionate share of the reproductive success. In the following
sections of this chapter two areas are discussed where conflict arises within colonies of
hymenopteran social insects: the sex ratio and who should produce male eggs. Our
general question will be: 'Given that there are queen and worker castes, how do queens
and workers maximize their genetic contribution to the next generation?'. Put another
way, when do conflicts arise, how are they resolved and who wins? In both of the areas
examined, we will find that kin selection theory makes clear predictions about when
conflict will arise, that the precise form of the conflicts depend upon the asymmetries
that result from haplodiploid genetics, and that there is a remarkable level of empirical
support for these predictions.
Kin selection
theory predicts
both cooperation
and conflict
Conflict over the sex ratio in the
social hymenoptera
Queen-worker conflict
In Chapter 10 we discussed how individuals could be selected to adjust the sex of their
offspring in response to local conditions. Let us now consider selection on sex ratio
within the hymenopteran social insects; firstly, from the point of view of the queen.
