Biology Reference
In-Depth Information
Given this mathematical equivalence, does this mean that the group selection approach is
as equally useful as the inclusive fitness approach? No, because the group selection approach
does not lead to an equivalent maximizing principle. Again, it is necessary to return to
Darwin's distinction between the process (dynamics) and resultant product (design) of
natural selection. Either inclusive fitness or group selection could be used to predict the
dynamics of natural selection and each might be more useful for modelling certain situations.
But, if we are interested in how organisms are designed to behave (adaptation), in terms of
what they will appear to be maximizing, then the answer is that they will appear to be
maximizing their inclusive fitness, and not group fitness. The empirical success of behavioural
ecology is based on this idea of being able to treat organisms as if they are fitness maximizers,
which flows from inclusive fitness theory. In contrast, individuals would only be selected to
maximize group fitness in the extreme scenario where there is no conflict between individuals
within groups, and so within group selection is negligible - and, of course, they are still
selected to maximise their inclusive fitness in that scenario (Gardner & Grafen, 2009).
In addition, the group selection approach is usually less easy to implement, and often
spreads confusion (West et al ., 2007a).
… but does not
lead to a
maximizing
principle
The limitations of
the new group
selection
approach …
… less easy to
develop models
(1) From a theoretical perspective, individual level models are usually both easier to
construct and extend to different biological scenarios. Consequently, while it is possible
to develop an abstract group selection model for a trait like altruism or the sex ratio, it
is much harder to develop models that can be applied and tested with specific species.
(2) It is usually easier to link the individual approach with empirical data, because it
emphasizes easily understood and measured parameters, such as B, C and r .
(3) Possibly because it lacks a direct link between selection and maximization, the group
selection approach often leads to misconceptions. For example, incorrect suggestions
that kin selection is a subset of group selection, or that group selection can apply in
situations where inclusive fitness cannot.
(4) The group selection literature has also led to a strange use of terms such as
altruism. The group selection literature redefines a behaviour as altruistic if it has a
relative fitness disadvantage within the group, irrespective of the between group
component. Because the latter can outweigh the former, such as when by-product
benefits of helping flow to everyone within the group (Chapter 12), this means that
a behaviour would be defined as altruistic even if it increased the direct reproductive
success of the supposed 'altruist' (Table 15.1)!
(5) The group selection approach often leads to the question: at what level does selection
occur? This is usually not very useful or informative because selection can occur at
multiple levels, with the relative importance of different levels (e.g. within or between
group) depending upon the details of the system being modelled (and hence the details
of a particular model and the parameter values of the model). In contrast, if we ask 'at
what level does adaptation occur?', then we can give the very general answer, that it
occurs at the level of the individual, in order to maximize inclusive fitness (Gardner &
Grafen, 2009).
… less easy to link
with empirical
data …
… leads to
misconceptions …
… results in
confusing use of
terms …
… and moves the
focus from
adaptation
To sum up, although the inclusive fitness (or individual) and new group selection
approaches can both be used to give predictions, the inclusive fitness approach has proved
much more useful. All of the advances in our understanding of behaviour that have
Search WWH ::




Custom Search