Biology 3466B Lecture Notes - Pollinium, Evolutionarily Stable Strategy, Reciprocal Altruism
25 Aug 2013
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Document Summary
Frequecny-dependent selection occurs when the fitness of individuals with a particular phenotype depends on their frequency in the population. For example, elderflower orchids blossom as purple and yellow morphs and because neither flower type offers a pollinator reward, bumblebees alternate their visits between flowers of each colour in search of a reward. For all estimates of relative reproductive success, the identity of the morph that has the relative advantage reverses as the frequency of yellow plants increases. At both extreme frequencies, the rare morph has a significantly higher value for all indices of reproductive success considered, compared with the common morph. This shows that negative frequency-dependent selection, mediated through pollinator foraging preference, has the potential to maintain a color polymorphism in natural plant populations. Where the fitness of yellow flowers and purple flowers is equal, the evolutionarily stable strategy (ess) states that natural selection will push towards this point (no individual can do better by adopting another strategy).
