Relative fitnesses of the four phenotypes.

<p>The relative fitness of individuals carrying the <i>T</i> trait can differ from that of individuals carrying the <i>t</i> trait. The amount of this difference is dictated by the <b>N</b> state: the <i>N</i> trait confers a fitness difference of <i>σ</i>₁ between <i>TN</i> and <i>tN</i>, and the <i>n</i> trait confers a fitness difference of <i>σ</i>₂ between <i>Tn</i> and <i>tn</i>.