The effect of condition-dependent survival on the relative fitness contributions in the initial and second sexes.

<p>a. High- and low-condition individuals have higher and lower survival rates than an average individual (bold). In this example, high-condition individuals exhibit a 10% likelihood of reaching age 1, while those of low-condition exhibit only a 2.5% chance of reaching the second sex. b. For high-condition individuals, the fitness contribution (i.e., the area under the curve) from expected reproduction in the high-payoff second sex is much greater than the expected contribution in the initial sex; the opposite is true for individuals of low-condition. This is an application of Trivers and Willard's <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109626#pone.0109626-Trivers1" target="_blank">[11]</a> modification of Fisher's <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109626#pone.0109626-Fisher1" target="_blank">[7]</a> model of sex ratio evolution to a sequential hermaphrodite.