Female preference for net with many egg: A cost-benefit analysis of female choice in fish with paternal care

Abstract

In several fish species with paternal care, females prefer males guarding eggs in their nest. This preference might be advantageous because the presence of many other eggs dilutes the risk of newly eggs being eaten by the father. To evaluate this hypothesis quantitatively, we constructed a simulation model that mimics the breeding biology of the blenny Aidablennius sphynx. In contrast to earlier verbal models, the costs of choice are explicitly taken into account. We systematically varied factors such as the stringency of choosiness and the level and nature of the costs of choice. For realistic parameter values female choosiness may result in a fitness advantage of more than 50%. The optimal choice strategy created a distribution of eggs move the nests which resemble that found in the field for A. sphynx. Our model shows that the relative fitness of a choice strategy is not constant but frequency dependent way. If most females are choosy, a bimodal distribution of egg profitable, since randomly laying female will often lay their eggs in nets with few eggs, producing high mortality per egg due to filial cannibalism. If on the layer hand, only few chooser are present, their influence on the egg distribution is limited. A unimodal distribution result which is profitable for nonchoosers, since the average egg mortality is low and nonchoosers do not bear the costs of choice. The positive relation between chooser frequency and chooser fitness make it easy to understand why choosiness is evolutionary table. However it is not obvious how the trait is established by selection in the first place.