Weak assortative mating and strong habitat coupling promote the evolution of habitat generalists with a high degree of phenotypic plasticity

Background/Question/Methods

Anthropogenic influences repeatedly lower visual conditions in aquatic environments through, for example, eutrophication. There is some evidence that habitat coupling is more pronounced and assortative mating is weakened in lakes with low visibility. Both of these factors, weakened assortative mating and stronger habitat coupling, can cause the populations to become more habitat generalists. In generalist populations, phenotypic plasticity may be favored because it is advantageous to match phenotypes to the resources individuals currently exploit. Here we test our hypothesis that low assortative mating and strong habitat coupling favors the evolution of generalists and a high degree of phenotypic plasticity. We developed a stochastic individual based simulation model of a sexually reproducing predator population whose ecological (foraging) trait and phenotypic plasticity can evolve, and asexual non-evolving prey populations. Predators can exploit two prey types living in two separate habitats, and attack rate and handling time depend on predator’s phenotypes. Mating can occur in a common (“global mating”) or separate mating grounds (“local mating”). The degree of assortative mating is varied by tuning female choosiness for mates and habitat coupling by tuning predator’s sensitivity to differences in habitat quality. We examine how these two parameters affect the degree of plasticity evolved.

Results/Conclusions

We found that generalists with higher phenotypic plasticity evolve when assortative mating is weak in both mating scenarios. When both female choosiness and habitat sensitivity are strong, specialists with low plasticity evolve in the local mating scenario. In the global mating scenario, on the other hand, in addition to the pattern described above generalists with low plasticity also evolve when the strength of female choosiness is intermediate. The results demonstrate that under weak assortative mating habitat generalists with high phenotypic plasticity can evolve. Strong habitat coupling often leads to the evolution of generalists regardless of the degree of female choosiness. When female choosiness is strong and habitat coupling is weak, specialists can arise and evolve low plasticity. Our results suggest that anthropogenic changes in lakes may promote the evolution of habitat generalists with high phenotypic plasticity due to strong habitat coupling and weakened assortative mating.