Trait-based ecology has taken the forefront of species interactions in recent years. Mathematical models of species coexistence has traditionally been built around population dynamics models that assume individuals of a species are identical in regards to intraspecific and interspecific interactions. Recent work has explored incorporating intraspecific variation to study their effects on the coexistence conditions of two species competition from modern coexistence theory. A majority of these models make strong assumptions on how the traits are distributed (e.g. normally distributed) and how much the distribution can change through time. With the realisation that contemporary evolution plays an important role in ecology through eco-evolutionary feedbacks, mathematical models that capture eco-evolutionary feedbacks are required to understand the complex processes at play. I have built eco-evolutionary models of two species competition and antagonism that allow for intraspecific variation to change through time. With these models, I ask how interaction effects due to trait overlap and natural selection affect the coexistence in two species competition and antagonism. I solve the models numerically using a finite difference method and also derive sufficient conditions for coexistence based on ideas from mutual invasibility analysis.
Results/Conclusions
I find that incorporating intraspecific variation that can change through time in two species eco-evolutionary dynamics can either be conducive or restrictive to coexistence in competition and antagonism. For two species competition, coexistence can be achieved through character displacement when optimal trait values of the two species are very close to each other. Coexistence is easier to achieve as the optimal trait values increase, strengths of selection decreases, effect of intraspecific (interspecific) competition due to trait overlap decreases (increases). This can be contrasted with the classical result that intraspecific competition must be stronger than interspecific competition for coexistence. This is still valid here as the effect of competition increases, net competition on a species averaged over the average interaction of all individuals will decrease.
The results are also in concordance with adaptive dynamics models which identify conditions for evolutionary branching. Population genetics and quantitative genetics model which allow for genetic variation to change, show that genetic variation in the exploiter is always much lower than the genetic variation in the victim .This result also holds true for my eco-evolutionary model.