RESUMO
Understanding the evolution of cooperation is a major question in Evolutionary Biology. Here, we extend a previously proposed mathematical model in Evolutionary Game Theory that investigated how resource use by a single species composed of cooperators and defectors may lead to its maintenance or extinction. We include another species in the model, so as to investigate how different intra and interspecific interactions of cooperative or competitive nature among individuals that share the same essential resource may drive the survival and evolution of the species. Several outcomes emerge from the model, depending on the configuration of the payoff matrix, the individual contribution to the resource pool, the competition intensity between species, and the initial conditions of the system dynamics. Observed results include scenarios in which species thrive due to the action of cooperators, but also scenarios in which both species collapse due to lack of cooperation and, consequently, of resources. In particular, a high initial availability of resources may be the determinant factor to the survival of both species. Interestingly, cooperation may be more favored when individuals have less incentive to cooperate with others, and the survival of their populations may depend crucially on their competitive capacities.
Assuntos
Evolução Biológica , Comportamento Cooperativo , Humanos , Modelos Teóricos , Densidade Demográfica , Teoria dos JogosRESUMO
Mutation and drift play opposite roles in genetics. While mutation creates diversity, drift can cause gene variants to disappear, especially when they are rare. In the absence of natural selection and migration, the balance between the drift and mutation in a well-mixed population defines its diversity. The Moran model captures the effects of these two evolutionary forces and has a counterpart in social dynamics, known as the voter model with external opinion influencers. Two extreme outcomes of the voter model dynamics are consensus and coexistence of opinions, which correspond to low and high diversity in the Moran model. Here we use a Shannon's information-theoretic approach to characterize the smooth transition between the states of consensus and coexistence of opinions in the voter model. Mapping the Moran into the voter model, we extend the results to the mutation-drift balance and characterize the transition between low and high diversity in finite populations. Describing the population as a network of connected individuals, we show that the transition between the two regimes depends on the network topology of the population and on the possible asymmetries in the mutation rates.
RESUMO
Ring species are groups of organisms that dispersed along a ring-shaped region in such a way that the two ends of the population that meet after many generations are reproductively isolated. They provide a rare opportunity to understand the role of spatial structuring in speciation. Here, we simulate the evolution of ring species assuming that individuals become sexually isolated if the genetic distance between them is above a certain threshold. The model incorporates two forms of dispersal limitation: exogenous geographic barriers that limit the population range and endogenous barriers that result in genetic structuring within the population range. As expected, species' properties that reduce gene flow within the population range facilitate the evolution of reproductive isolation and ring species formation. However, if populations are confined to narrow ranges by geographic barriers, ring species formation increases when local mating is less spatially restricted. Ring species are most likely to form if a population expands while confined to a quasi-unidimensional range but preserving high mobility in the direction of the range expansion. These conditions are unlikely to be met or persist in real populations and may explain why ring species are rare.