The demographic consequences of adaptation:Evidence from experimental evolution

The process of adaptation toward novel environments is directly connected to the acquisition of higher fitness relative to others. Such increased fitness is obtained by changes in life history traits that may directly impact population dynamics. From a functional perspective, increased fitness can be achieved through higher resource use or more efficient resource use, each potentially having its own impact on population dynamics. In the first case, adaptation is expected to directly translate into higher population growth. In the second case, adaptation requires less energy and hence may lead to higher carrying capacity. Adaptation may thus lead to changes in ecological dynamics and vice versa. Here, by using a combination of evolutionary experiments with spider mites and a population dynamic model, we investigate how an increase in fecundity (a validated proxy for adaptation) affects a population’s ecological dynamics. Our results show that adaptation can positively affect population growth rate and either positively or negatively affect carrying capacity, depending on the ecological condition leading to variation in adaptation. These findings show the importance of evolution for population dynamics in changing environments, which may ultimately affect the stability and resilience of populations.