Data from: Experimental evidence for an eco-evolutionary coupling between local adaptation and intraspecific competition

Determining how adaptive evolution can be coupled to ecological processes is key for developing a more integrative understanding of the demographic factors that regulate populations. Intraspecific competition is an especially important ecological process because it generates negative density-dependence in demographic rates. Although ecological factors are most often investigated to determine the strength of density-dependence, evolutionary processes such as local adaptation could also feedback to shape variation in the strength of density-dependence among populations. Using an experimental approach with damselflies, a predaceous aquatic insect, we find evidence that both density-dependent intraspecific competition and local adaptation affect per capita growth rates. In some cases, the effects of local adaptation on growth rates exceeded the ecological competitive effects of a doubling of density. However, we also found that these ecological and evolutionary properties of populations are coupled, and we offer two interpretations of the causes underlying this pattern: (1) the strength of density-dependent competition depends on the extent of local adaptation, or (2) the extent of local adaptation is shaped by the strength of density-dependent competition. Regardless of the underlying causal pathway, these results show how eco-evolutionary dynamics can affect a key demographic process regulating populations.