Density‐dependent selection at high food levels leads to the evolution of persistence but not constancy in Drosophila melanogaster populations

Mechanisms through which population dynamics evolve to be stable have been of considerable interest in population biology. One of the ways in which population stability is likely to evolve is via density‐dependent selection with or without an inverse relationship between intrinsic per capita population growth rate ( r ) and equilibrium population size ( K ). Here, we test a previously articulated hypothesis about whether and how the specific combination of egg number and food amount under which density‐dependent selection is implemented affects the evolution of population stability attributes in Drosophila populations subjected to chronic larval crowding in the laboratory. We find that D. melanogaster populations subjected to larval crowding at relatively large amounts of food per vial have evolved higher persistence (lower probability of extinction) stability than controls, although constancy stability (reduced population size fluctuations) did not evolve. Moreover, these populations did not show an inverse relationship between the parameters r and K , and evolved persistence largely through a significant decrease in sensitivity of growth rate to population density, especially at densities ranging from medium to equilibrium population size. Qualitative comparison of these findings with those from another set of crowding‐adapted (but at relatively low food amounts per vial) D. melanogaster populations that had evolved both constancy and persistence stability, suggests that the specific ecology of larval crowding in terms of food amount does indeed influence the consequent evolution of stability attributes, perhaps largely through differences in the pattern of sensitivity of population growth rate to population density.