Population density affects beetle fitness

In any given population of organisms, population numbers are intrinsically controlled by facilitation and competition between individuals for a limited pool of resources in the environment. Facilitation, sometimes referred to as positive density dependent fitness, promotes population growth by rewarding organisms that cooperate with increased survival and fecundity. Competition, also known as negative density dependent fitness, can lead to a decrease in population growth when resources necessary to sustain the population are in short supply. In this study, I tested to see if there are opposite density dependent effects on fitness between the adult and larval life stages of Chrysochus cobaltinus. This was tested by measuring the fecundity of adult beetles on plants with differing population densities in the wild and in a greenhouse. In the larval stage, the survival rate of differing densities of beetles on a single plant was measured to determine fitness. Thus far, I found that the greenhouse reared adult beetles exhibit negative density dependence, while the wild adult and larval populations have not yielded statistically significant data due unexpectedly small sample sizes. This study demonstrates negative density dependence in the adult stage of a novel system with great potential for further experimentation.