Intraspecific competition can drive selection favouring use of novel resources. However, the genetic variation for resource use on which this evolutionary step depends could also cause weaker competition. In a recent study
(Agashe and Bolnick) tested the possible alternative effects on niche expansion. They factorially manipulated both the degree of genetic variation and population density in flour beetles (Tribolium castaneum) exposed to both novel and familiar food resources. Using stable carbon isotope analysis, they measured temporal change and individual variation in beetle diet across eight generations. Intraspecific competition and genetic variation acted on different components of niche evolution: competition facilitated niche expansion, while genetic variation increased individual variation in niche use. In addition, genetic variation and competition together facilitated niche expansion, but all these impacts were temporally variable. Thus, they show that the interaction between genetic variation and competition can also determine niche evolution at different time scales.
(Source: Proceedings of The Royal Society Biological sciences, 12.05.2010)