Food quality influences density-dependent fitness, but not always density-dependent habitat selection, in red flour beetles (Coleoptera: Tenebrionidae)

Density-dependent habitat selection models inherently rely on the negative relationship between population density and mean fitness in different habitats. Habitats differing in quality, such as different food sources or habitat structure, can have different strengths of density-dependent relationships, which can then affect patterns of density dependence in habitat selection. We tested the hypothesis that density dependence in fitness dictates the patterns in density-dependent habitat selection: individuals should prefer higher-quality habitat over lower-quality habitat. We used controlled experiments with red flour beetles (Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)) to measure density dependence of fitness and to examine density-dependent habitat selection by beetles in wheat (Triticum Linnaeus (Poaceae)), corn (Zea mays Linnaeus (Poaceae)), and soy (Glycine max (Linnaeus) Merrill (Fabaceae)) flour habitats. Despite large differences in fitness between habitats (fitness was the highest in wheat flour, lower in corn flour, and zero in soy flour), beetles showed only weak preference for wheat over corn flour and for corn over soy flour, but showed strong preference for wheat over soy flour. These preferences were the strongest at low density. This study gives insight into the relationship between habitat quality and density-dependent habitat selection in flour beetles.