Life-history traits of soil collembolans in relation to food quality

Preference studies of many different collembolan species have categorised collembolans being selective in their food choice. To clarify whether collembolan food selectivity is related to fitness parameters, three species, Folsomia fimetaria, Protaphorura armata and Heteromurus nitidus, were fed three fungal species, Alternaria infectoria, Mucor hiemalis and Penicillium hordei, representing fungi of high, medium and low preference. The fungal diets were grown on soil and collembolan growth, survival and fecundity were measured. The fungus A. infectoria supported growth, survival and reproduction best in all three species of collembolans, while the fungus P. hordei was of low food quality. M. hiemalis was of medium quality and F. fimetaria was the only collembolan reproducing on M. hiemalis. F. fimetaria favoured reproduction over growth when confined to M. hiemalis. When P. armata was fed M. hiemalis it reached a size where reproduction normally starts, but no young were produced. This suggests that M. hiemalis lacks nutrients necessary for reproduction. H. nitidus did not perform well on any of the fungi offered, which were generally of low food quality for this species. In this study, where the fungal growth substrate is soil, there is a clear relationship between collembolan fitness and their food choice in contrast to some other studies where substrates optimised for fungal growth had been used. We show that specific fungal species are important for resource allocation to growth or reproduction and closely connected with food choice. Further, we argue that natural fungal growth substrates, such as soil, should be used in experiments of this kind.