Fig. 1

Natural selection may act on C. elegans fitness at the individual and the colony levels. a Left: the C. elegans individual life cycle. Under favorable conditions, the life cycle takes approximately 3 days. Hatching larvae develop into adults via four larval stages. Under adverse environmental conditions, C. elegans can developmentally arrest as a stress resistant alternative L3 stage, the dauer larva. Right: the C. elegans colony life cycle. Dauer larvae encountering a new food patch establish a new colony, for which production of dauer propagules is a measure of colony fitness (right), just as egg production by individual nematodes is a measure of individual fitness. b Colony fitness is optimized by maximizing efficiency of food conversion into dauers. According to this hypothetical scheme, post-reproductive mothers undergo programmed death to minimize futile food consumption, i.e., that which does not contribute to colony fitness but only to individual fitness. A short reproductive period may contribute to optimization of population structure to reduce numbers of larvae at a stage too early or late to form dauers. Image adapted from an earlier computer modelling study [18]