For species that rely on ephemeral resources, genotype fitness will depend on traits that affect both population growth rates and dispersal. Understanding how such traits are related is central to understanding how they may evolve. Natural populations of Caenorhabditis elegans exhibit rapid population growth within resource-rich patches of decaying organic material and subsequent dispersal, primarily as developmentally-arrested dauer larvae, between patches. The properties of growing populations of C. elegans are, however, poorly understood. Here we show that food availability, dauer pheromone (a measure of conspecific population density) and temperature affect dauer larvae development in growing populations as would be predicted from analyses of single cohorts of worms. We also show that as food patch size increases, dauer larvae are formed prior to patch exhaustion and that the number of dauer larvae present increases after the patch is exhausted, i.e., worms that had not completed development as dauer larvae when the food was exhausted continue development in the absence of bacterial food. Crucially, the subsequent reproductive fitness of dauer larvae that complete development after the exhaustion of the bacterial food patch is reduced in comparison with dauer larvae that develop prior to patch exhaustion. These results demonstrate that population level analyses of C. elegans are feasible, support previous studies of the environmental factors affecting dauer larvae development and suggest an adaptive benefit for variation between isolates in the sensitivity of dauer larvae development. |
