Data from: Inbreeding depression across a nutritional stress continuum

Many natural populations suffer from inbreeding and genetic drift as a consequence of non-random mating or low population sizes. Furthermore they face environmental challenges, which may interact synergistically with deleterious consequences of increased homozygosity and further decrease fitness. Most studies on inbreeding environment (I-E) interactions use one or two stress levels, whereby the resolution of the possible stress and inbreeding depression interaction is low. Here we produced Drosophila melanogaster replicate populations, maintained at three different population sizes (10, 50 and a control size of 500) for 25 generations. A nutritional stress gradient was imposed on the replicate populations by exposing them to 11 different concentrations of yeast in the developmental medium. We assessed the consequences of nutritional stress by scoring egg-to adult viability and body mass of emerged flies. We found 1) unequivocal evidence for I-E interactions in egg-to-adult viability and to a lesser extent in dry body mass with inbreeding depression being more severe under nutritional stress, 2) the rate of increase in inbreeding depression with increased nutritional stress was higher for replicate populations of size 10 than for populations of size 50, 3) the rate of increase in inbreeding depression decreased at higher stress levels, and 4) increasing nutritional stress levels resulted in a faster increase in number of lethal equivalents in replicate populations of size 10 compared to populations of size 50. Our data provide novel and strong evidence that deleterious fitness consequences of I-E interactions are more pronounced at higher nutritional stress and at higher inbreeding levels.