Environmental parental effects, also known as transgenerational plasticity, are widespread in plants and animals. Less well known is whether those effects contribute to maternal fitness in the same manner in different populations. We carried out a multi-generational laboratory experiment with females drawn from two populations of the Least Killifish, Heterandria formosa, to assess transgenerational plasticity in reproductive traits in response to differences in social density and its effects on maternal fitness. In the first and second generations, increased density decreased reproductive rate and increased offspring size in females from both populations. There were complicated patterns of transgenerational plasticity on maternal fitness that differed between females from different populations. Females from a population with historically low densities whose mothers experienced lower density had higher fitness than females whose mothers experienced higher density, regardless of their own density. The opposite pattern emerged in females from the population with historically high densities: females whose mothers experienced higher density had higher fitness than females whose mothers experienced lower density. This transgenerational plasticity is not anticipatory but might be considered adaptive in both populations if providing those “silver spoons” enhances offspring fitness in all environments.

This dataset was generated for an experiment involving the least killifish, Heterandria formosa. We carried out a multi-generational laboratory experiment with females drawn from two populations of H. formosa to assess transgenerational plasticity in reproductive traits in response to differences in social density and its effects on maternal fitness. Fish were housed in high or low social density tanks, and each tank's reproductive output in terms of offspring mass and number was recorded daily for six weeks. These data contain each tank in each generation, offspring mass, and number across each week.

The data are available in Excel and could be imported into any number of statistical analysis programs.