Data on population dynamics (two-spotted spider mite, Tetranychus urticae) on (tomato) islands and data on female fecundity during an evolutionary experiment. The experiment consisted of tomato islands of three different sizes: Small : 1 tomato plant Medium: 2 tomato plants Large: 4 tomato plants Islands received immigrants (adult females) from the original population (stock population) which was maintained on bean plants. We used three levels of dispersal (number of immigrants): 0.5 mites/week 1 mite/week 2 mites/week Information about the methodology and a detailed description of the study can be found in the associated paper.