Figure 2

Overview of the hierarchical sampling design followed when collecting the eggs from which the larvae used in the experiment originated. Six species were sampled, of which two occur in Northern Europe (a, b), two occur in Central Europe (c, d) and two occur in Southern Europe (e, f) (referred to as species distributions). From each species, we sampled populations from near the northern and southern range margin, as well as in the central part of each species’ range (gray squares in a–f; referred to as latitudinal populations). From each latitudinal population, we typically sampled three different ponds, streams or lakes (referred to as subpopulations). An example of these subpopulations is shown for C. armatum in g. Genetic variances were estimated at the level of latitudinal populations, combining data from all three subpopulations.