Three modes of reproduction in all-female species of hybrid origin (a-c) compared to bi-sexual reproduction in true species (d). Boxes represent diploid individuals, circles and ellipses represent eggs and sperm, respectively. Letters in boxes depict genomes of two different species (A and B in Figure 1a–c) or different sexes within a species (A and A* in Figure 1d). Superscripts (' and +) on letters in gametes indicate that, due to recombination, these gametes contain a unique combination of genes, whereas gametes without superscripted letters contain clonal genomes. As a result of the different reproductive modes the offspring are genetically either identical to their mother (AB in Figure 1a, b), highly variable (A'A+ in Figure 1d) or intermediate with one clonal and one recombined genome (AB' in Figure 1c). White = females, grey = males. For further explanations see Introduction.