Fig. 2

Results of crossings experiments of P. ridibundus individuals and diploid hybrid females with P. ridibundus and diploid P. esculentus males. Tadpoles obtained after crossings were represented by triploid hybrids with RRL and LLR genotypes, P. ridibundus (RR) and P. esculentus (RL) individuals. Diploid hybrid females produced oocytes with 26 bi- and univalents corresponding to P. ridibundus (orange) and P. lessonae (blue) chromosomes, 13 bivalents corresponding to P. ridibundus (orange) chromosomes. Obtained results allow us to assume that diploid hybrid females produce unreduced gametes (RL) and gametes with P. ridibundus (R) or P. lessonae (L) genomes. Oocytes with 26 univalents presumably cannot overcome meiosis and give aneuploidy gametes. Diploid hybrid males presumably produce haploid sperm with P. ridibundus (R) and P. lessonae (L) genomes. Two P. ridibundus individuals produce haploid gametes with P. ridibundus genome. Question marks (?) indicate discrepancy between oocyte chromosomal sets and gametes genome composition inferred from crossing experiments. Crossing numbers correspond to Additional file 1: Table S1