Non‐hybrid offspring from matings between hemiclonal hybrid waterfrogs suggest occasional recombination between clonal genomes

The hemiclonal waterfrog Rana esculenta, a hybrid between R. ridibunda and R. lessonae, eliminates the lessonae genome from the germline and clonally transmits the ridibunda genome (hybridogenesis). Such genomes are prone to accumulate deleterious mutations, which may explain why offspring from matings between hybrids are typically inviable. Here I present field data from a population for which experimental crossings showed that some R. esculenta pairs produce viable R. ridibunda offspring. I demonstrate: (1) that R. ridibunda metamorphs are also produced and survive under natural conditions; (2) that their genotypes are consistent with combinations of clonal ridibunda genomes found in hybrids; and (3) that all R. ridibunda are female. These females possibly recombine the clonal genomes they inherited and, upon mating with syntopic R. lessonae, produce new hemiclones with novel combinations of alleles. Hence, occasional recombination between otherwise clonal ridibunda genomes seems plausible and may provide an escape from the evolutionary dead end they were proposed to be trapped in.