Bolis, A., D. Pellitteri-Rosa & A. Bellati

Cross-specific mortality and differential occurrence of aberrant phenotypes in tadpoles of the Pelophylax kl. esculentus hemiclone assortment. pp. 127-130.

Abstract. The occurrence of morphological malformations is considered one of the factors involved in the amphibian decline and can be promoted by the reduction in genetic diversity due to inbreeding. Water frogs (gen. Pelophylax) offer a unique opportunity to shed light on the relationship between the onset of body malformations and variation in parental genomes. Indeed, members of this genus exhibit a reproductive strategy called hybridogenesis in which the resulting hybrid (klepton) is fertile and produces gametes carrying one non-recombinant parental genome. To investigate the effect of inbreeding on the development of clonal offspring, we performed in vitro crossings between identical hemiclones from the same population (Crossing 1) and distinct hemiclones from different populations (Crossing 2). Genetic variation of parental genomes was assessed by molecular diagnostic markers (mtDNA ND3; 9 microsatellites). Results showed that tadpoles generated by Crossing 1 showed a higher mortality rate (p < 0.05) and occurrence of a specific malformation (bent tail, 85%), with respect to Crossing 2, where no aberrant phenotype were observed. This study supports previous findings that identify inbreeding as a causal factor in determining offspring mortality and the expression of developmental abnormalities in amphibian populations. We also add knowledge on the genetic basis of a typical aberrant phenotype in tadpoles affecting body morphology and important life-history traits.

Key words. Morphological malformations, inbreeding, hybridogenesis, Pelophylax esculentus complex, artificial crossing, mitochondrial DNA, nuclear DNA.