FEEDING-BEHAVIOR, FOOD-CONSUMPTION, AND GROWTH EFFICIENCY OF HEMICLONAL AND PARENTAL TADPOLES OF THE RANA-ESCULENTA COMPLEX

1. Clonally reproducing species are often assumed to lack sufficient g enetic variability to evolve specific local adaptations to cope with e nvironmental perturbation and competition from sexual species. Yet, ma ny asexuals are extremely successful judged by abundance and wide rang e, suggesting high competitive abilities in resource exploitation. 2. In this study, food use and its effects on larval growth in a water fr og system consisting of the two parental sexual species, Rana lessonae (Camerano 1882) and Rana ridibunda (Pallas 1771), and three different coexisting hemiclones of their hybrid, Rana esculenta (Linnaeus 1758) were investigated. 3. R. esculenta tadpoles spent 18.6% more time fee ding than did tadpoles of either parental species, but feeding time wa s not affected by interspecific mixture. 4. R. esculenta tadpoles cons umed 50.8% more food over the whole test period than did tadpoles of t he two parental species. 5. R. esculenta tadpoles exhibited higher gro wth rates than did tadpoles of either parental species. 6. R. lessonae tadpoles had the highest and R. ridibunda tadpoles the lowest growth efficiencies with the R. esculenta tadpoles ranging between the two pa rentals. 7. The results obtained indicate that hemiclonal hybridogenet ic R. esculenta tadpoles display significant phenotypic variation amon g coexisting hemiclones as well as outperform tadpoles of the parental sexual species R. lessonae and R. ridibunda. The primary mechanism fo r success of the hybrid tadpoles is probably behavioural, through incr eased feeding time and food consumption, and not physiological via gro wth efficiency.