Kin recognition by larval wood frogs (Rana sylvatica): effects of diet and prior exposure to conspecifics

We investigated kin recognition by larval wood frogs (Rana sylvatica) in blind laboratory experiments using spatial affinity as a recognition assay. Tadpoles reared with full-sibs displayed a significant preference for familiar full-sibs over unfamiliar non-kin, but failed to discriminate between unfamiliar full-sibs and unfamiliar paternal half-sibs. Tadpoles reared in social isolation (with or without maternal egg jelly) from the two-celled embryonic stage displayed a significant preference for unfamiliar full-sibs over unfamiliar non-kin. Tadpoles reared on a meat diet with their full-sibs: 1) exhibited a significant preference for unfamiliar full-sibs fed meat over unfamiliar non-kin fed meat, 2) failed to discriminate between unfamiliar full-sibs fed lettuce and unfamiliar non-kin fed meat, 3) exhibited a significant preference for unfamiliar non-kin fed meat over unfamiliar non-lin fed lettuce, 4) failed to discriminate between unfamiliar full-sibs fed meat and unfamiliar full-sibs fed lettuce, and 5) displayed a significant spatial preference for odors associated with meat (a familiar food) over odors associated with lettuce (an unfamiliar food). Our results, together with those of Cornell et al. (1989), indicate that the recognition cue of larval R. sylvatica has both genetic and environmental (dietary) components. Our findings establish that previous exposure to maternal egg jelly, kin, or conspecifics is not necessary for the development of kin recognition ability in larval R. sylvatica. Our results are more consistent with the self-learning of recognition cues (a form of phenotype matching) than with a recognition mechanism that involves a genetically fixed recognition template. Finally, our results indicate that increasing similarity between the recognition template and perceived cue does not necessarily result in increasing spatial affinity for kin.