Kinship influences the metamorphic traits of Asiatic toad ( Bufo gargarizans ) larvae, in Central China

Kin recognition has been selected by natural selection because it can enhance the chances of cooperation among close relatives, but it could also be an accidental consequence of other life-history processes. In this study, we carried out experiments by using Asiatic toad tadpoles (Bufo gargarizans) to evaluate the hypothesis that: (1) individuals can use waterborne chemical cues or combine other possible cues to communicate kinship identity when exposed to kin during early ontogeny; (2) unfamiliar siblings (or familiar non-siblings) should have similar growth with unfamiliar non-siblings because the former is not able to identify their relatives (or may not consider familiar non-siblings as kin); (3) the familiar siblings may obtain a more equal resource share in populations of siblings, thus size variation is weak. The first and second predictions were partially better supported: kinship had a positive effect on tadpole growth, obtained larger mass at metamorphosis, and increased survival, but development time was longer than that of unfamiliar non-siblings. Further, the growth of unfamiliar siblings and familiar non-siblings was different from that of familiar siblings, suggesting that Asiatic toad tadpoles lose kin-recognition ability when isolated across the embryonic stage or may not be considered as siblings when exposed to water from non-sibling groups during early embryonic development. Thus, besides chemical cues, Asiatic toad tadpoles need to combine other possible modalities to communicate kinship identity. The third prediction was supported weakly. Therefore, our results suggest that exposure to kin during early embryonic development is essential for altering kin-recognition ability. More importantly, familiar sibling groups can be expected to develop slower and spend more time in the water, allowing more time for feeding and growth, which is consistent with kin selection theory, suggesting that natural selection should drive the evolution of mechanisms that minimize the competitive intensity between sibling groups.