Competition induces silver spoon effects in developing anuran larvae

Abstract

Early life conditions can have lifelong impacts on survival and fitness. Silver spoon effects occur when favorable early life conditions provide advantages through adulthood, even if conditions worsen. Alternatively, compensatory growth allows organisms initially reared in unfavorable conditions to grow more quickly than expected should conditions improve. We examined these possibilities in the American Toad, Anaxyrus americanus, by rearing larvae in low and high competition environments and then transferring them to either high- or low-resource levels. We measured growth one-week post-transfer and toadlet size after metamorphosis. We also dissected larvae and toadlets from each treatment to examine effects on organ size. Before transfer, larvae reared with low competition grew significantly faster than those reared with high competition. Consistent with the silver spoon hypothesis, these larvae ate significantly more food, continued to grow faster post-transfer, and metamorphosed into larger toadlets with smaller livers and larger guts than those initially reared with high competition, despite having the same food availability within a resource level. Overall, our study demonstrates that larvae initially reared in favorable conditions maintain a growth advantage through metamorphosis even if resource levels decline. Future studies should explore the effects of this advantage post-metamorphosis and into adulthood.