1.For animals with complex life cycles, conditions in the larval environment can have important effects that persist after metamorphosis. These carry-over effects may influence juvenile growth plasticity and have important fitness consequences. 2. Small juvenile red-eyed treefrogs, Agalychnis callidryas, grow faster than larger ones. We examined to what extent this growth pattern is due to carry-over effects of intraspecific larval competition. In particular, we assessed larval gut plasticity and determined whether carry-over effects could persist given the extensive gut remodelling that occurs when herbivorous larvae transition to carnivorous juveniles. 3. We reared larvae in mesocosms at low, medium and high densities and measured the size of both larval and juvenile guts, livers and fat bodies. We also monitored the timing of the onset of juvenile feeding post-metamorphosis and, after the onset of feeding, we measured intake rate and mean diet retention time. Finally, we measured juvenile metabolic rates to determine whether any organ size plasticity contributed to metabolic carry-over effects. 4. Larval density had strong effects on larval morphology with higher densities increasing gut length and decreasing liver and fat body sizes. The effects of this plasticity carried over postmetamorphosis. High larval densities produced smaller juveniles with proportionately longer guts and extremely small livers and fat bodies. There were no apparent carry-over effects on size-specific metabolic rate. 5. Differences in larval density were also associated with differences in post-metamorphic feeding. Small juveniles from high larval densities began feeding even before metamorphosis was complete, whereas large juveniles from low larval densities experienced a significant 2-week delay. Although juvenile body mass varied over threefold across treatments, once feeding was initiated, neither intake nor mean diet retention time scaled with body size. 6. Overall, high larval densities produced small juveniles with very low lipid reserves that may have stimulated hyperphagia relative to larger juveniles. Longer guts carried over from the larval stage could facilitate this by allowing small juveniles to elevate intake without sacrificing diet retention time. Patterns of intake coupled with differences in the onset of feeding explain the size-dependent growth pattern previously reported in this and other species.

Many animals with complex life cycles can cope with environmental uncertainty by altering the timing of life history switch points through plasticity. Pond hydroperiod has important consequences for the fitness of aquatic organisms and many taxa alter the timing of life history switch points in response to habitat desiccation. For example, larval amphibians can metamorphose early to escape drying ponds. Such plasticity may induce variation in size and morphology of juveniles which can result in carry-over effects on jumping performance. To investigate the carry-over effects of metamorphic plasticity to pond drying, we studied the Túngara frog, Physalaemus pustulosus, a tropical anuran that breeds in highly ephemeral habitats. We conducted an outdoor field mesocosm experiment in which we manipulated water depth and desiccation and measured time and size at metamorphosis, tibiofibula length and jumping performance. We also conducted a complimentary laboratory experiment in which we manipulated resources, water depth and desiccation. In the field experiment, metamorphs from dry-down treatments emerged earlier, but at a similar size to metamorphs from constant depth treatments. In the laboratory experiment, metamorphs from the low depth and dry-down treatments emerged earlier and smaller. In both experiments, frogs from dry-down treatments had relatively shorter legs, which negatively impacted their absolute jumping performance. In contrast, reductions in resources delayed and reduced size at metamorphosis, but had no negative effect on jumping performance. To place these results in a broader context, we review past studies on carry-over effects of the larval environment on jumping performance. Reductions in mass and limb length generally resulted in lower jumping performance across juvenile anurans tested to date. Understanding the consequences of plasticity on size, morphology and performance can elucidate the linkages between life stages.

Aim Understanding the scales over which land use affects animal populations is critical for conservation planning, and it can provide information about the mechanisms that underlie correlations between species distributions and land use. We used a citizen science database of anuran surveys to examine the relationship between road density, land use and the distribution of frogs and toads across spatial scales and regions of the United States.

For organisms with complex life cycles, conditions experienced during early life stages may constrain later growth and survival. Conversely, compensatory mechanisms may attenuate negative effects from early life stages. We used the spotted salamander, Ambystoma maculatum, to test how aquatic larval density and terrestrial moisture influence juvenile growth, food intake, evaporative water loss and water reuptake rates, and corticosterone levels. We conducted an outdoor mesocosm experiment to manipulate larval density and transferred metamorphosed salamanders into low and high terrestrial moisture treatments in laboratory terrariums. After the larval stage, high-density salamanders were significantly smaller and had higher corticosterone release rates than those from low-density treatments. Salamanders in the low terrestrial moisture treatment consumed fewer roaches, had lower mass-specific growth rates, higher water reuptake, and higher corticosterone release rates than salamanders in high terrestrial moisture treatments. Across moisture treatments, smaller salamanders had higher mass-specific growth rates than larger salamanders. Our results suggest that salamanders can partially compensate for competition in the larval aquatic habitat with increased growth as juveniles, but this response is dependent on terrestrial habitat quality. Thus, the persistence of early life stage effects can be an important, yet context-dependent, component of amphibian life cycles.

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