As global climate change alters seasonal and environmental cues, many organisms are shifting their phenology. Phenological shifts early in an organism’s life history may be particularly important as these shifts could alter the timing and circumstances for all subsequent life history events. However, if organisms are able to compensate for shifting phenology, a shift at one stage may not affect later events. The energy required to compensate for shifts in the timing of life history events might require organisms to make trade-offs between rates of growth and development. Wood frogs (Rana sylvatica) have shifted their breeding two weeks earlier, on average, as climate change has increased winter temperatures over the past century. To examine the effects of phenological shifts in early developmental stages on subsequent life events, we manipulated aquatic temperature to create frog egg masses that hatched early or late. At hatching, we transferred the frog larvae to experimental ponds. In the experimental ponds, we manipulated food availability to test for the effects of normal or additional resources on developmental trade-offs. We then tracked time to metamorphosis and size at metamorphosis for all larvae.
Results/Conclusions
Egg temperature significantly affected the amount of time to hatching and the amount of time from hatch to metamorphosis. Eggs in the cool treatment hatched 6.5 days before the eggs in the warm treatment. However, at metamorphosis, that difference had decreased to 0.5 days. Therefore, larvae from cooled egg masses had accelerated their developmental rate to “catch up” to warm egg masses by metamorphosis. Mass at metamorphosis was significantly affected by the interaction of the egg temperature and larval food availability. Frogs raised in the warm egg treatment with normal larval food had the lowest metamorphic mass while frogs raised in the same egg treatment with added larval food had the highest metamorphic mass. Our results suggest that wood frogs are able to compensate for delayed hatching in the larval stage. However, the aquatic temperature they experience as eggs and the amount of resources available to them as larvae interact to affect size at metamorphosis. In the context of climate change induced phenological shifts, organisms may be able to compensate for changes to life history timing early in development but those shifts may alter growth.