Data from: Correlated evolution of phenotypic plasticity in metamorphic timing

Phenotypic plasticity has long been a focus of research, but the
mechanisms of its evolution remain controversial. Many amphibian species
exhibit a similar plastic response in metamorphic timing in response to
multiple environmental factors; therefore, more than one environmental
factor has likely influenced the evolution of plasticity. However, it is
unclear whether the plastic responses to different factors have evolved
independently. In this study, we examined the relationship between the
plastic responses to two experimental factors (water level and food type)
in larvae of the salamander Hynobius retardatus, using a cause-specific
Cox proportional hazards model on the time to completion of metamorphosis.
Larvae from ephemeral ponds metamorphosed earlier than those from
permanent ponds when kept at a low water level or fed conspecific larvae
instead of larval Chironomidae. This acceleration of metamorphosis
depended only on the permanency of the larvae’s pond of origin, but not on
the conspecific larval density (an indicator of the frequency of
cannibalism) in the ponds. The two plastic responses were significantly
correlated, indicating that they may evolve correlatively. Once plasticity
evolved as an adaptation to habitat desiccation, it might have relatively
easily become a response to other ecological factors, such as food type
via the pre-existing developmental pathway.