, Volume 141, Issue 3, pp 402-410

First online:

Reassessment of the environmental mechanisms controlling developmental polyphenism in spadefoot toad tadpoles

  • Brian L. StorzAffiliated withDepartment of Biological Science, Florida State University Email author 

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Identifying the environmental mechanism(s) controlling developmental polyphenism is the first step in gaining a mechanistic and evolutionary understanding of the factors responsible for its expression and evolution. Tadpoles of the spadefoot toad Spea multiplicata can display either a “typical” omnivorous or a carnivorous phenotype. Exogenous thyroxine and feeding on conspecific tadpoles have been accepted as triggers for development of the carnivorous phenotype on the basis of a series of studies in the early 1990s. I repeated the thyroxine and conspecific-feeding assays and demonstrated that neither exogenous thyroxine nor feeding on conspecifics induces the carnivorous phenotype. Previous researchers used simple ratio statistics to argue that field-collected carnivores and thyroxine-treated tadpoles are similar, and my results supported these claims if I used the same simple ratio methodology. However, investigation of trait developmental trajectories and allometries for field-collected carnivores and thyroxine-treated and conspecific-fed tadpoles show that these phenotypes are profoundly different.


Thyroxine Spea multiplicata Polyphenism Carnivore Omnivore