Reassessment of the environmental mechanisms controlling developmental polyphenism in spadefoot toad tadpoles.
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.
Department of Biological Science, Florida State University, Tallahassee, FL 32306-1100, USA. bstorz@bio.fsu.edu
Brian L
BL
Storz
D000222:Adaptation, Physiological; D000818:Animals; D001001:Anura / Q000033:anatomy & histology* / Q000254:growth & development*; D005075:Biological Evolution; D004032:Diet; D005260:Female; D007814:Larva / Q000254:growth & development; D008297:Male; D010641:Phenotype; D011235:Predatory Behavior; D013974:Thyroxine / Q000494:pharmacology
D013974:Thyroxine