STORZ, Brian L.: Investigating the Evolution of Polyphenism in North American Spadefoot Toads Using Phylogentic Inference

Some North American spadefoot toads exhibit a striking morphological and behavioral polyphenism. Upon ingesting fairy shrimp or a dead conspecific, larvae may develop a carnivorous phenotype. The carnivore phenotype has an enlarged jaw musculature, a thickened beak, amongst other phenotypic changes, and may cannibalize conspecifics. Polyphenism is thought to be adaptive and may have been one of the most influential life history characters in the evolution of North American spadefoot toads. In order to understand the relationship between the evolution of polyphenism and the evolution of spadefoot toads, it is essential to investigate the evolution of polyphenism in a phylogenetic context. In this preliminary study I examine the evolution of polyphenism using the most recent spadefoot phylogeny. I will discuss the ancestral condition of the spadefoot toads, the polarity of the trait, and the corresponding gain or loss of the character in the extant taxa. Answering these questions will allow hypotheses regarding the role of polyphenism in the adaptive evolution of spadefoot toads.