Leg length as a carryover effect of development time in spadefoot toads

Development time is a key characteristic that can impact the morphology and fitness of an organism. This is especially true in amphibians that develop as larvae in aquatic habitats before making the transition to land as adults. However, measuring development time is not always feasible, especially in natural populations where access to developing individuals is limited. In these cases, identifying proxies for development time can become important tools for studying ecological and evolutionary effects of development time. Previous work in the anuran families Scaphiopodidae and Pelobatidae suggested that longer development time for a given species is correlated with longer relative leg lengths as adults. This carryover effect of development time into adulthood was presumed to be a general pattern across all species within these families. I examined if the relationship held both within and between two closely related species in the Scaphiopodidae. To do so, I measured subadult leg length across different species that differed in development time. I also measured development time and leg length from an experiment in which tadpoles were bred and raised under controlled conditions. I found significant carryover effects of development time on leg morphology, but with opposite conclusions than those of previous work. My results indicate that morphology can be used to indicate development time, but that carryover effects can be reversed evolutionarily within taxonomic clades. Caution must therefore be exercised when extrapolating the expected direction of carryover effects across different species.