Simple observations with complex implications: What we have learned and can learn about parental care from a frog that feeds its young

The discovery of a trait in a new lineage, especially one distantly related to those already known to express the trait, affords the opportunity to test and refine existing hypotheses for that trait's evolution and to develop new ideas. Peter Weygoldt made such a discovery, reporting the first instance of a frog that feeds its young and, even more remarkably, the first instance of dependent tadpoles that perform solicitation displays before being fed (1980. Behav. Ecol. Sociobiol. 7, 329-332). This discovery has featured prominently in taxonomic surveys of parental care and offspring-parent communication, but more importantly has expanded the questions that are and can be asked about these topics. I review the advances in knowledge of the natural history of the frog Weygoldt studied as well as the theoretical frameworks that inform and are informed by these advances. I highlight ideas and information about parental care in O. pumilio that are central to broadly understanding the evolution of parental care. Our understanding of the evolution of sex roles will, for example, improve by following Weygoldt's finding that male O. pumilio care for clutches with detailed accounting of the costs and benefits mothers and fathers might pay for performing this task. When a parent transports tadpoles from a terrestrial clutch to an aquatic nursery, it sets the stage for sibling competition for this resource (transport), and proximate and ultimate tests for such conflict will inform more general ideas about how conflict and cooperation shape nuclear families. That the begging displays of tadpole O. pumilio are performed in solitary nurseries makes this species uniquely suited to test honest-signaling models for the evolution of offspring-parent communication. By detailing the implications and possibilities stemming from Weygoldt's work, I hope to inspire readers to follow Weygoldt's lead and his example of careful and detailed observation.