Naming structures and qualifying properties of anuran bioacoustical signals: a call for a homology-based nomenclature and equality for quantitative data

There is a significant interest for using call features in taxonomic and systematic studies. However, the indiscriminate use of alternative terms for the acoustic structures has precluded reliable comparisons among species without directly checking recordings of all compared species. Recent attempts of nomenclature standardization have focused on term and structure definitions instead of homology. Here, we argue that application of nomenclatural propositions based on universal similarities is pragmatically difficult (likely impossible) and, most importantly, inaccurate regarding to assessment of homology. If homology is not properly assessed, nomenclature can lead to artificial groupings, which can hamper our understanding of the natural world. As a solution, we propose a guideline to first assess homology correspondence and then apply adequate terms to bioacoustical structures. This assessment follows the same homology criteria used to other phenotypical structures, such as morphological ones, and their successful application depend on the comprehension of the acoustic characteristics of the structures and on sampling intermediate forms. Additionally, we point out that there is no biological difference between traits presented qualitatively or quantitatively, and, some of the issues assumedly related to quantitative features are actually related to polymorphism and overlap of trait variation between taxa.