Invasions Through the Amphibian Trade: A Comparative and Unifying Framework for Species Assignments of Cryptic Brown Frogs

The wildlife trade increases the risk of global biological invasions and accurate species assignment is critical. Here, using cross-study comparisons, we quantified the efficiency of species assignment methods and confirmed the higher sensitivity of coalescent-based methods in isolating cryptic operational taxonomic units (OTUs). We then provided a framework incorporating morphometry, phylogenetic trait, species delimitation modelling and phylogeography to improve the accuracy of species identification of brown frogs (Rana) imported into the Republic of Korea. We identified three non-native species: R. chensinensis, R. amurensis and R. kukunoris, and the presence of 12 OTUs from the trade. The combined model-based OTUs and 16S phylogeny on traded and control specimens (n = 230) revealed the widespread and likely wild-harvested origins of traded Rana individuals. Our results also highlight the independent evolution of toe-webbings in Rana for the last 12.0 Mya, a key trait for species identification. With the framework for broad-scale species identification developed herein, we urge the development of trade monitoring and legislation on Rana species in northeast Asia.