Unsuspected diversity and multiple origins of the frog legs imported to Switzerland for human consumption, as determined by DNA barcoding and morphology

Abstract

The frog leg industry relies on a global, largely underregulated market with potentially important ecological impact such as the uncontrolled harvest of declining wild populations and the introduction of invasive species. Here, we inferred the taxonomic nature and geographic origins of frog legs imported to Switzerland by DNA barcoding. Out of 34 samples, we retrieved eight distinct lineages attributed to five species from four genera, namely Hoplobatrachus rugulosus from Vietnam, Fejervarya cancrivora from Indonesia (invasive on several Pacific islands), two phylogeographic lineages of Limnonectes macrodon from Western and Central Java, L. kadarsani from eastern Indonesia, and three phylogeographic lineages of Pelophylax ridibundus from northern and central southern Turkey (invasive in Western Europe). Only the first two species were correctly declared, which is particularly problematic to track down harvests of the declining and geographically restricted Limnonectes taxa. In this respect, we show that the three Asian genera can be reliably distinguished by basic measurements of the frog legs, which could be used in future forensic controls. Our study calls for more stringent international regulations of the frog trade, including shipment monitoring to document the relative abundance of harvested species and ensure the sustainability of their wild populations.