Ongoing invasions of the African clawed frog, Xenopus laevis: a global review

We conducted a literature review on the current status of all known extralimital populations of the African clawed frog, Xenopus laevis, to identify commonality in invasion pathways, lag between discovery and introduction, and whether old populations are in decline. Further, we investigated which locations are vulnerable to future establishment using geospatial data (1,075 native and 124 invasive records) in a Maxent model developed with data from the Worldclim database. We found introductions of X. laevis to be continuous over the last 50 years and invasions to be ongoing on four continents: Asia, Europe, North and South America. Invasion pathways were related to scientific use and the pet trade, with high rates of deliberate release followed by a lag of 2-25 years to first reports. No populations were found to be declining although some have been extirpated. Optimal uninvaded bioclimatic space was identified in central Mexico and southern Australia, while larger suitable areas were found in southern South America and southwestern Europe. Xenopus laevis is a cryptic invasive species that is likely to increase its invasive distribution, through new introductions and by the spread of ongoing invasions. Many more invasive populations are likely to exist than are currently recognised and reducing invasive potential will largely rely on education of those involved with their captive care.