This website is devoted to the INVAXEN project, a collabaration between research groups at the CNRS, Paris, the Royal Belgian Institute of Natural Sciences, Brussels (RBINS), the Zoologisches Forschungsmuseum Alexander Koenig, Bonn (ZFMK), and the Fundacao da Faculdade de ciencias da Universidade de Lisboa, Lisbon (FFCUL). The project is conducted in close collaboration with Dr. John Measey (Center for Invasive Biology, Stellenbosch University, South Africa) allowing a comparison of native with invasive population of the species.

The project is funded through a BIODIVERSA call and aims to investigate the INVAsive biology of XENopus laevis in Europe (INVAXEN) by studying the ecology and impact of X. laevis and by building predictive models. Xenopus laevis is one of the world's most widely distributed amphibians with invasive populations having become established on four continents due to both accidental escape and voluntary release of laboratory animals [1]. The impacts of invasive X. laevis on native populations of amphibians and fish has been documented in several cases [2-5], yet systematic studies focusing not only on vertebrate but also invertebrate communities are lacking. Moreover, X. laevis has been implicated in the global transmission of disease including chytridiomycosis, a disease cited as one of the principal causes for the global decline in amphibians [6-8]. A recent study suggested that a global level the invasion potential of X. laevis has been severely underestimated with many areas potentially being susceptible to the invasion of X. laevis [1]. The presence of the species in laboratories world-wide and being one of the most commonly traded amphibians [9] makes it one of the most critically important species to follow. This species is of concern in Europe as it is known to be invasive in at least four countries (France, Portugal, Italy and the U.K.) and the suggested suitable climatic space covers over one million square kilometers making this species of pan-European concern [1].

We propose to study the invasive biology of X. laevis by bringing together a team of experts from four countries that will provide complementary data to better understand the biology, dispersal patterns, physiology, impact on local populations and its invasive potential. Moreover, we will evaluate an ongoing eradication program of this species in France and Portugal. Three work packages devoted to studying the ecology, physiology, and population genetics of both invasive and native populations will be integrated in a fourth work package where these data will be incorporated into predictive species distribution models that take into account the biology of the species.

  • A first work package will study the biology of X. laevis in its native and introduced ranges, will evaluate the impact of X.laevis on local vertebrate and invertebrate communities, will document the presence/absence of chytridiomycosis in known invasive populations, and will follow up and improve upon an ongoing eradication program that will inform future policy makers in deciding how to arrest the ongoing invasion in Europe.

  • A second work package will study the temperature and hydric (humidity) dependence of locomotion in native and invasive populations, will conduct mark-recapture and telemetry studies to assess mobility and movement patterns in the wild to determine the extent of the distribution of the invasive populations around known sites.

  • The third work package will quantify genetic diversity of native and invasive populations and will quantify gene flow within and between populations using microsatellite markers.

  • The final work package will integrate the data on movement patterns, gene flow and physiology to model potential future distribution of the species in two countries with invasive populations at a landscape level and will predict the potential future spread of this species outside of its current invasive range under different scenarios of global change incorporating temperature and rainfall data. This integrative project has a pan-European dimension and may serve as a model for the study of invasive vertebrate species.

    BiodivERsA is very happy to announce the release of its third animated video ( presenting the results of the INVAXEN research project. The BiodivERsA Prize is awarded on a yearly basis to showcase the achievements of BiodivERsA-funded projects that have produced excellent science with concrete impacts for policy and/or society. The Belgian Biodiversity Platform & BiodivERsA led the production of this video, along with the INVAXEN project researchers and the video production company, Squarefish.


    [1] Measey, G.J., D. Rödder, S.L. Green, R. Kobayashi, F. Lillo, G. Lobos, R. Rebelo and J.-M. Thirion (2012) Ongoing invasions of the African clawed frog, Xenopus laevis: a global review. Biol. Invasions
    [2] Crayon, J.J. (2005) Species account: Xenopus laevis. In: Lannoo M.J. (ed.) Amphibian declines: the conservation status of United States Species. University of California Press, Berkeley, pp. 522-525.
    [3] Lafferty, K.D. and C.J. Page (1997) Predation on the endangered tide-water goby, Eucyclogobius newberryi, by the introduced African clawed frog, Xenopus laevis, with notes on the frog's parasites. Copeia 1997: 589-592.
    [4] Lillo, F., F.P. Faraone and M. Lo Valvo (2011) Can the introductions of Xenopus laevis affect native amphibian populations? Reduction of reproductive occurrence in presence of the invasive species. Biol. Invasions 13: 1533-1541.
    [5] Rebelo, R., P. Amaral, M. Bernardes, J. Oliveira, P. Pinheiro and D. Leitao (2010) Xenopus laevis (Daudin, 1802), a new exotic amphibian in Portugal. Biol. Invasions 12: 3383-3387.
    [6] Robert, J., L. Abramowitz, J. Gantress and H.D. Morales (2007) Xenopus laevis: a possible vector of Ranavirus infection? J. Wildl. Dis. 43: 645-652.
    [7] Schmeller, D.S., A. Loyau, T. Dejean and C. Miaud (2011) Using amphibians in laboratory studies: precautions against the emerging infectious disease chytridiomycosis. Lab. Anim. 45: 25-30.
    [8] Skerratt, D.S., L. Berger, R. Speare, S. Cashins, K.R. McDonald, A.D. Phillott, H.B. Hines and N. Kenyon (2007) Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. EcoHealth 4: 125-134.
    [9] Herrel, A. and A. van der Meijden (2014) An analysis of the live reptile and amphibian trade in the U.S.A. compared to the global trade in endangered species. Herp. J. 24: 103-110.