Moreira, F.D., Marques, R., Sousa, M. & Rebelo, R. (2017) Breeding in both lotic and lentic habitats explains the invasive potential of the African clawed frog (Xenopus laevis) in Portugal.Aquatic Invasions, 12(4), 565-574. DOI:10.3391/ai.2017.12.4.12 (IF2016 2,069; Q2 Marine & Freshwater Biology)
The African clawed frog is a successful invader in several countries throughout the world. Although it may be found in both lentic and lotic habitats, its use of both habitats for breeding has not been documented. Nonetheless, in its Portuguese invasive range this frog was found to breed in small streams, as well as in ponds. We recorded all the sites where Xenopus laevis bred during a 7-year period (2010–2016) in the entire Portuguese invasive range. In 2015 and 2016, we measured snout-vent length of 970 tadpoles from eleven sites, and the size and body condition at the end of metamorphosis of 91 metamorphs from four sites. To assess the size at which reproductive investment begins, we dissected and weighed the gonads of 409 juveniles and small adults. We found that the species can produce metamorphs in both habitats, but their numbers were much higher in lentic sites. Furthermore, tadpoles and metamorphs from lentic sites were much larger than those from lotic sites. Body condition of metamorphs was similar across all sites. Gonad development was size-dependent, and we estimate that larger metamorphs from lentic sites will mature sooner and may reproduce in the following year, while smaller metamorphs will need an extra year. Our results suggest that while lentic sites are most likely to be responsible for population booms, the hitherto unknown reproduction in lotic sites may contribute to the maintenance of the invasive population even in the absence of lentic sites.