Little attention has been paid to the consequences of the last landbridge between Africa and Sicily on Mediterranean biogeography. Previous paleontological and scarce molecular data suggest possible faunal exchange later than the well-documented landbridge in the Messinian (5.3 My); however, a possible African origin of recent terrestrial Sicilian fauna has not been thoroughly tested with molecular methods. To gain insight into the phylogeography of the region, we examine two mitochondrial and two nuclear markers (one is a newly adapted intron marker) in green toads (Bufo viridis subgroup) across that sea barrier, the Strait of Sicily.

The worldwide spread of invasive species is considered to be one of the main causes of global amphibian declines and the loss of biodiversity in general. The African Clawed Frog, Xenopus laevis, shows a strong ability to establish populations and invade various geographic regions. In 2004 X. laevis was found in Sicily for the first time. The Sicilian population is probably the largest in Europe with a range of about 225 km2 in an area characterized by numerous agricultural ponds. This high density of ponds has potentially facilitated the dispersal of X. laevis. The frogs can move far from rivers or watercourses by utilizing the ponds as suitable "islands". The analysis of their diet shows that the aquatic larvae of nektonic insects comprise the major portion in terms of mass while small planktonic crustaceans are the most numerous component. There is a significant difference between the diet of adults and juveniles.

African clawed frogs of the widespread polytypic species Xenopus laevis Daudin, 1802 (ranging large parts of sub-Saharan Africa) have been spreading since the 1940s, and have established reproductive populations in Europe, Asia and the Americas, where they can have negative impact as competitors of native amphibians and as disease vectors for chytridomycosis or ranaviruses. Here we use two mitochondrial (cytochrome b, 16S rDNA) and one nuclear (RAG 1: Recombination Associated Gene 1) DNA markers to infer the potential origin of invasive clawed frogs from Sicily that represent the largest invasive population in Europe. Identical mtDNA haplotypes match with those of Xenopus laevis, and Sicilian clawed frogs very probably belong to a lineage from the Cape Region of South Africa, most likely originating from a laboratory stock. Nuclear data support this conclusion. Identical mtDNA sequences (cyt b, 16S) of frogs sampled across their range in Sicily suggest the occurrence of a single source population and a potential bottleneck at their release, but faster evolving multilocus nuclear data (microsatellites, SNPs) on the population genetics would be important in the future to better support this hypothesis.