Investigating the origin of transoceanic distributions: mtDNA shows Mabuya lizards (Reptilia, Scincidae) crossed the Atlantic twice
Phylogenies with even a rough time scale can be used to investigate the history of non-volant taxa with disjunct distributions in widely separated land areas that were once connected. Basic methods for doing this are discussed. A partial phylogeny of Mabuya based on mtDNA (305 bp cytochrome b, 379 bp 12S rRNA and 388 bp 16S rRNA) is used to show that this genus invaded tropical America from Africa twice in the last 9 Myr, once reaching the American mainland and once the oceanic island of Fernando de Noronha, two journeys each of at least 3000 km. In general, phylogenetic evidence for multiple invasions is less equivocal than that suggesting a single invasion, which is more prone to sampling artefacts. Two alternative hypotheses explaining the presence of Mabuya in both Africa and tropical America are refuted on the basis of molecular clock considerations, namely that the occurrence of Mabuya in these continents pre-dated their separation over 100 My ago and that it was introduced from one continent to the other by human activities. Like several other lizard groups that have made successful long-distance transmarine colonizations, Mabuya has done this on many occasions. Phylogenetic results are also compatible with a SE Asian or Australasian origin of Mabuya followed by westward expansion.(Received September 2002)
(Accepted November 2002)
Key Words: disjunct distribution; Fernando de Noronha; Mabuya; mtDNA; skinks; transmarine colonization.
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