Butterfly lizards of the genus Leiolepis (Agamidae) are widely distributed in coastal regions of Southeast
Asia and South China, with the Reevese’s Butterfly Lizard Leiolepis reevesii having a most northerly distribution
that ranges from Vietnam to South China. To assess the genetic diversity within L. reevesii, and its
population structure and evolutionary history, we sequenced 1004 bp of cytochrome b for 448 individuals
collected from 28 localities covering almost the whole range of the lizard. One hundred and forty variable
sites were observed, and 93 haplotypes were defined. We identified three genetically distinct clades,
of which Clade A includes haplotypes mainly from southeastern Hainan, Clade B from Guangdong and
northern Hainan, and Clade C from Vietnam and the other localities of China. Clade A was well distinguished
and divergent from the other two. The Wuzhishan and Yinggeling mountain ranges were important
barriers limiting gene exchange between populations on the both sides of the mountain series,
whereas the Gulf of Tonkin and the Qiongzhou Strait were not. One plausible scenario to explain our
genetic data is a historical dispersion of L. reevesii as proceeding from Vietnam to Hainan, followed by
a second wave of dispersal from Hainan to Guangdong and Guangxi. Another equally plausible scenario
is a historically widespread population that has been structured by vicariant factors such as the mountains
in Hainan and sea level fluctuations.