Cryptic Taxonomic Diversity in Two Broadly Distributed Lizards of Thailand (Mabuya macularia and Dixonius siamensis) as Revealed by Chromosomal Investigations (Reptilia: Lacertilia)

Abstract

Karyological surveys were made for two common lizards,
Mabuya macularia and Dixonius siamensis, in Thailand. Of the M.
macularia specimens karyotyped, the one from Mae Yom, northwestern
Thailand, had 2n=38 chromosomes in a graded series as previously reported
for a specimen from southwestern Thailand. The other specimens, all from
eastern Thailand, however, invariably exhibited a 2n=34 karyotype
consisting of four large, and 13 distinctly smaller chromosome pairs. Of the
D. siamensis specimens, on the other hand, those from eastern Thailand
invariably exhibited a 2n=40 karyotype, whereas three males and one female
from Mae Yom had 2n=42 chromosomes. Distinct chromosomal variation
was also observed within the Mae Yom sample that may reflect a ZW sex
chromosome system. These results strongly suggest the presence of more
than one biological species within each of those “broadly distributed
species”. This further argues the necessity of genetic surveys for many other
morphologically defined “common species” in Thailand and its vicinity in
order to evaluate taxonomic diversity and endemicity of herpetofauna in this
region appropriately.