Abstract
We karyotyped five species of the agamid genus Gonocephalus, G. chamaeleontinus, G. liogaster, G. bellii, G. grandis (from Peninsular Malaysia), and G. robinsonii. Of these, karyotypes of the first four species had several chromosomal characteristics exclusively shared with the previously reported karyotypes of G. miotympanum and G. grandis (from Borneo), such as the diploid chromosome number (42) and the presence of 22 biarmed macrochromosomes. This seems to support the monophyly of those four species and G. miotympanum, probably along with some other species of the genus not yet karyotyped. This hypothesis is premised on our finding of distinct chromosomal characteristics that are indicative of highly derived states in the agamid karyotypes. The karyotype of G. robinsonii, while remarkably different from other congeneric karyotypes in exhibiting much smaller diploid (32) and biarmed macrochromosome numbers (12), share these and other chromosomal characteristics with several Australian species. It seems unlikely for the karyotype of G. robinsonii to directly emerge from other congeneric karyotypes or vice versa. We conclude that the inclusion of this species in Gonocephalus would render the genus paraphyletic.
