Discovery of sympatric cryptic species within Gekko hokouensis (Gekkonidae: Squamata) from the Okinawa Islands, Japan, by use of allozyme data

Abstract

An electrophoretic survey of samples of the gekkonid lizard, Gekko hokouensis, from the East Asian islands demonstrated that two genetically divergent, but morphologically almost identical, entities occur on five islands of the Okinawa Group, Ryukyu Archipelago, Japan. These entities, while sharing all of the external character states diagnostic of G. hokouensis, exhibited fixed allele differences at six to eight out of 30 loci examined and great overall genetic distances [Nei's (1978) D = 0.489-0.654]. On Kumejima and Tonakijima Islands of the Okinawa Group, the two entities were collected together from identical microhabitats. These results indicate that the two entities represent separate biological species. Genetic comparisons of these two cryptic species from the Okinawa Group with 'G. hokouensis' from other island groups revealed that one occurs broadly in the insular region of East Asia, whereas the other is restricted to the Okinawa Group. Implications of the present findings for the morphological evolution of 'G. hokouensis' are also discussed.