Description of Two New Species of the Genus Gekko (Squamata: Gekkonidae) from the Tokara and Amami Island Groups in the Ryukyu Archipelago, Japan

Populations of the genus Gekko from three southern islands of the Tokara Group, Ryukyu Archipelago are known to be unique in lacking distinct preanal pores even in adult males. Recently, we found an almost identical morphotype from five islands of the Amami Group, where only G. hokouensis, a species having distinct preanal pores in adult males, has hitherto been recorded. To clarify the taxonomic status of these poreless geckos from the Tokara and Amami Groups, we conducted allozyme and morphological comparisons of Gekko specimens collected from these eight islands and one adjacent island. Results of the allozyme analyses showed the presence of fixed allelic differences at 7–14 loci between samples of the poreless form and sympatric G. hokouensis from each of the Amami islands, confirming their reproductive isolation. Our data further revealed the presence of two genetically divergent groups within the poreless form that are distinct from each other by fixed allelic differences at no less than 30% of loci examined. Ranges of these two groups are contiguous with each other but do not overlap on a single island. Distance analysis showed that one of the two groups is genetically much closer to G. hokouensis than to the other. These results strongly suggest that each of them represents an evolutionarily independent unit and deserves recognition as a full species. We describe these species based on a set of characters that clearly discriminate them from all other congeneric species hitherto described, and we briefly discuss their historical biogeography.

Fig. 1

Maps of the Ryukyu Archipelago (A) and its north-central part in a greater scale (B). Dashed and complete lines enclose distributional ranges of G. hokouensis and the poreless form, respectively. Arrowheads indicate islands, from which Gekko specimens examined in this study were collected: 1 = Kojima; 2 = Kodakarajima; 3 = Takarajima; 4 = Amamioshima; 5 = Kakeromajima; 6 = Ukejima; 7 = Yorojima; 8 = Tokunoshima; 9 = Kikaijima.

Fig. 2

UPGMA phenogram based on Nei's (1978) genetic distances for 15 Gekko samples from the north-central Ryukyus. Numerals correspond to those in Fig. 1.

Fig. 3

(A) Dorsal and (B) ventral views of holotype of Gekko shibatai (KUZ R52225).

Fig. 4

(A) Dorsal and (B) ventral views of holotype of Gekko vertebralis (KUZ R34204).

Fig. 5

(A) Dorsal and (B) ventral views of G. hokouensis from Tokunoshima, KUZ R55289, and (C) dorsal and (D) ventral views of Gekko vertebralis from Tokunoshima, KUZ R34001, paratype.

Contributor Notes

Associate Editor: M. J. Lannoo.

¹ Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan, E-mail: (MT) gecko@zoo.zool.kyoto-u.ac.jp. Send reprint requests to MT.

² Japan Wildlife Research Center, Shitaya 3-10-10, Taitou-ku, Tokyo 110-8676, Japan.

³ Tropical Biosphere Research Center, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.

Received: 08 Dec 2006

Accepted: 11 Sept 2007