The status of natural hybridization between the two Japanese geckos, Gekko tawaensis and Gekko japonicus, was surveyed by use of 15 diagnostic allozyme loci. Of 438 specimens examined, 9 were identified as Fl, 1 was a first backcross with G. japonicus, and 15 were identified as more successive generations. Hybridizations were detected at 7 of the 15 localities interspersed throughout a broad sympatric area of the two species, forming a mosaic hybrid zone. A comparison of species–hybrid composition between 2-year samples from a single locality and a 5-year interval showed no evidence for progressive introgression or establishment of a hybrid swarm, despite constant emergences of Fl hybrids. Nonprevalence of the hybrid genotypes was also indicated by the analysis using hybrid index scores for all other localities examined. These results suggest that strong selection acts against hybrid genotypes. Morphological features of hybrid individuals were also provided.
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ACKNOWLEDGMENTS
We thank H. Saito and M. Takeshima for their help in field collection. Financial support for this study was provided by a Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists (9413 to MT) and a Grant-in-Aid from the Japan Ministry of Education, Science, Sports, and Culture (C-11833013 to HO), as well as by a Grant for Biodiversity Research of the Twenty-First Century COE (A14).
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APPENDIX: DEFINITIONS OF MORPHOLOGICAL CHARACTERS
APPENDIX: DEFINITIONS OF MORPHOLOGICAL CHARACTERS
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TD, the number of irregular rows of dorsal tubercles counted transversely at mid-body.
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TS, the presence or absence of tubercles on shank.
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IN, the size of internasal in relation to the granule immediately posterior to it: small (S, smaller than 1.2 times), slightly enlarged (SL, as large as or larger than 1.2 times but not reaching 1.5 times), or enlarged (L, as large as or larger than 1.5 times).
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PPM, condition of posterior scale of the postmentals, divided or undivided.
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CS, the mean number of cloacal spurs on both sides.
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PP, the number of preanal pores in males.
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Toda, M., Okada, S., Hikida, T. et al. Extensive Natural Hybridization Between Two Geckos, Gekko tawaensis and Gekko japonicus (Reptilia: Squamata), Throughout Their Broad Sympatric Area. Biochem Genet 44, 1–17 (2006). https://doi.org/10.1007/s10528-006-9010-9
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DOI: https://doi.org/10.1007/s10528-006-9010-9