title: Within-island speciation with an exceptional case of distinct separation between two sibling lizard species divided by a narrow stream.
abstract: Delimitation of genetic and geographic boundaries between species is a focus of evolutionary biology. In this study, we demonstrated fine-scale differentiation of Takydromus formosanus species complex comprising four insular endemics on Taiwan Island. Phylogeny and ancestral range reconstruction based on mitochondrial DNA sequences of 430 Takydromus lizards (405 lizards of this complex throughout their distribution range, and 25 lizards from 11 other species) indicated that the major branching process occurred within Taiwan, which represented a solid evidence of within-island speciation on this small island. We further demonstrated an exceptional case of a pair of sister species, T. viridipunctatus and T. luyeanus, that were separated by a narrow stream with a width of only 15m. This pattern might be one of the narrowest contact zones ever documented in terrestrial vertebrates. To evaluate the level of genetic introgression between these sister species, a fine-scale collection of another 382 lizards was conducted along a transect line across the stream. A total of 13 microsatellite markers and mtDNA genotyping was used to detect a low proportion of hybrids (5.7-9.9% from STRUCTURE, and 2.3% from DAPC). Our results indicated that the two clades are highly differentiated across this extremely short distance.
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei 116, Taiwan; Department of Entomology, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Tseng
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei 116, Taiwan.
authors.forename: Chao-Jun
authors.initials: CJ
authors.lastname: Wang
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei 116, Taiwan.
authors.forename: Shou-Hsien
authors.initials: SH
authors.lastname: Li
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei 116, Taiwan. Electronic address: fish@ntnu.edu.tw.
authors.forename: Si-Min
authors.initials: SM
authors.lastname: Lin
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial / Q000032:analysis / Q000235:genetics; D005838:Genotype; D008116:Lizards / Q000145:classification* / Q000235:genetics; D018895:Microsatellite Repeats / Q000235:genetics; D010802:Phylogeny; D011157:Population Dynamics; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: Ancestral range reconstruction; Contact zone; Fine-scale differentiation; Genetic introgression; Hybridisation; Parapatric speciation