無中文摘要

High mountain regions, also known as “sky islands” in biogeography, has gained much attention in evolutionary biology especially under the recent threats of global warming. With high level of isolation, species living in mountain peaks often have restricted gene flow between populations and form highly differentiated geographic structures. In this study, however, we aimed to demonstrate a slightly different story about how a cryptic species evolved in the mid-elevation area, and ceased the gene flow between populations on high-elevation mountain ranges. Sphenomorphus taiwanensis, a small-sized skink, is widely distributed in high mountains of Taiwan and shows potential genetic differentiation among populations. By using SNPs data from ddRADseq, we discovered a unique clade which showed great genetic divergence from the others. With congruent morphological differentiation, it should be treated as a distinct species based on species delimitation analyses. Interestingly, this species distributes in middle elevation at the saddle region between the two major mountain ranges of Taiwan, geographically separated the high-elevation populations of S. taiwanensis into two major lineages. Genetic analysis using G-phoCS indicated potential gene flow between high-elevation and mid-elevation species, but the gene flow between mountain ranges was weak among high-elevation populations. The isolation-by-resistance (IBR) analysis also illustrated that the cryptic species is the resistance for the inter-population migration of S. taiwanensis. I suggest that the cryptic species should be revealed before investigating the genetic differentiation pattern, or the pattern will be unidentified. In this study, I reveal a cryptic
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species and the pattern of genetic differentiation of S. taiwanensis in the sky islands.

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