Geographic variation in the two smooth skinks, Scincella boettgeri and S-formosensis (Squamata : Scincidae), in the subtropical East Asian islands

Abstract

Scincella boettgeri and S. formosensis are two small lygosomine skinks endemic to the southern Ryukyus and Taiwan, respectively. Taxonomic separation of these two species depends on only a few external characters that are seemingly more or less variable within each species. To investigate the geographic pattern of their morphological variations, multivariate analyses were performed for 23 meristic and 16 morphometric characters in 680 specimens of S. boettgeri from 12 islands of the Miyako and Yaeyama Groups and 193 specimens of S. formosensis from ten localities in Taiwan. The canonical discriminant analysis (CDA) for samples representing local populations using meristic data completely separated the southern Ryukyu and Taiwanese assemblages, supporting their assignments to different taxa. On the other hand, the analyses using morphometric data remained their variations partially overlapping each other. Of the samples of S. boettgeri examined, the Haterumajima sample markedly varied from the others, whereas the Kaohsiung sample was somewhat divergent among the S. formosensis samples. Neighbor-joining phenograms derived from Mahalanobis distances among the samples showed branching patterns apparently inconsistent with the topographical (for S. formosensis) or putative geohistorical relationships of their localities (for S. boettgeri). This suggests that in these species external quantitative characters often rapidly vary under the influence of localized environments rather than of the passage of time after geographical isolations.