Fig. 1
Map of the six geographic samples for the four-eyed sleeper (with the two-letter abbreviations of their localities given in parentheses). This map is rendered with ODV v4.7.3 (Schlitzer 2002). Shallow seabeds with depths of <100 m, which were exposed during the major glaciations of the last one million years (e.g., Marine Isotope Stage 12), are denoted by the offshore shading (Voris 2000; Railsback et al. 2015), whereas the spring and summer directions of the South China Sea Surface Current and Kuroshio Branch Current through the Taiwan Strait are represented by the arrows (Jan et al. 2002). (Inset) Two females from WZ and one female from XM with final individual identifications of SCS, ECS, and SCS, respectively (see text). The body sizes of these three females approximate the mean SL of their sympatric SCS and ECS groups at WZ and allopatric SCS group at XM, respectively. Thus, their size differences illustrate that SL of SCS individuals varies geographically such that SCS individuals in sympatry are bigger than ECS specimens, but are of similar size in allopatry. Furthermore, the ECS female from WZ illustrates the presence of dark costal stripes, which is the second morphological trait of this study
