<b>Multi-loci molecular phylogeny brings insight into systematics and evolution of genus </b><b><i>Tridentiger</i></b><b> (Teleostei: Gobiiformes)</b>

The genus <i>Tridentiger</i> Gill, 1859 is comprised of barbeled and non-barbeled species, which is considered as key character to further divide the genus. Our phylogenetic tree based on 5028-bp sequence data of six genes indicated a well-supported sister relationship between the non-barbeled <i>T. nudicervicus</i> and the barbeled <i>T. barbatus</i> and <i>T. microsquamis</i>, with <i>Papuligobius uniporus</i> as the closest outgroup for <i>Tridentiger</i>. Due to lack of significant diagnoses and the common character of tricuspid teeth, <i>Papuligobius</i> is considered a junior synonym of <i>Tridentiger</i>. Moreover, 12S rRNA K2P distance (0.0000–0.0016) between <i>T. microsquamis</i> and <i>T. radiatus</i> fall in the interval of intraspecific distances (0.0000–0.0030), much smaller than the interspecific distances (0.0122–0.1383). Therefore, <i>T. radiatus</i> should be treated as a synonym of <i>T. microsquamis</i>. K2P distances between the southern and northern lineages <i>T. barbatus</i> fall in the interval of interspecific distances in 12S rRNA, Cyt<i>b</i> and RAG1 genes, which were delineated as different species in the species delimitations. The mean divergence time between <i>T. kuroiwae</i> in the Ryukyu Islands and its congener, <i>T. brevispinis</i> and <i>T. obscurus</i> in the Japan Archipelago was dated back to 1.53 mya and close to the formation of the Tokara Gap (~1.5 mya), which might be a barrier driving divergence of the three species. However, as many <i>Tridentiger</i> species show different salinity and habitat preferences, ecological factors might also play important roles in evolution of the genus <i>Tridentiger</i>.