Morphological and Genetic Diversity of Amur Graylings ( Thymallus , Thymallidae)

Abstract

Four forms of graylings are found in the Amur basin, designated conventionally as: Upper-Amur, yellow-spotted, Lower-Amur, and large-scale. The Upper-Amur form is distributed from the upper reaches of the Ingoda and Onon up to the inflow to the Amur of the Bureya River, where its sympatry was observed with the Lower-Amur and large-scale forms. The latter also live together in tributaries of the Amur and in some rivers flowing into the Sea of Japan and the Tatar Strait. The results of the multivariate analysis of morphometric and meristic characters, sequences of mitochondrial DNA, and of body coloration and of patterns of the dorsal fin indicate that all of the aforementioned forms are isolated reproductively. The graylings from the Amur are rep- resented by two phylogenetic lines, the Upper-Amur, yellow-spotted, and Lower-Amur form belonging to the first line and the large-scaled form—to the second line. A high divergence level of the large-scaled form, accord- ing to analysis of mitochondrial DNA, is indicated not only for the Amur groups but also for other Siberian graylings. Of all discerned forms only two, the Upper-Amur and yellow-spotted ones, may be attributed to the previously described species by Dybowski Thymallus grubii. The Lower-Amur form is also an independent species. The taxonomic status of the large-scale form may be defined by further investigations. The obtained data indicate the urgency of revision of the genus Thymallus.