52 Journal of Ichthyology, Vol. 44, No. 1, 2004, pp. 52–69. Translated from Voprosy Ikhtiologii, Vol. 44, No. 1, 2004, pp. 59–76. Original Russian Text Copyright © 2004 by Knizhin, Weiss, Antonov, Froufe. English Translation Copyright © 2004 by MAIK “Nauka /Interperiodica” (Russia). Morphological heterogeneity of graylings (Thymal- lus) populating various parts of the Amur basin was repeatedly noted by many researchers. However, all dif- ferences were considered to be the consequences of environmental influence (Tugarina and Khramtsova, 1980, 1981; Zinovyev et al., 1983; Karasev, 1987; Kos- titsyn and Zinovyev, 1988). Antonov (1995, 1999, 2000, 2001) arrived at a conclusion on the sympatry in the Levaya Bureya River of three “reproductively iso- lated” forms. There is a viewpoint implying close rela- tionship of Th. grubii from the Amur 1 and the East– Siberian Th. arcticus pallasi (Svetovidov, 1936; Zinoviyev et al., 1983; Antonov, 1995; Makoedov and Korotaeva, 1999). In the list of freshwater fishes of Russia (Boguts- kaya and Naseka, 2002) for the Amur, in addition to 1 The Amur grayling was described for the first time by Dybowski (1869) as Th. grubii. Later, the taxonomic status and accordingly the name were changed by Berg (1916) into Th. arcticus grubei. We use the original name of the Amur grayling given by Dybowski. Th. grubii Dybowski, 1869, four forms of graylings are declared: Thymallus sp. 1 (the Lower Amur, Primor’e), Thymallus sp. 2 (the Lower Amur, Primor’e), Thymal- lus sp. 3 (the Upper Amur, Bureya), and Thymallus sp. 4 (“large-scale” form, the Upper Amur), without any information on their morphological differences. Two forms of graylings without species determination are indicated by Shed’ko (2001) as Thymallus sp. 1 and Thymallus sp. 2 within the family Salmonidae for rivers of Primor’e, however his comparative remarks are superficial. The systematic status of the Amur grayling T. grubii Dybowski as an independent species has already been repeatedly discussed (Svetovidov, 1936; Berg, 1948; Nikolsky, 1956; Pivnicka and Hensel, 1978; Tugarina and Khramtsova, 1980, 1981; Zinovyev et al., 1983; Skurikhina, 1984; Skurikhina et al., 1985; Karasev, 1987). In detail, the history of this problem is described by Tugarina and Khramtsova (1980). Commonly, dis- cussions were concerned with the status of this form. With consideration of the results of the DNA × DNA hybridization analysis it was supposed that the grayling Morphological and Genetic Diversity of Amur Graylings (Thymallus, Thymallidae) I. B. Knizhin*, S. J. Weiss**, A. L. Antonov***, and E. Froufe**** * Irkutsk State University, ul. K. Marksa 1, Irkutsk, 664003 Russia e-mail: knizhin@home.isu.ru ** Institute of Zoology, Karl-Franzens University, Universitatsplatz 2, A-8010 Graz, Austria e-mail: steven.weiss@uni-graz.at *** Institute of Water and Ecological Problems, Far East Division, Russian Academy of Sciences, ul. Kim-Yu–Chen 65, Khabarovsk, 680000 Russia e-mail: Antonov@ivep.khv.ru **** Centro Estudios Ciencia Animal, Unidade de Genetica Animal e Conservacao, CECA-ICETA, R. Monte-Crasto, 4485-661, Vairao, Portugal e-mail: elsafrouf@mail.icav.up.pt Received October 22, 2002 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.