Thymallus tugarinae

Taylor Elsa Froufe, Steven J. Weiss Duarte V. Gonçalves Giulia Secci-Petretto Gernot K. Englmaier André Gomes-Dos-Santos Gael P. J. Denys Henri Persat Alexander Antonov Christoph Hahn Eric B., 2021, Global systematic diversity, range distributions, conservation and taxonomic assessments of graylings (Teleostei: Salmonidae; Thymallus spp.), Organisms Diversity & Evolution (New York, N. Y.) 21 (1), pp. 25-42 : 35-36

Thymallus tugarinae — Lower Amur grayling

Occurs in the middle to lower Amur River drainage and several coastal draining rivers including northwestern Sakhalin Island ( Fig. 1 ). Highly divergent from its sister clade containing T. grubii (4.1%) and T. flavomaculatus (4.2%). Easily distinguished from sympatric T. flavomaculatus using meristic or morphological characters ( Knizhin et al. 2007); reciprocally monophyletic with other Amur graylings (Fig. 2) ( Froufe et al. 2003b, 2005); reproductive isolation support- ed ( Froufe et al. 2003b). Shows significant phylogeographic structure across its range ( Froufe et al. 2003b).

Taxonomic validity

A species reproductively isolated and easily distinguished from the sympatric T. flavomaculatus (see T. flavomaculatus below).

Conservation remarks

Area of occupancy exceeds 2000 sq. km. Suggested Global Status: Least Concern.

Thymallus flavomaculatus — Yellow-spotted grayling

Occurs in some coastal rivers draining into the seas of Japan and Okhotsk, as well as some lower Amur River tributaries ( Fig. 1 ); overlaps considerably with T. tugarinae ( Froufe et al. 2003b; Antonov and Knizhin 2011). Easily distinguished from T. grubii and sympatric T. tugarinae based on a characteristic yellow-orange spot located in the posterior area of the dorsal fin ( Knizhin et al. 2006a).

Taxonomic validity

The taxon was originally described as a subspecies of T. grubii , widely distributed in the Amur River drainage. Whether or not the taxon is treated as a species or a subspecies is beyond the scope of this manuscript. In our analysis, T. flavomaculatus is paraphyletic (see additional comments below for T. grubii ).

Conservation remarks

Coastal populations are more threatened by anthropogenic changes and overfishing than interior populations. Some range fragmentation is present and the area of occupancy may be as little as 400 sq. km. Suggested Global Status: Near threatened.

Thymallus grubii — Amur grayling

A small-sized grayling, easily diagnosed based on body and dorsal-fin colouration; occurs throughout the middle to upper Amur River drainage ( Fig. 1 ). Significant phylogeographic structure is reported ( Froufe et al. 2003b; Knizhin et al. 2004; Weiss et al. 2020b). Occurs in sympatry with T. burejensis and T. baicalolenensis in the upper Bureya River, where reproductive isolation is strong but not complete ( Weiss et al. 2020b), and in sympatry with T. tugarinae in the lower Zeya River and Ingoda River, and with T. baicalolenensis in the upper Zeya River and upper Ingoda River ( Antonov and Mikheev 2016).

Taxonomic validity

A species diagnosable from all other grayling ( Weiss et al. 2020b). Could be also treated as the nominal species of a three-taxon aggregate, consisting of T. ( grubii ) grubii , T. ( grubii ) flavomaculatus and T. ( grubii ) yaluensis (see Article 6.2 in the International Commission on Zoological Nomenclature 1999) (see also Appendix I).

Conservation remarks

Occupies a relatively large range and several relatively pristine river systems. Suggested Global Status: Least Concern.

Thymallus burejensis —Bureya grayling

A robust-bodied grayling, endemic to the middle and upper reaches of the Bureya River. Occurs in sympatry in the upper Bureya River with T. baicalolenensis and T. grubii , and shows relatively strong (albeit not complete) reproductive isolation ( Weiss et al. 2020b). Mitogenomic distances range from 3.0 to over 4.9% between T. burejensis and all other congeners.

Taxonomic validity

A species displaying significant reproductive isolation with two other grayling taxa.

Conservation remarks

The Bureya River is over 700 km in length but the mid-tolower reaches have been heavily impacted by hydropower, eliminating or fragmenting portions of the specie’ s range. Currently, its area of occupation does not exceed 100 sq. km. Suggested Global Status: Endangered.

Figures

Fig. 1 Map showing the global distribution range of Thymallus species. Information on sampling sites and species is given in Table S1. Numbers in the map refer to known contact zones of the following species: 1 = T. arcticus s.l. and T. baicalensis in the lower Enisei River; 2 = T. arcticus s.l. and T. baicalolenensis in the lower Lena River; 3 = T. nikolskyi and T. baicalensis in tributaries of the upper Ob River; 4 = T. baicalolenensis and T. baicalensis in tributaries of Lake Baikal; 5 = T. grubii, T. tugarinae