The Arctic char (Salvelinus alpinus) “complex” in North America revisited Eric B. Taylor Hydrobiologia The International Journal of Aquatic Sciences ISSN 0018-8158 Hydrobiologia DOI 10.1007/s10750-015-2613-6 1 23 Author's personal copy Hydrobiologia DOI 10.1007/s10750-015-2613-6 CHARR II Review Paper The Arctic char (Salvelinus alpinus) ‘‘complex’’ in North America revisited Eric B. Taylor Received: 1 July 2015 / Revised: 16 November 2015 / Accepted: 5 December 2015 Ó Springer International Publishing Switzerland 2015 Abstract The Arctic char (Salvelinus alpinus) law. This research has significantly revised what species ‘‘complex’’ has fascinated biologists for constitutes the S. alpinus species ‘‘complex’’, provided decades particularly with respect to how many species insights into the ecology and genetics of co-existence, there are and their geographic distributions. I review and promoted conservation assessment that better recent research on the species complex, focussing on represents biodiversity within Salvelinus. A geograph- biodiversity within northwestern North America, ically and genetically comprehensive analysis of which indicates (i) what was once considered a single relationships among putative taxa of Pan-Pacific taxon consists of three taxa: S. alpinus (Arctic char), S. Salvelinus is still required to better quantify the malma (Dolly Varden), and S. confluentus (bull trout), number of taxa and their origins. (ii) morphological and genetic data indicate that S. alpinus and S. malma, and S. malma and S. confluentus Keywords Dolly Varden Á Arctic char Á Bull trout Á exist as distinct biological species in sympatry, (iii) Geographic distribution Á Taxonomy Á Conservation sympatric forms of S. alpinus exist in Alaska as in other areas of the Holarctic, (iv) Dolly Varden comprises two well-differentiated subspecies, S. m. malma and S. m. lordi, in the eastern Pacific and the Introduction northwestern Canadian Arctic that meet at a contact zone on the southern edge of the Alaska Peninsula, and In 1961, McPhail summarized the taxonomic com- (v) Dolly Varden and bull trout consist of several plexity of northwestern North America chars (Salveli- population assemblages that have legal status as nus) which included an array of morphological types distinct conservation units under US and Canadian within the Arctic char (Salvelinus alpinus) ‘‘complex’’ and he stated that it consisted of an ‘‘undetermined number of species’’. In particular, McPhail’s (1961) Guest editors: M. Power, R. Knudsen, C. Adams, M. J. Hansen, study strove to understand the systematic status of J. B. Dempson, M. Jobling & M. Ferguson / Advances in Charr Dolly Varden char (S. malma) as it related to one or Ecology and Evolution more other taxa within S. alpinus, yet it was even more E. B. Taylor (&) complicated than he envisioned. The immense phe- Department of Zoology, Biodiversity Research Centre and notypic complexity and its implications for systemat- Beaty Biodiversity Museum, University of British ics and taxonomy within the Arctic char group are Columbia, 6270 University Ave., Vancouver, BC V6T 1Z4, Canada intriguing (Klemetsen, 2013), but they are also part of e-mail: [email protected] a more general phenomenon of ‘‘species complexes’’ 123 Author's personal copy Hydrobiologia in several north temperate fishes (McPhail, 1966; McPhail (1961) concluded that one form resembled Hagen & McPhail, 1970; Behnke, 1972; Taylor, Arctic char and the other resembled Dolly Varden. 1999). McPhail’s (1961) analysis, therefore, was the first Since McPhail’s (1961) study, considerable ‘‘acid test’’ of the distinct biological species status of research has been conducted on the evolutionary the two chars using morphological data (Avise, relationships between and within S. alpinus and S. 1994)—they existed as discrete units in sympatry malma that have led to some clarification of the (see also DeLacy & Morton, 1943). A few samples taxonomic status, composition, and relationships from Hansen Creek in Lake Aleknagik (Bristol Bay), within the original S. alpinus complex, particularly however, did not fall neatly into either Arctic char or on what forms are outside, but related to, the S. alpinus Dolly Varden. McPhail (1961) suggested that these complex sensu stricto. Many of the studies, however, individuals might represent interspecific hybrids, have also raised new questions. In this brief review, I although he concluded that these fish were ‘‘a form’’ summarize the major results and identify new ques- of S. malma rather than hybrids. Further, Gharrett et al. tions. This review focusses on northwestern North (1991) conducted an allozyme study of sympatric America and principally on distinctions and relation- Arctic char and Dolly Varden in the Karluk River ships among named taxa and not a second aspect of system and demonstrated significant, and sometimes complexity within the S. alpinus complex, i.e. that of striking, differences between the two char at several myriad forms of sympatric populations some of which loci strongly supporting their status as distinct biolog- have been given taxonomic designations. An exten- ical species. sive literature already exists for char in eastern North The work of McPhail (1961) was followed up by a America and Eurasia in terms of taxonomy, phylo- series of investigations (e.g. McCart, 1980; Morrow, geography, and sympatric populations within S. alpi- 1980; Reist et al., 1997) that better defined the nus senu lato (e.g. Nordeng, 1983; Jonsson & Jonsson, geographic distributions of the two chars, particularly 1991; Savvaitova, 1995; Kottelat & Freyhof, 2007; with respect to the ‘‘Bering Sea-Western Arctic’’ form Klemetsen, 2013; Reist et al., 2013). of S. alpinus proposed by McPhail (1961). Taken together, these works, and especially that of Reist et al. (1997), established the currently accepted distribu- Species identity tions of S. malma and S. alpinus in Alaska and the Canadian Arctic. The distribution of S. malma In McPhail’s (1961) study, the morphological data led includes riverine and anadromous char west of the him to conclude that there were at least two species of Mackenzie River to and including the Gulf of Alaska, char within the Arctic char group (Dolly Varden and southeast Alaska, British Columbia and northwest Arctic char), each with three morphological types that Washington. The distribution of S. alpinus includes were strongly patterned geographically. Within S. lacustrine char from the Gulf of Alaska north to and malma, there was a form found south of the Alaska east of the Mackenzie River and anadromous and Peninsula (‘‘southern Dolly Varden’’), a form found lacustrine char from east of the Mackenzie River north of the Alaska Peninsula and eastward to the (Reist et al., 1997). These data refuted the idea that Mackenzie River (‘‘northern Dolly Varden’’), and there was a Bering Sea-western Arctic form of S. possibly an interior Alaskan form. Within S. alpinus, alpinus (McPhail, 1961; McCart, 1980) and these fish there was a Bering Sea-western Arctic form, an eastern were demonstrated to be Dolly Varden (Reist et al., form distributed east of the Mackenzie River, and a 1997). Bristol Bay-Gulf of Alaska form. Both the species and Finally, several morphological, ecological, and forms within species were defined largely by differ- genetic studies of interior forms of ‘‘Dolly Varden’’ ences in numbers of gill rakers, vertebrae, and pyloric sensu McPhail (1961) have illustrated that most caeca (McPhail, 1961; Reist et al., 1997). McPhail populations found in inland areas of western and (1961) also studied morphology and char within a few some eastern tributaries of the Mackenzie River, east Alaskan lakes and demonstrated that in all areas there of the Coastal-Cascade mountain crests, and east to the were two discrete forms of char living in sympatry. In headwaters of the Saskatchewan and Missouri rivers in comparison with reference samples from other areas, western North America are bull trout (S. confluentus) 123 Author's personal copy Hydrobiologia and not Dolly Varden (Cavender, 1978; Haas & tributaries of the western Pacific basin (e.g. Oleinik McPhail, 1991; Baxter et al., 1997; Redenbach & et al., 2007; Osinov et al., 2015; Senchukova et al., Taylor, 2003; Mochnacz et al., 2013). A few Dolly 2015). For instance, consider the three enigmatic char Varden populations, however, are found east of the of Lake El’gygytgyn in eastern Siberia. Here, the long- continental divide in the interior of Yukon (e.g. Peel finned char (Salvethymus svetovidovi), the small- River basin) and Northwest Territories (Reist et al., mouth char (Salvelinus elgyticus), and Boganida char 2002) as well as in the Peace River basin in British (S. boganidae) are all strikingly morphologically and Columbia as a result of historical watershed exchanges genetically distinct from one another in sympatry. (Baxter et al., 1997). Despite their distinct taxonomic designations, includ- In summary, the study of char over the last 54 years ing one form constituting a monotypic genus, some has peeled away skins of the onion-like S. alpinus genetic data suggest that they cluster tightly with ‘‘complex’’. There are, at least, three species in members of S. malma/S. alpinus from other regions of western North America (Fig. 1): Arctic char, Dolly the North Pacific basin (Osinov et al., 2015). A Varden, and bull trout (in addition to the native geographically and genetically comprehensive Pan- populations of lake trout, S. namaycush, which have Pacific analysis of the phylogenetic affinities of all never been considered part of the S. alpinus complex). Salvelinus and closely related forms (e.g. Salvethy- The taxonomic situation in western North America mus) is required to better understand the level of contrasts markedly with myriad forms, many of diversity in these chars, i.e. if some taxa should be uncertain taxonomic status, that occur in many synonymized and perhaps new forms recognized. Fig. 1 Current approximate distributions of Arctic char Taylor & May-McNally, 2015 and Fig. 4). Black dashes (Salvelinus alpinus: brown shading), Dolly Varden (S. malma: associated with Arctic char distribution indicate uncertain red hatched shading), and bull trout (S.