Arctic charr (Salvelinus alpinus): a case study of the importance of understanding biodiversity and taxonomic issues in northern fishes

Abstract

Charrs, fishes of the genus Salvelinus (Salmonidae), comprise about 7–20+ species important in the ecosystems and fisheries of Arctic and sub-Arctic waters. Charrs vary by life-history type (anadromous vs. lacustrine), are noted for variability in morphology, colouration and feeding and habitat use across their range, and occur from temperate regions to the northernmost areas of land. Charr diversity is manifested as an often confusing array of taxonomic and functional diversity. Components of taxonomic diversity include unresolved species’ complexes, subspecies, glacial lineages and genetic stocks. Features associated with functional diversity include semi-distinct life history variants and differential habitat and feeding tactics resulting in distinctive growth forms. Complex periglacial histories, allopatric and sympatric diversification processes, founder effects, hybridisation and introgression have contributed to the observed variability and complexity. The categorisation of taxonomic and functional diversity and understanding their roles, drivers and vulnerabilities underpins conservation and management efforts for taxa and their ecosystems. In that context, Arctic charr is an excellent example of diversity and the many levels of difficulties associated with determining the significance of diversity. Despite recently increased scientific efforts, resolving the nature and importance of charr diversity remains both a challenge and a priority because rapid anthropogenically driven change, especially climate change, is altering ecosystems and biodiversity faster than diversity can be inventoried, its importance understood and protective measures developed.