Abstract
BackgroundThe diversity and phylogeny of whitefish of the genus Coregonus is complex, and includes many endemic species of high conservation concern. However, because of commercial importance of whitefish fisheries, stockings and translocations have occurred repeatedly, which challenges the identification of local populations as conservation units. This study analyses the phylogenetic relationships of 15 contemporary and two historical populations of lake-resident and anadromous whitefish (Coregonus spp.) from the southern Baltic and North Sea basins. We elucidated the complex history of Lake Schaal (northern Germany) whitefish, for which a local tale suggests that the devil threw whitefish from the Central European Lake Constance into this lake. Studies from the early twentieth century indeed suggested numerous stocking events for Lake Schaal from Lake Constance, from Estonian/Russian Lake Peipsi and from the anadromous whitefish of the Baltic Sea.ResultsAnalyses of 13 microsatellite markers showed that Lake Constance whitefish are unrelated to any northern Germany whitefish population, including the contemporary whitefish population from Lake Schaal. Comparison with four historical specimens further showed that the native Lake Schaal whitefish (C. holsatus) vanished from the lake, but has survived as a non-native population in the north German Lake Drewitz. The whitefish currently occurring in Lake Schaal and three adjacent lakes are identified as C. maraenoides, introduced from Lake Peipsi. The contemporary anadromous whitefish populations from the Baltic (German and Finnish coast) and the German River Treene (North Sea basin, stocked from Danish River Vida) grouped together, but showed significant genetic differentiation. The 14 historical specimens of C. oxyrinchus from Rivers Rhine and Schelde were assigned to several contemporary whitefish populations, but among them only one specimen was assigned to the contemporary River Treene population. Therefore, we do not support the view that the whitefish from River Vida/Treene are identical with the historical C. oxyrinchus.ConclusionsOur study demonstrates that lake and anadromous whitefish in the Baltic and North Sea basins reflect a complex phylogeography, which is further blurred by the effects of repeated stocking and translocations. To identify conservation units, the genetic identity of each population has to be scrutinized.
Highlights
The diversity and phylogeny of whitefish of the genus Coregonus is complex, and includes many endemic species of high conservation concern
Genetic structure within populations Sample sizes were different between populations
Allelic richness AR, the mean number of alleles per locus and population adjusted to the minimum N = 7, varied little among populations (Table 1)
Summary
The diversity and phylogeny of whitefish of the genus Coregonus is complex, and includes many endemic species of high conservation concern. Studies from the early twentieth century suggested numerous stocking events for Lake Schaal from Lake Constance, from Estonian/Russian Lake Peipsi and from the anadromous whitefish of the Baltic Sea. Whitefish of the genus Coregonus represent a large group of medium to large-sized resident or migratory freshwater fishes. The number of gill rakers may undergo rapid modifications when environmental conditions change [15], and their reliability as taxonomic character has to be assessed for each population with great care Due to their high commercial value, stockings from multiple origins even over large spatial distances have been reported for Coregonus since the fourteenth century [16,17,18], but details are usually poorly documented and stocking history is rarely retraceable. Current populations may comprise a mix of native and introduced genotypes due to introgressive hybridization [19]
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