Biodiversity of central alpine coregonus (salmoniformes): impact of one‐hundred years of management

Coregonus has been under intense management in the Central Alpine region of Europe for more than 100 yr. To assess how this management has affected local populations, extant patterns of genotypic and phenotypic diversity were examined within a taxonomic framework to identify indigenous and introduced populations, and to provide a perspective on future management based on true conservation units. Thirty‐three Coregonus populations from 17 selected Central Alpine lakes were classified as indigenous, introduced, or uncertain (i.e., status or origin unknown). Using genetic data across six microsatellite DNA loci, individuals of the 19 indigenous populations could be correctly allocated to population with 71% probability in a nonparametric discriminant analysis. The same individuals could be allocated to population with 69% probability using five meristic counts, and but 44% probability using four fin‐pigmentation characteristics. Discriminating ability was enhanced to 91% when both meristic and color data were coalesced, and composite use of genetic and phenotypic data provided an average discrimination probability of 79%. Capabilities of the various data sets decreased when applied separately to allocate specimens according to either lake (n = 8) or lake‐aggregate (n = 5). Genetic data were then statistically contrasted against four taxonomic hierarchies: Kottelatt's species arrangement, and Steinmann's depiction of “ecotype,” “natio,” and a combination of the two. Genetic data were statistically congruent with Kottelat's depiction of species, and with Steinmann's arrangement of populations into natio (or regions). Results support arguments that indigenous populations of Central Alpine Coregonus are distinct, with closest relations within lakes (or lake aggregates). Their evolutionary origin is best described using a species‐flock model. Genetic data for 19 indigenous populations were combined with those for 14 populations either introduced or of unknown provenance. Pairwise comparisons of allele and genotype frequencies demonstrated significant genetic differences among populations, supporting uniqueness of rare forms, such as “alpenrheinfelchen” of Lake Konstanz or “winterbrienzlig” of Lake Brienz, but also revealed genetic divergence of introduced populations from their alleged source. Introduced populations clustered within the group containing their population of origin but did not associate directly with their source, thus indicating post‐introduction genetic divergence. These findings were most remarkable for “balchen” of Lake Ägeri and “palee” from Lake Geneve (stocked from lakes Zug and Geneve, respectively). Also, “sempacherbalchen” of Lake Sempach was significantly distinct from all other populations, even though it was supposedly stocked “from every lake and into every lake.” It also clustered with populations in geographic proximity, suggesting that it may still retain historic endemicity. Finally, “lavarello” and “nuova forma” from Lake Maggiore did not group as expected with forms from Lake Konstanz or lakes Neuchâtel/Bienne, but instead with those from Lake Zug. Nonparametric discriminant analyses over 32 populations, again employing genotypic and phenotypic data, confirmed divergence of introduced populations and clarified status for populations of uncertain origin. Results of analyses also confirmed that historic signatures still persist in extant populations. However, several examples also demonstrate that indiscriminant and undocumented stocking in the Central Alpine region during the last 100 yr has simply added to the confusion already extant from naturally occurring cryptic and sibling species within these lakes. Thus, until species descriptions are forthcoming for all forms, the Central Alpine Coregonus lineage should be viewed as an “evolutionarily significant unit” (ESU), and each population a specific “management unit” (MU) within that lineage.