Evolution and disappearance of sympatric Coregonus albula ina changing environment—A case study of the only remainingpopulation pair in Sweden

• During the past 50 years, Fennoscandian populations of spring‐spawning Baltic cisco(Coregonus albula), sympatric to common autumn‐spawners, have declined or disappeared;for example, three out of four known spring‐spawning populations in Swedenare regarded as extinct. Over the same period, the climate has changed and populationshave been subject to other anthropogenic stressors. We compared historic(1960s) and recent (1990–000s) morphological data from the still‐existent sympatriccisco populations in Lake Fegen, Sweden. Phenotypic changes were found forspring‐spawners making them more similar to the sympatric autumn‐spawners thathad remained virtually unchanged. Based on results for other salmoniform fishes,a phenotypically plastic response to increased temperature during early developmentappears unlikely. The recent material was also analyzed with microsatellitemarkers; long‐term effective population size in spring‐spawners was estimated tobe about 20 times lower than autumn‐spawners, with signs of long‐term gene flowin both directions and a recent genetic bottleneck in spring‐spawners. We suggestthe change toward a less distinct phenotype in spring‐spawners to reflect a recentincrease in gene flow from autumn‐spawners. Time since divergence was estimatedto onlyc. 1,900 years (95% CI: 400–5,900), but still the Fegen populations representthe most morphologically and genetically distinct sympatric populations studied.Consequently, we hypothesize that less distinct population pairs can be evenyounger and that spring‐spawning may have repeatedly evolved and disappeared inseveral lakes since the end of the last glaciation, concurrent with changed environmentalconditions.

Ämnesord

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

Nyckelord

climate

Coregonus

microevolution

microsatellites

morphology

Livets mångfald

Diversity of life

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