Phenotype-environment correlations in a putative whitefish adaptive radiation

Authors

  • Chris Harrod,

    Corresponding author
    1. Departments of Physiological Ecology & Evolutionary Genetics, Max Planck Institute for Limnology, D-24302 Plön, Germany
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    • Present address: Queen’s University Belfast, School of Biological Sciences, Belfast, BT9 7BL, UK.

  • Jennie Mallela,

    1. Departments of Physiological Ecology & Evolutionary Genetics, Max Planck Institute for Limnology, D-24302 Plön, Germany
    2. The Centre of Excellence for Coral Reef Studies and The Research School of Earth Sciences, The Australian National University, Canberra 0200, Australia
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  • Kimmo K. Kahilainen

    1. Department of Biological and Environmental Sciences, P.O. Box 65, FI-00014 University of Helsinki, Finland
    2. Kilpisjärvi Biological Station, University of Helsinki, Käsivarrentie 14622, FI-99490 Kilpisjärvi, Finland
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Correspondence author. E-mail: c.harrod@qub.ac.uk

Summary

1. The adaptive radiation of fishes into benthic (littoral) and pelagic (lentic) morphs in post-glacial lakes has become an important model system for speciation. Although these systems are well studied, there is little evidence of the existence of morphs that have diverged to utilize resources in the remaining principal lake habitat, the profundal zone.

2. Here, we tested phenotype-environment correlations of three whitefish (Coregonus lavaretus) morphs that have radiated into littoral, pelagic and profundal niches in northern Scandinavian lakes. We hypothesized that morphs in such trimorphic systems would have a morphology adapted to one of the principal lake habitats (littoral, pelagic or profundal niches). Most whitefish populations in the study area are formed by a single (monomorphic) whitefish morph, and we further hypothesized that these populations should display intermediate morphotypes and niche utilization. We used a combination of traditional (stomach content, habitat use, gill raker counts) and more recently developed (stable isotopes, geometric morphometrics) techniques to evaluate phenotype-environment correlations in two lakes with trimorphic and two lakes with monomorphic whitefish.

3. Distinct phenotype-environment correlations were evident for each principal niche in whitefish morphs inhabiting trimorphic lakes. Monomorphic whitefish exploited multiple habitats, had intermediate morphology, displayed increased variance in gillraker-counts, and relied significantly on zooplankton, most likely due to relaxed resource competition.

4. We suggest that the ecological processes acting in the trimorphic lakes are similar to each other, and are driving the adaptive evolution of whitefish morphs, possibly leading to the formation of new species.

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