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Morphological and trophic divergence of lake and stream minnows (Phoxinus phoxinus)
  • Kristin Scharnweber
Kristin Scharnweber
Uppsala Universitet
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Peer review status:ACCEPTED

26 Apr 2020Submitted to Ecology and Evolution
27 Apr 2020Assigned to Editor
27 Apr 2020Submission Checks Completed
29 Apr 2020Reviewer(s) Assigned
09 May 2020Review(s) Completed, Editorial Evaluation Pending
11 May 2020Editorial Decision: Revise Minor
01 Jun 20201st Revision Received
03 Jun 2020Review(s) Completed, Editorial Evaluation Pending
03 Jun 2020Assigned to Editor
03 Jun 2020Submission Checks Completed
05 Jun 2020Editorial Decision: Revise Minor
06 Jun 20202nd Revision Received
08 Jun 2020Review(s) Completed, Editorial Evaluation Pending
08 Jun 2020Submission Checks Completed
08 Jun 2020Assigned to Editor
10 Jun 2020Editorial Decision: Accept

Abstract

Phenotypic divergence in response to divergent natural selection between environments is a common phenomenon in species of freshwater fishes. Intraspecific differentiation is often pronounced between individual inhabiting lakes versus stream habitats. The different hydrodynamic regimes in the contrasting habitats may promote a variation of body shape, but this could be intertwined with morphological adaptions to a specific foraging mode. Herein, I studied the divergence pattern of the European minnow (Phoxinus phoxinus), a common freshwater fish that has paid little attention despite its large distribution. In many Scandinavian mountain lakes, they are considered as being invasive and were found to pose threats to the native fish populations due to dietary overlap. Minnows were recently found to show phenotypic adaptions in lake versus stream habitats, but the question remained if this divergence pattern is related to trophic niche partitioning. I therefore studied the patterns of minnow divergence in morphology (i.e. using geometric morphometrics) and trophic niches (i.e. using stomach content analyses) in the lake Ånnsjön and its tributaries to link the changes in body morphology to the feeding on specific resources. Lake minnows showed a strong reliance on zooplankton and a more streamlined body shape with an upward facing snout, whereas stream minnows fed on macroinvertebrates (larvae and adults) to a higher degree and had a deeper body with a snout that was pointed down. Correlations showed a significant positive relationship of the proportion of zooplankton in the gut and morphological features present in the lake minnows. The results of this study highlight the habitat-specific divergence pattern in morphology and resource use in this ubiquitous freshwater fish, which may promote contrasting inter-specific interactions in the respective food webs.