Water Transparency Drives Intra-Population Divergence in Eurasian Perch (Perca fluviatilis)

Pia Bartels,Peter Eklöv,Philipp E Hirsch,Richard Svanbäck,William J Etges

doi:10.1371/journal.pone.0043641

Abstract

Trait combinations that lead to a higher efficiency in resource utilization are important drivers of divergent natural selection and adaptive radiation. However, variation in environmental features might constrain foraging in complex ways and therefore impede the exploitation of critical resources. We tested the effect of water transparency on intra-population divergence in morphology of Eurasian perch (Perca fluviatilis) across seven lakes in central Sweden. Morphological divergence between near-shore littoral and open-water pelagic perch substantially increased with increasing water transparency. Reliance on littoral resources increased strongly with increasing water transparency in littoral populations, whereas littoral reliance was not affected by water transparency in pelagic populations. Despite the similar reliance on pelagic resources in pelagic populations along the water transparency gradient, the utilization of particular pelagic prey items differed with variation in water transparency in pelagic populations. Pelagic perch utilized cladocerans in lakes with high water transparency and copepods in lakes with low water transparency. We suggest that under impaired visual conditions low utilization of littoral resources by littoral perch and utilization of evasive copepods by pelagic perch may lead to changes in morphology. Our findings indicate that visual conditions can affect population divergence in predator populations through their effects on resource utilization.

Highlights

Differences in habitat and resource use have long been viewed as a major cause of phenotypic divergence within and between species
In particular we investigated two hypotheses and predicted that: i) intra-population divergence would be stronger at high water transparency due to the availability of alternate habitats and resources, and ii) intra-population divergence would be low in lakes with low water transparency due to higher similarity of resource use by pelagic and littoral perch
Fish communities in all lakes were dominated by roach (Rutilus rutilus) and perch (Table S2)

Summary

Introduction

Differences in habitat and resource use have long been viewed as a major cause of phenotypic divergence within and between species. This is because different environments require adaptations of behavioral, morphological, or life history traits [1] which increase the individuals fitness and may lead to adaptive radiation and ecological speciation [2]. A decrease in water transparency, regardless of the cause (i.e. turbidity or DOM) can affect aquatic organisms that depend on vision for foraging, mating, or intra-specific communication [11,12,13]. Alterations in resource use or in foraging behavior due to decreasing water transparency have previously been studied their effects on population divergence are currently not known

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Conclusion