Crater lake cichlids individually specialize along the benthic–limnetic axis
Article first published online: 7 MAR 2014
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Ecology and Evolution
Volume 4, Issue 7, pages 1127–1139, April 2014
How to Cite
Ecology and Evolution 2014; 4(7):1127–1139
- Issue published online: 7 APR 2014
- Article first published online: 7 MAR 2014
- Manuscript Accepted: 7 FEB 2014
- Manuscript Revised: 4 FEB 2014
- Manuscript Received: 4 NOV 2013
- Deutsche Forschungsgemeinschaft
- Alexander von Humboldt fellowship
- European Research Council (ERC). Grant Number: 293700
- Deutsche Cichliden Gesellschaft
- Benthic–limnetic axis;
- divergent selection;
- ecological opportunity;
- individual specialization;
- parallel evolution;
- phenotype-diet correlation
A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have suggested that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan crater lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche suggested that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the crater lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young crater lake species encompasses the limnetic- as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence.