Genetic and morphometric divergence in threespine stickleback in the Chignik catchment, Alaska
Article first published online: 18 DEC 2013
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Ecology and Evolution
Volume 4, Issue 2, pages 144–156, January 2014
How to Cite
Ecology and Evolution 2014; 4(2):144–156.
- Issue published online: 20 JAN 2014
- Article first published online: 18 DEC 2013
- Manuscript Accepted: 24 NOV 2013
- Manuscript Revised: 11 NOV 2013
- Manuscript Received: 6 NOV 2013
- Norwegian Research Council
- life-history polymorphism;
- phenotypic differentiation;
- population differentiation
Divergent selection pressures induced by different environmental conditions typically lead to variation in life history, behavior, and morphology. When populations are locally adapted to their current environment, selection may limit movement into novel sites, leading to neutral and adaptive genetic divergence in allopatric populations. Subsequently, divergence can be reinforced by development of pre- or postzygotic barriers to gene flow. The threespine stickleback, Gasterosteus aculeatus, is a primarily marine fish that has invaded freshwater repeatedly in postglacial times. After invasion, the established freshwater populations typically show rapid diversification of several traits as they become reproductively isolated from their ancestral marine population. In this study, we examine the genetic and morphometric differentiation between sticklebacks living in an open system comprising a brackish water lagoon, two freshwater lakes, and connecting rivers. By applying a set of microsatellite markers, we disentangled the genetic relationship of the individuals across the diverse environments and identified two genetic populations: one associated with brackish and the other with the freshwater environments. The “brackish” sticklebacks were larger and had a different body shape than those in freshwater. However, we found evidence for upstream migration from the brackish lagoon into the freshwater environments, as fish that were genetically and morphometrically similar to the lagoon fish were found in all freshwater sampling sites. Regardless, few F1-hybrids were identified, and it therefore appears that some pre- and/or postzygotic barriers to gene flow rather than geographic distance are causing the divergence in this system.