Evol Ecol Res 14: 487-502 (2012)     Full PDF if your library subscribes.

Does water depth or diet divergence predict progress towards ecological speciation in whitefish radiations?

Travis Ingram¹, Alan G. Hudson^2,3,4, Pascal Vonlanthen^2,3 and Ole Seehausen^2,3

¹Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA,  ²Division of Aquatic Ecology and Macroevolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland,  ³Department of Fish Ecology and Evolution, Eawag Centre for Ecology, Evolution and Biogeochemistry, Kastanienbaum, Switzerland and  ⁴Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain

Correspondence: T. Ingram, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
e-mail: ingram@fas.harvard.edu

ABSTRACT

Question: Is the extent of genetic divergence between sympatric whitefish ecotypes – a proxy for progress towards speciation – related to the extent of ecological divergence in spawning depth or diet?

Study system: Whitefish (Coregonus spp.) that have diversified into two or more sympatric ecotypes in subalpine Swiss lakes. Sympatric ecotypes vary in the extent of reproductive isolation.

Analytical methods: We measured the degree of spawning depth differentiation based on the depth-at-capture of different ecotypes. We estimated diet differentiation between ecotypes as Mahalanobis distances from stable isotopes. We compared each of these to genetic differentiation measured from AFLP data, using modified correlation tests and phylogenetically independent contrasts to account for non-independence of comparisons in lakes with more than two ecotypes.

Results: We found that the magnitude of divergence in spawning depth was generally – albeit only marginally significantly – associated with the extent of genetic divergence between sympatric ecotypes. This effect was clearly stronger than the effect of diet divergence, which was not associated with genetic differentiation. Furthermore, there was no evidence for an interactive effect of depth and diet divergence on progress towards speciation.

Keywords: AFLP, Coregonus spp., parapatric speciation, stable isotope analysis, sympatric speciation.

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