Morphometric differentiation in populations of the Central European sculpin <i>Cottus gobio</i> L., a fish with deeply divergent genetic lineages

Abstract

The morphological differentiation between four population collectives of the Central European sculpin Cottus gobio from southwestern Germany and adjacent France (the contact region of the Rhine, Danube, and Rhône drainage basins) was evaluated using multivariate analysis of 34 morphometric and 3 meristic characters. Body shape separated Neckarian and Danubian sculpins, Rhenish stocks taking a somewhat intermediate position. These morphological differences between populations from various drainage basins were slighter than the deeper allozyme differentiation observed in a previous study. However, both allozymes and morphometry indicated the same population groupings. It is concluded that C. gobio displays an accelerated rate of allozyme evolution, or that stabilizing selection conserves its phenotype despite ongoing evolution at the protein level. The morphological data do not support the distinction of species in the area of the Rhine/Danube watershed.