Shell-shape variation along the latitudinal range of the Chilean blue mussel Mytilus chilensis (Hupe 1854)

Shell-shape variation in the Chilean blue mussel Mytilus chilensis was examined in eight populations covering the totality of its distribution range, which represents over 1800 km of latitudinal gradient in the southeastern Pacific. The shell outline shapes were assessed using elliptic Fourier analysis followed by canonical variates analysis. Fourier coefficients showed a highly significant morphological variation between the populations studied. Canonical variates analysis showed a visual association of the First canonical with convexity of ventral edge and umbo shape, while the second axis was associated with shell elongation. Previously described genetic patterns were marginally congruent with our morphometric pattern, though geographic distance had a stronger effect on morphology. Shape change (elongation) was correlated with latitudinal clinal variation. The morphometrical analysis proved to be an important tool for evaluating the components of shell-shape variation in mussels and to document association patterns with geographical and ecological variables. Such patterns are useful to establish a wide field of work, including sexing, stock recognition, traceability studies and productive management in general.