Horn antisymmetry in a local goat population
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Fluctuating asymmetry (FA) refers to small random deviations from perfect bilateral symmetry. Directional asymmetry (DA) is defined as population-level deviations from bilateral symmetry that are unimodal and significantly different from symmetry. Lastly, antisymmetry (AS) is a pattern of bilateral variation in which differences exist between sides, but the side that is larger varies randomly among individuals. FA reflects the ability of individuals to undergo stable development, so it may provide a potential measure of individual quality. FA is not likely to be adaptive but both DA and AS are developmentally controlled and are therefore likely to have adaptive significance. Twenty-seven adult females belonging to the Catalan goat population (NE Spain) were studied to assess horn perfect symmetries (in total length and base circumference) as indicators of their fitness. Symmetry was tested by means of Wilcoxon signed test and dispersion values. Platykurtic distributions and plotting the cumulative frequency was used to assess DA and AS. For horn length, but not for horn circumference, AS was revealed. Although AS has been considered to be developmentally controlled and possibly adaptive, the specific processes producing this pattern in Catalan goat horn remain a matter of discussion.