Craniometrical variability and developmental stability. Two useful tools for assessing the population viability of Eurasian otter (Lutra lutra) populations in Europe.

Morphometrical univariate analyses of otter skulls collected over the past hundred years in European countries from presumed healthy populations were compared with skulls from presumed endangered populations. The average degr ee of sexual dimorphism of the European populations was found to be directl y correlated to the skull size of the male otters. Fluctuating asymmetry (F A) in metric skull traits was analysed as an estimator of developmental sta bility. There was evidence for increased FA in different traits over time i n some of the presumed endangered populations, and for a reduction in size of skull traits. In contrast, the healthy populations did not show any sign ificant changes in the same traits during the same period. The reduced sexu al dimorphism of the endangered populations is suggested to be a product of relaxed sexual selection and deteriorated habitat conditions. Environmenta l and genetic forces that may have shaped these patterns are discussed. (C) 2000 The Linnean Society of London.