DEVELOPMENTAL STABILITY OF SKULL MORPHOLOGY IN EUROPEAN BISON-BISON BONASUS

We compared developmental stability and total phenotypic diversity of 25 skull characters in three populations of European bison Bison bonas us (Linnaeus, 1758). Developmental stability was measured by fluctuati ng asymmetry, which was estimated by the variance of the left-right (l -r) and scaled (l-r)/(l+r) differences between the left (l) and right (r) sides of the skull. Mean number of asymmetrical characters per ind ividual was used as an integrated index of developmental stability. To tal phenotypic variability was examined by variance of (l+r) for the s ame characters. Greater developmental instability and total phenotypic diversity were found in bison from Pszczyna Reserve and Bialowieza Pr imeval Forest, as compared with those from Okskii Reserve. This indica tes the gradual deterioration of developmental stability in the follow ing sequence of the studied populations: Okskii Reserve, Bialowieza Pr imeval Forest, Pszczyna Reserve. In the Bialowieza population, deterio ration of developmental stability could be detected, even though commo nly used fitness measures showed no response. In the Pszczyna populati on, more serious developmental stability disturbance was accompanied b y decreased viability, an expression of inbreeding depression. Two sam ples taken from the Bialowieza population at different times showed si milar levels of developmental stability, which indicates the reliabili ty of fluctuating asymmetry. These results suggest developmental stabi lity to be an essential characteristic for monitoring populations and especially for revealing the initial response to stress.