FLUCTUATING ASYMMETRY IN TAMARIN (SAGUINUS) CRANIAL MORPHOLOGY - INTRASPECIFIC AND INTERSPECIFIC COMPARISONS BETWEEN TAXA WITH VARYING LEVELS OF GENETIC HETEROZYGOSITY

Fluctuating asymmetry has been proposed as a measure of developmental homeostasis and an indicator of populations under stress. However, con troversy surrounds not only the validity of an association between flu ctuating asymmetry and levels of protein heterozygosity, but also whet her fluctuating asymmetry can be used to identify populations under ge netic and environmental stress, The relationship between levels of het erozygosity and developmental homeostasis is considered by comparing l evels of cranial fluctuating asymmetry in three tamarin samples with c ontrasting levels of heterozygosity: (1) low heterozygosity cotton-top tamarins (N = 324), (2) presumably normally heterozygous Illiger's sa ddle-back tamarins (N = 208), and (3) relatively highly heterozygous h ybrids between saddle-back tamarin subspecies (N = 31). All specimens originated at the Oak Ridge Associated Universities' Marmoset Research Center. A nested ANOVA design was used to separate out variation due to individual differences, side-to-side differences (fluctuating asymm etry), and measurement error. We found statistically significant level s of fluctuating asymmetry in nearly all of the traits surveyed and a negative correlation between levels of fluctuating asymmetry and genet ic heterozygosity. Efforts to use fluctuating asymmetry to identify po pulations endangered by reduced genetic variability and/or under stres s may be inhibited by small sample sizes, neglect of repeated measures , and lack of appropriate reference populations.