Fluctuating asymmetry and canalization: An appraisal based on a-b ridge counts among Indian populations with diverse backgrounds

The relationship between fluctuating asymmetry, measured as the absolute di fference between the right and left a-b ridge counts, and total a-b (R + L) ridge count was studied in an assortment of Indian population samples repr esenting a wide spectrum of socioeconomic and occupational backgrounds. The y included marine fishermen, inland and estuarine fishermen as well as migr ants and their parental counterparts, tribes, and castes of different hiera rchy- lower, middle, and upper. The samples together numbered a total of 3, 239 subjects, 2,240 males and 999 females. The results failed to support Ja ntz and Webb's (1980) hypothesis of a quadratic relationship between fluctu ating asymmetry of a-b ridge count and its phenotypic value. Only 3 of 22 s amples (about 13%) showed a significant fit with a reasonable degree of con sistency over a set of independent random subsamples; even initially only 7 of 22 (about 30%) samples showed a significant fit, or nearly so. Suppleme ntary evidence drawn from these populations with reference to the relations hip between fluctuating asymmetry and heterozygosity levels and inbreeding coefficients was also consistent with the interference that fluctuating asy mmetry of a-b as it is measured and examined at the population level does n ot reflect canalization. (C) 1999 Wiley-Liss, Inc.