The Journal of Heredity 1992:83(1):43-48
© 1992 The American Genetic Association 83:43-48
research-article |
Heritability of Body Size of Green Swordtails, Xiphophorus helleri: I. Sib Analyses of Males Reared Individually and in Groups
From the Department of Fisheries and Aquaculture, University of Florida 7922 N.W. 71st Street, Gainesville, FL 32606-0300
Abstract
The heritabilities of body length of male, green swordtails were estimated at five ages and at maturity by full-sib analyses. Male offspring from each of 32 maternal families were reared under two modes: (1) in groups of three sibs per tank (G-reared) and (2) individually in three separate tanks (I-reared). The estimated heritability of body length for I-reared males increased with increasing age, from 0.30 ± 0.09 at 70 days of age to 0.82 ± 0.23 at 305 days of age and at maturity. Conversely, the estimated heritability of length for G-reared males decreased with increasing age to a value of 0.12 ± 0.15 at 305 days of age. A matemal/common environmental effect appeared to be present at 70 and 105 days of age, but not thereafter. The major effect of group rearing was to increase substantially the within-family component of variance for size at sexual maturity. This led to a commensurate decrease in the variance among families and, hence, the estimated heritability. The phenotypic effects of group rearing were attributed to alterations of genetically determined maturation schedules, presumably induced by neuroendocrine responses to competition and behavioral interactions.