Application of microsatellite DNA markers to discriminate between maternaland genetic effects on scalation and behavior in multiply-sired garter snake litters

Incomplete knowledge of pedigrees sometimes limits the methods of estimatin g quantitative genetic parameters (heritability, genetic correlation) in na ture and may result in estimates that are inflated by nongenetic sources of variation. North American garter snakes and their allies provide a model s ystem for investigating evolutionary quantitative genetics, but estimates o f quantitative genetic parameters in these snakes are mostly based on offsp ring-dam regression and full-sib analysis, methods that fail to discriminat e between maternal genetic, maternal environmental, and direct genetic effe cts on traits of interest. Using data from the garter snake Thamnophis sirt alis, we demonstrate that microsatellite DNA markers can be used to identif y full-sib sireships within litters in species that produce large numbers o f offspring and in which multiple paternity is common. This allows estimati on of quantitative genetic parameters using a maternal half-sib analysis in which sires are nested within dams. Six microsatellite DNA loci were score d for four wild-caught dams and their 73 offspring and revealed two full-si b sireships within each litter. Maternal half-sib analyses of scalation and behavior suggest that heritability may be lower and maternal effects large r than was previously thought.