VARIATION IN BROWN SNAKE (STORERIA-DEKAYI) MORPHOLOGY AND SCALATION -SEX, FAMILY, AND MICROGEOGRAPHIC DIFFERENCES

Sex, family and microgeographic variation in body size, head dimension s, tail length, and scalation were assessed from 273 wild-caught brown snakes (Storeria dekayi) from seven island and mainland sites near La ke Erie and from 145 neonates born to 25 wild-caught females. Signific ant differences between males and females were present both in wild-ca ught snakes and in neonates, with females exceeding males in snout-ven t length and number of ventral scales and males exceeding females in t ail length, head dimensions, and number of subcaudal scales. Previous analyses have typically focused on the effect that sex differences mig ht have on adult snakes, e.g., in foraging or reproduction. The presen ce of sex differences among neonates raises the possibility that these differences may be of ecological and evolutionary significance in you nger snakes as well. Significant differences among families were found in neonates for all characters except number of labial scales, and si gnificant heritability (estimated from offspring-dam regression) was f ound for tail length, head length, and numbers of ventral, subcaudal, and temporal scales. Heritable variation in scalation is well known, b ut this is the first study to document heritable variation in snake mo rphology. This result is important because heritable variation is an i mplicit assumption of hypotheses for the evolution of sex, population, and species differences in morphology. Significant differences among sites were found for adult snout-vent length, head dimensions, number of subcaudal scales, and number of temporal scales. In addition, signi ficant phenotypic correlations (e.g., among head dimensions, between t ail length and number of subcaudal scales, between snout-vent length a nd number of ventral scales) and genetic correlations (e.g., between t ail length and number of subcaudal scales, between head length and num ber of ventral scales) were found between pairs of traits. The presenc e of these correlations suggests that groups of traits may be influenc ed by the same genetic or ontogenetic processes and may exhibit patter ns of correlated evolution.