Growth and Survivorship in a California Population of Gerrhonotus coeruleus, with Comments on Intraspecific Variation in Adult Female Size

Abstract

G. coeruleus is a viviparous lizard that ranges into high latitudes and altitudes in western North America. Females in a population on the northern coast of California (Mendocino County) [USA] reach sexual maturity in 32 mo. and produce a single litter each season. Relatively low clutch sizes (.hivin.X = 3.8 .+-. 0.2) contribute to low fecundity. Annual survivorship was approximately 73% for adults and 54% for juvenile lizards. Female survivorship exceeded male survivorship during 1974 and mean female size (87.7 .+-. 1.0 mm) was significantly larger than mean male size (83.6 .+-. 1.2 mm) the following year. Growth of females in a 2nd coastal population (Monterey County) was more rapid and these lizards were larger at sexual maturity than Mendocino County females. Females in a montane population (El Dorado County, Calif.) reached reproductive maturity when larger and older (44 mo.) than females in either coastal population although they attain a size in 32 mo. equal to Mendocino County females at the same age. Litter size, newborn size and relative clutch mass were significantly higher in the El Dorado County population. The evolution of delayed maturity and larger adult size in this species may result from selection for both larger litters and larger young.