Geographic variation in age and size at maturity in a small Australian viviparous skink
Wapstra, E and Swain, R and O'Reilly-Wapstra, JM, Geographic variation in age and size at maturity in a small Australian viviparous skink, Copeia, 2001, (3) pp. 646-655. ISSN 0045-8511 (2001) [Refereed Article]
Age and size at maturity are pivotal life-history traits through their effects on other key traits, such as annual and lifetime fecundity. We used skeletochronology to investigate the relationships among size (snout-vent length), age, and maturity in two populations of a small viviparous skink, Niveoscincus ocellatus, from Tasmania, Australia. The species occupies a wide geographic and climatic range within the temperate zone, and we chose populations from the climatic extremes of this range. Growth in N. ocellatus is rapid early in life but slows considerably after maturity in both sexes. Within sites, we found no difference in growth patterns or length at maturity between the sexes. However, there were large differences between sites. At our "warm" site, lizards were mature at three years of age at a relatively small size. Lizards from the "cold" site typically delayed maturity until their fourth year (although some males were mature at the end of their third year); as a result, they were significantly larger at maturity and thereafter remained larger for any age than did warm-site lizards. These patterns are consistent with predictions from models of the proximate influence of the thermal environment on growth and maturity patterns in squamate reptiles. Lizards from the cold site are born later in the season and have a shorter activity season prior to obligatory winter hibernation, and conditions for growth are less favorable in any particular month than at the warm site. Because delaying maturity is cosily to current fecundity, we suggest that in N. ocellatus lifetime fecundity is enhanced at the cold site by additional growth and gains in future fecundity through the relationship between body length and reproductive output.