A test of the reproductive cost hypothesis for sexual size dimorphism in Yarrow's spiny lizard Sceloporus jarrovii

摘要: Summary 1 Trade-offs between reproduction and growth are central assumptions of life-history theory, but their implications for sexual size dimorphism (SSD) poorly understood. 2 Adult male Yarrow's spiny lizards Sceloporus jarrovii average 10% larger than adult females. In a low-altitude (1700 m) population, this SSD develops because males grow more quickly females during the first year life, particularly female reproductive season. This study tests hypothesis that is constrained by energetic costs reproduction. 3 To test cost reproduction, I compared rates free-living differed, either naturally or experimentally, in status. Females delayed until second grew reproduced as yearlings, ovariectomized yearlings to sizes controls. 4 To determine whether absence inferred cost, also studied high-altitude (2500 m) population which all delay year. Sex differences trajectories were similar those observed at low altitude, such averaged even prior reproduction. 5 Although may be multiple lines evidence indicate insufficient explain full magnitude S. jarrovii. First, nonreproductive not final month gestation, time already well developed. Second, benefit accruing from experimental inhibition accounts only 32% natural sex difference body size. Finally, advance with maturation.