Sexual size dimorphism and reproductive investment by female spiders: A comparative analysis

We investigate the association between female reproductive investment, abso lute size, and sexual size dimorphism in spiders to test the predictions of the fecundity-advantage hypothesis. The relationships between absolute siz e and sexual size dimorphism and aspects of female reproductive output are examined in comparative analyses using phylogenetically independent contras ts. We provide support for the idea that allometry for sexual dimorphism is the result of variation in female size more so than male size. Regression analyses suggest selection for increased fecundity in females. We argue tha t fecundity selection provides the only general explanation for the evoluti on of sexual size dimorphism in spiders.