Convariation of Spider Egg and Clutch Size: The Influence of Foraging and Parental Care

Abstract

The purpose of this study was to investigate the effects of body size, foraging mode, and parental care on the relationship between clutch size and egg size in spiders. Specifically, covariation of egg size and clutch size with body size was investigated, using data from the literature, in 156 species of North American spiders from 22 families. Variance in clutch size and egg size was found to be mainly attributed to differences among genera. I therefore conducted a comparative analysis at the generic level. Results indicated that clutch and egg size were influenced by body size. Spiders from genera with larger body sizes produced larger offspring and more offspring per reproductive event than spiders from genera with smaller sized species. Relative egg number was inversely related to size of eggs produced, indicating a reproductive trade—off. Web building spiders produced more and smaller eggs than cursorial hunting spiders of a similar body size. Furthermore, cursorial spiders that guard and carry their young produced more young than those that only guard the eggs before hatching or do not guard. However, residual clutch size or residual egg size (residuals from regressions of clutch size and egg size, respectively, against female body size) did not differ among parental care groups. This study suggests that the method of food acquisition and type of parental care contributed to the offspring are associated with clutch size and egg size in spiders.