Variation among clutches in the response of spiders to prey nutrient content

Abstract

The phenotype of animals is often determined by an interaction between genes and the environment. In spiders, recent work has shown that the nutritional composition of prey can have a large effect on the growth and reproduction of spiders. I tested whether the growth of juvenile spiderlings was affected by an interaction between the clutch and the diet on which they fed (i.e., high or low nutrient) in both a wandering (Tigrosa helluo (Walckenaer 1837)) and a web-building (Pholcus phalangioides Fuesslin 1775) spider. Diet was manipulated by feeding spiderlings similar quantities of food that varied in their nutritional composition. The results for both species followed the same pattern. Overall, spiderlings fed the high-nutrient prey were larger, both in terms of mass and body size. However, there was significant variation in effect size among clutches, with some clutches showing large effects of nutrients on growth and other clutches showing little or no effect of nutrients on growth. In both species, there were no differences among clutches in the final mass and size of individuals on the low nutrient treatment. The differences among clutches were due to differences in the mass and size of spiderlings on the high nutrient treatments. These results highlight the importance of incorporating a diverse range of clutches or genotypes in studies of spider nutrition to ensure that the results are generalizable and not biased by particular genotypes or clutches.