Phenotypic variation in resource acquisition influences trade-off between number and mass of offspring in a burying beetle: Trade-off between number and mass of offspring

Abstract

Understanding the consequences of phenotypic variation in resource acquisition is an important problem in evolutionary ecology because such variation may impact on how parents balance resource investment in individual offspring against other life-history priorities. Here we investigate the effects of phenotypic variation in resource acquisition on the number and mass of offspring and the trade-off between the two in the burying beetle Nicrophorus vespilloides. We manipulate resource acquisition in adults by providing some females with a small mouse carcass (5–10 g) and other females with a large mouse carcass (15–20 g). We found that females breeding on larger carcasses produced both more and larger offspring than females breeding on smaller carcasses. Furthermore, an increase in brood size had a stronger negative effect on offspring mass in broods produced on smaller carcasses than in broods produced on larger carcasses. We conclude that phenotypic variation in resource acquisition had a strong effect on the number and mass of offspring and the trade-off between the two. Our study contributes to our understanding of phenotypic variation in resource acquisition by showing that females with more resources produce both more and larger offspring in situations where such variation is not associated with anatomical or physiological differences between females.