Larval environmental conditions influence plasticity in resource use by adults in the burying beetle, Nicrophorus vespilloides

Abstract

Recent studies have shown that intraspecific patterns of phenotypic plasticity can mirror patterns of evolutionary diversification among species. This appears to be the case in Nicrophorus beetles. Within species, body size is positively correlated with the size of carrion used to provision larvae and parental performance. Likewise, among species, variation in body size influences whether species exploit smaller or larger carrion and the extent to which larvae depend on parental care. However, it is unclear whether developmental plasticity in response to carcass size, parental care, or both underlie transitions to new carcass niches. We examined this by testing whether variation in the conditions experienced by Nicrophorus vespilloides larvae influenced their ability to breed efficiently upon differently sized carcasses as adults. We found that the conditions experienced by larvae during development played a critical role in determining their ability to use large carcasses effectively as adults. Specifically, individuals that developed with parental care and on large carcasses were best able to convert the resources on a large carcass into offspring when breeding themselves. Our results suggest that parentally induced plasticity can be important in the initial stages of niche expansion.

Keywords: Burying beetle; diversification; parental care; parental effects; phenotypic plasticity.

Figure 1

An overview of the experimental design. Beetles were reared as larvae in one of four larval environments: Full Care/Large Carcass, Full Care/Small Carcass, No Care/Large Carcass, No Care/Small Carcass. Larvae from each treatment were bred as adults in one of two breeding environments: Large Carcass or Small Carcass. We allowed adults in all of these treatments to provide parental care. Sample sizes are in Table 1.

Figure 2

The impact of larval environmental conditions on the development of adult body size. The left panel (A) shows the effects of parental care and carcass size on larval mass at dispersal (mean ± SE), the middle panel (B) shows the relationship between mean larval mass at dispersal and mean adult pronotum width (with each symbol representing a different brood), and the right panel (C) shows the ultimate effects of parental care and carcass size on adult pronotum width (mean ± SE). In each panel, broods developing with or without parental care are shown with blue and red symbols, respectively. In panels (A) and (C), carcass size is indicated on the x‐axis. In panel (B), different carcass size treatments are indicated by different symbols (circles for small carcasses and squares for large carcasses).

Figure 3

The impact of the larval and adult environments on two measures of parental performance: brood size at dispersal (A) and mean larval mass (B). In each panel, the adult environment (small or large breeding carcass) is on the x‐axis and the different symbols and colors denote the larval environment: individuals developed as larvae with or without care (blue and red symbols, respectively) and on a small (circles with dashed lines) or large (squares with solid lines) carcass. Symbols represent means (mean ± SE).