Parental effects and flight behaviour in the burying beetle, Nicrophorus vespilloides

Abstract

Parents play a key role in determining the phenotype of their offspring. However, relatively few studies have investigated whether parents can change their offspring's behaviour in a sustained way that persists into adulthood. With experiments on the burying beetle, Nicrophorus vespilloides, we investigated how the developmental environment created by parents affects their offspring's wing morphology in adulthood, and the correlated effects on adult flight behaviour. Burying beetles exhibit complex biparental care, but offspring can survive without parental provisioning. By removing parents just prior to hatching, while holding the nutritional environment constant, we investigated the downstream consequences for offspring morphology and behaviour. Larvae that developed in the absence of their parents had relatively long and more slender wings than those that developed in their parents' presence. Flight mill tests revealed that flight performance was dependent on the presence of parents during development but not on wing shape. Our results demonstrate that parents have long-lasting effects on the behaviour of their offspring, by influencing the morphology and flight behaviour of their young even after they have matured into adults.

Keywords: allometry; burying beetle; flight mill; geometric morphometrics; parental care; social evolution.

Figure 1

The configuration of the 17 landmarks used for the geometric morphometric analysis on wing shape variation.

Figure 2

The relationship between wing dimensions and body size, by sex and parental care treatment. Major axis regressions lines are shown and each data point represents a different beetle. (a) The relationship between wing length and pronotum width for males and females. (b) The relationship between wing area and pronotum width² for males and females. (c) The relationship between wing length and pronotum width for Full Care and Prehatching Care parental regimes. (d) The relationship between wing area and pronotum width² for Full Care and Prehatching Care parental regimes.

Figure 3

The effect of Full Care and Prehatching Care parental regimes on the relationship between body size and wing shape, expressed in terms of wing aspect ratio. Each data point represents a different beetle. Standardized major axis regression lines are shown.

Figure 4

Principal component analysis for the wing shape variation between Full Care and Prehatching Care beetles. Each data point represents the shape variation for a different beetle expressed as the relationship between the first two principal components. Ellipses represent the 95% confidence interval around the sample mean of the shape variation for each group (black straight line = Full Care; grey dashed line = Prehatching Care).

Figure 5

The variation in wing shape between beetles developed as larvae in Full Care or Prehatching Care conditions after a discriminant analysis with parental care treatment as the main effect. The mean shape for each group is visualized through a wireframe of straight lines connecting the landmarks used for the geometric morphometric analysis. Numbers indicate the landmarks used to perform the geometric morphometric analysis.

Figure 6

Frequency distributions of (a) total flight distance, (b) total flight duration, (c) average flight speed and (d) total number of flight events. Black bars represent individuals derived from the Full Care parental regime, white bars represent individuals derived from the Prehatching Care parental regime and light grey bars represent the overlapping distribution of the two care regimes.

Figure 7

The relationship between the ‘performance’ component of the overall flight performance and the care treatment. Box plots show 25% and 75% quartiles (boxes), medians (horizontal lines) and outermost values within the range of 1.5 times the respective quartiles (whiskers). ***P < 0.001.