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The burying beetle (Nicrophorus vespilloides) is thought to be predominantly sexually monomorphic. Males carry an additional abdominal segment and produce pheromones, but otherwise the sexes are alike.Both sexes bear bright orange bands on their black elytra, which probably function as part of a warning display rather than in mate choice. In wild populations, the sexes do not differ in mean body size, nor in its variation.Here we describe a form of sexual size dimorphism in wild populations that has previously been overlooked. We show that males have wider heads than females, for any given pronotum width (body size), and that the scaling relationship between head width and pronotum width is hyperallometric in males, but isometric in females. We also show how absolute head width, as well as the extent of sexual dimorphism in head width, differs among seven wild populations inhabiting different woodlands that are within c.10 km of each other.We suggest that head size dimorphism is functionally related to bite force. We hypothesise that dimorphism could be due to divergent selection arising from task specialisation during biparental care, as the duties of care favoured by males are likely to require a greater bite force. [ABSTRACT FROM AUTHOR]

Insects can adjust their behaviour in relation to experience in a wide range of contexts including foraging, mate selection and choice of oviposition site. Here, we investigate whether burying beetles Nicrophorus vespilloides modulate their choice of carrion type in relation to the outcome of their past breeding experience.Burying beetles require the carcass of a small vertebrate, such as a mouse or a chick, to reproduce. Beetle parents convert this carrion into an edible nursery for their larvae, whom they typically care for throughout larval development. We tested whether a beetle's past breeding experience influenced its subsequent choice of carrion when presented simultaneously with either a dead mouse or a dead chick.We found that beetles that bred on a mouse and produced many larvae in their first breeding attempt subsequently favoured mice over chicks for their second breeding attempt. Beetles that had produced fewer larvae on a dead mouse switched to favouring dead chicks in their second breeding attempt. Those that had bred on a dead chick chose carrion at random subsequently, regardless of their previous breeding success.Our general conclusion is that burying beetles can integrate different sources of information about their past breeding experience with current cues when selecting carrion for reproduction. [ABSTRACT FROM AUTHOR]

Principles of social evolution have long been used retrospectively to interpret social interactions, but have less commonly been applied predictively to inform conservation and animal husbandry strategies. We investigate whether differences in developmental environment, facilitated by divergent social conditions, can predict resilience to environmental change. Upon exposure to harsh novel environments, populations that previously experienced more benign social environments are predicted either to suffer fitness losses (the "mutation load hypothesis" and "selection filter hypothesis") or maintain fitness (the "beneficial mutation hypothesis"). We tested these contrasting predictions using populations of burying beetles Nicrophorus vespilloides we had evolved experimentally for 45 generations under contrasting social environments by manipulating the supply of post-hatching parental care. We exposed sexually immature adults from each population to varying heat stress and measured the effect on survival and reproduction. The greater the level of parental care previously experienced by a population, the better its survival under heat stress during sexual maturation. Although this is consistent with the "beneficial mutation hypothesis," it is also possible that populations that had evolved without post-hatching care were simply more prone to dying during maturation, regardless of their thermal environment. Overall, we suggest that stochastic genetic variation, probably due to founder effects, had a stronger influence on resilience. We discuss the implications for translocation and captive breeding programs. [ABSTRACT FROM AUTHOR]

For organisms in temperate environments, seasonal variation in resource availability and weather conditions exert fluctuating selection pressures on survival and fitness, resulting in diverse adaptive responses. By manipulating resource availability on a local spatial scale, we studied seasonal patterns of resource use within natural populations of burying beetles Nicrophorus vespilloides in a Norfolk woodland. Burying beetles are necrophagous insects that breed on vertebrate carcasses. They are active in Europe between April and October, after which they burrow into the soil and overwinter. Using breeding and chemical analyses, we compared the fecundity and physiological state of beetles that differed in their seasonal resource use. We found seasonal variation in carrion use by wild burying beetles and correlated differences in their reproductive success and cuticular hydrocarbon profiles. Our results provide novel insight into the seasonal correlates of behaviour, physiology and life history in burying beetles. [ABSTRACT FROM AUTHOR]