Thermal Ecology and Plasticity in the Burying Beetle, Nicrophorus orbicollis: An Observational Field Study

Abstract

Environmental temperatures are among the most significant factors affecting the ecology, behaviour, and evolution of organisms across all levels of biological organization. As such, understanding the impacts that natural thermal regimes have on organisms is central to the study of thermal ecology. Too often we, as ecologists, find ourselves drawing conclusions regarding interactions between temperature and organisms from laboratory studies using presumed optimal temperatures in studies of long-standing captive populations. Here, we used an observational field study to 1) describe the thermal ecology of a species of burying beetle, Nicrophorus orbicollis, 2) document natural associations between temperature and reproductive behaviours, and 3) document natural associations between temperature and traits related to fitness. We found that 1) the realized thermal regime inside brood chambers differed from both non-use subterranean sites and the soil surface, as well as from the temperatures commonly used in captive studies, 2) beetles buried carrion deeper when air temperatures were warmer, and 3) temperature inside the brood chamber predicted life-history traits: mean larval mass was lower when temperature variation increased and, contrary to previous findings of captive studies in our lab, overall brood size increased with mean temperatures. Our findings suggest that we should use caution when interpreting results from past captive work on N. orbicollis, as the conditions used in these studies may not reflect those seen in nature, leading to results with limited biological relevance. However, by producing a detailed description of the thermal ecology of N. orbicollis and supplying correlative evidence linking fitness components to temperature, our work aims to provide a more ecologically relevant context for future work on this species and burying beetles more generally, with the added benefit of being able to better predict how climate change may impact this and other similar species in the future.