The proximate cause of asynchronous hatching in the burying beetle Nicrophorus quadripunctatus

Abstract

In some species, a brood hatches or is born asynchronously over an extended period of time. This asynchronous hatching establishes competitive asymmetries between offspring, and younger offspring usually exhibit a higher mortality risk and/or lower growth rate. A large body of research suggests that selection favours asynchronous hatching, though a consensus is yet to be reached on the nature of its adaptive benefits. One of the possible causes of this is that previous studies have focused mostly on avian species, who must incubate their eggs. Thus, studying non-avian species may provide an opportunity to improve our understanding of the wider importance of asynchronous hatching, for example in invertebrates, which do not incubate their eggs. In the burying beetle, Nicrophorus quadripunctatus, asynchronous hatching has been shown to maximize parental fitness. However, there is currently no information on the proximate cause of asynchronous hatching in this species. Here we investigated the influence of timing of egg-laying and the duration of embryonic development on the timing of hatching. We found that the timing of egg-laying by the parent was a major determinant of the timing of hatching, although the duration of embryonic development was also important. Our results suggest that the principal proximate cause of asynchronous hatching is parental asynchronous egg-laying.