THE WIDOW EFFECT AND ITS CONSEQUENCES FOR REPRODUCTION IN BURYING BEETLES, NICROPHORUS VESPILLOIDES (COLEOPTERA, SILPHIDAE)

Burying beetles tend their young on small vertebrate carcasses, which serve as the sole source of food for the developing larvae. Single fem ales are as proficient at rearing offspring as male-female pairs, yet males opt to remain with their broods throughout most of the larval de velopment. One potential benefit of a male's extended residency is tha t it affords him the opportunity of additional copulations with the fe male, which could ensure his paternity in a replacement bred should th e female's first egg clutch fail to hatch. We tested this hypothesis b y manipulating males' access to their mates during the production of r eplacement clutches, using genetic colour markers to determine the pat ernity of offspring. Females were induced to produce a replacement bro od by removing their first clutch of eggs. In one experimental treatme nt, we removed the female's mate upon the removal of her first egg clu tch ('widowed' females); in a second treatment, the female was permitt ed to retain her mate up until she produced a replacement clutch. Ther e was no significant difference in paternity between males removed fro m females before the initiation of replacement clutches and those perm itted to remain with their mates. However, widowed females produced fe wer offspring in replacement broods than did females permitted to reta in their mates. This difference occurred primarily because a significa ntly greater proportion of widowed females opted not to produce a repl acement clutch, a result we refer to as the 'widow effect'. This widow effect was further shown in those replicates in which females of both treatments produced replacement clutches: widowed females took signif icantly longer to produce a replacement clutch than did females permit ted to retain their mates. Thr loss of her mate could be a signal to a female that a take-over of the carcass is imminent. Her reluctance to produce a replacement clutch under these circumstances might constitu te a strategy by which she conserves carrion for a subsequent reproduc tive attempt with an intruding male successful at ousting her previous mate. Regardless of its functional significance, the widow effect fav ours the extended residency of males and therefore contributes to the selective maintenance of male parental care.