Starving the competition: a proximate cause of reproductive skew in burying beetles (Nicrophorus vespilloides)

Abstract

Proximate mechanisms underlying reproductive skew are obscure in many animals that breed communally. Here, we address causes of reproductive skew in brood-parasitic associations of burying beetles (Nicrophorus vespilloides). Male and female burying beetles feed and defend their larvae on buried carcasses. When several females locate the same small carcass, they engage in violent physical altercations. The subordinate then acts as an intraspecific brood parasite, laying eggs, but not providing care. The dominant female largely monopolizes access to the carcass; she alone provides parental care and her share of the brood is much larger than the subordinate's. On larger carcasses, subordinates have greater access to the carcass than on small ones, and reproductive skew is reduced. Differential fecundity, ovicide and larvicide have been suggested as causes of skew on small carcasses. Here, we report the results of the experiments pertaining to the first two of these potential mechanisms. Ovicide did not significantly contribute to reproductive skew on small carcasses, but differential fecundity did. Fecundity differences were due to dominance status, not body size per se. Fecundity differences disappeared when supplemental food was available, suggesting that reduced access to the carcass limits fecundity by causing nutritional deficiencies. Supplemental food prevented such nutritional deficiencies and allowed subordinates to produce as many eggs as dominants. Apparently, aggressive behaviour by dominants functions in the context of reproductive competition, limiting subordinate reproduction by preventing food intake on the carcass.

Drosophila females trade off good nutrition with high quality oviposition sites when choosing foods

“…In nature, nutritional decisions can be complicated by several additional factors such as social information provided by other females (Battesti et al, 2012;Durisko et al, 2014;Lihoreau et al, 2016;Sarin and Dukas, 2009;Chabaud et al, 2009), competition (Eggert et al, 2008;Salomon et al, 2008), sexual interactions with males (Chapman and Partridge, 1996;Gorter et al, 2016) or the presence of beneficial microbial communities on foods (Venu et al, 2014;Wong et al, 2015). Thanks to their unique association with food as shelter, breeding sites and sources of nutrients, fruit flies hold considerable promise as model organisms with which to study these multi-level nutritional interactions within the extended integrative framework of nutritional ecology (Simpson et al, 2015a).…”

Contest behavior and other reproductive efforts in aging breeders: a test of residual reproductive value and state-dependent models

“…Age, dominance status, and injury might well have independent effects on fecundity when two females compete, but the small sample size for some combinations of variables did not permit a more detailed analysis. Using N. vespilloides, Eggert et al (2008) demonstrated that limited access to the resource negatively affected fecundity in subordinate females. In previous works on Nicrophorus spp., the effects of age on food provisioning and the total mass of the brood were likewise variable and sometimes negative (Scott 1998;Lock et al 2007;Creighton et al 2009;Trumbo 2009;Cotter et al 2011).…”

“…During the 4 days with the carcass, dominant females gained a mean (± SD) of 9.9 (±3.7 %) while subordinate females lost a mean of 15.3 (± 5.6 %) of their body mass compared to the start of the contest. This occurs because the dominant female feeds on the resource and restricts the subordinate's access (Eggert et al 2008). The female in possession of the carcass on day 4 was always heavier than the subordinate female (n042), regardless of the nutritional treatment prior to the trial (p< 0.001).…”

Recognition and Family Life: Recognition Mechanisms in the Biparental Burying Beetle

“…Lab as well as field studies have shown that the brood contains on average 6 % parasite offspring, often not more than one to two young . Although the reproductive skew can partly be explained by the loser's inability to produce as many eggs as the winner because of limited access to the carcass and therefore nutrition (Eggert et al 2008), two different mechanisms of parent-offspring recognition has been found to contribute to the lower reproductive success of the subordinate female. In N. tomentosus (Scott 1997), but not in N. vespilloides (Eggert et al 2008), there is some evidence that females increase the proportion of own offspring in a brood by selective ovicide.…”

“…Although the reproductive skew can partly be explained by the loser's inability to produce as many eggs as the winner because of limited access to the carcass and therefore nutrition (Eggert et al 2008), two different mechanisms of parent-offspring recognition has been found to contribute to the lower reproductive success of the subordinate female. In N. tomentosus (Scott 1997), but not in N. vespilloides (Eggert et al 2008), there is some evidence that females increase the proportion of own offspring in a brood by selective ovicide. Although it is not known how they are able to discriminate between their own eggs and the foreign ones, it is possible that individual specific cuticular lipids or other chemicals left behind on the egg surface serve as recognition cues (see e.g.…”