Resource concealment and the evolution of parental care in burying beetles

Abstract

Comparative experimental study of species can provide insight into behavioral transitions in evolution. The insects offer many such examples for the analysis of parental care. We examined three distantly related species of Nicrophorus and two non-Nicrophorus silphid beetles for their ability to conceal odors from a carcass that cue competitors that attempt to usurp the resource. We predicted that species with well-developed parental care would exhibit a heightened ability to conceal a resource from competitors, even when differences in burying behavior and direct defense were experimentally eliminated. Carcasses were provided to male-female pairs in the laboratory for 3 days and then experimentally buried in the field, without parents, to assess discovery by Nicrophorus and vertebrate scavengers. The burying beetles Ni. orbicollis, Ni. sayi and Ni. pustulatus were far more successful in hiding a prepared resource (>76%) from free-flying Nicrophorus than the less parental Ptomascopus morio or Necrophila americana (<25%). Carcasses provided to P. morio and Ne. americana were also more likely to be discovered by Nicrophorus than non-prepared control carcasses, suggesting that microbially derived odor cues available to competitors were increased by non-Nicrophorus interaction with carcasses. In the absence of burial, carcass preparation had no effect on vertebrate scavenging. We hypothesize that the evolution of burying and carcass modification to conceal a discovered resource from diverse competitors, more so than control of microbial decay, was a critical step in the evolutionary transition to monopolization of a small carcass, nesting and extended parental care in the Silphidae.

Differences in sibling cooperation in presence and absence of parental care in a genus with interspecific variation in offspring dependence

“…Moreover, N. orbicollis may benefit less from parental carcass preparation in the absence of posthatching care than more independent species. In contrast to fresh carcasses, prepared carcasses are characterized by a parentally manipulated microbial community, which primarily helps to preserve and conceal the carcass from other necrophagous animals and conspecific competitors (Suzuki 1999;Trumbo and Sikes 2021;. However, the decaying processes of the carcass caused by carcass-and soil-borne microbes might act predigestive, facilitating larval self-feeding, especially among highly dependent species (Capodeanu-Nägler et al 2016).…”

Microbial volatiles and succession of beetles on small carrion

“…The sulphur‐VOCs may have originated as by‐products of amino acid metabolism and then been co‐opted for microbe–microbe competition (Ohga et al, 1993; Ossowicki et al, 2017); the sulphur‐VOCs are particularly effective against fungi (Mao et al, 2019; Tang et al, 2019; Tyc et al, 2015; Wang et al, 2021). Animals may not have been the original targets of sulphur‐VOCs, but beetles and flies exploit the public information that is readily available (Rhinesmith‐Carranza et al, 2018) and have evolved the ability to tolerate many of the toxins (Trumbo et al, 2016; Trumbo & Sikes, 2021). Nematodes and vertebrates may have become additional agents shaping the production of microbial toxins and volatiles, as microbes can deter these carrion competitors (Janzen, 1977; Yan et al, 2019).…”

Moving the corpse to hide the evidence: horizontal as well as vertical movement is important when burying beetles cache a carcass

“…Caching behavior (hiding and storing a resource) is common among vertebrates (Smith and Reichman 1984;Teurlings et al 2020;Allen et al 2021), but it is not always clear if the bene t is preservation against decomposition or prevention of usurpation (van der Veen et al 2020). Carrion that is buried is slower to be discovered by scavengers (Lundt 1964;Payne 1965;Shubeck and Blank 1982;Shubeck 1985;Teurlings et al 2020), especially when there are no holes in the carrion made by trauma or by feeding scavengers (Connell and Slatyer 1977;Mann et al 1990;Trumbo 2017;Trumbo and Sikes 2021).…”

“…Their chemical preferences also switch, as breeding beetles are attracted to methyl thiocyanate (MeSCN) but are repelled by chemicals associated with active decay (e.g., dimethyl trisul de, Trumbo and Steiger 2020) that can be attractive for feeding beetles (Podskalska et al 2009;von Hoermann et al 2013). The primary adaptive explanation for burial of a breeding resource, which includes digging beneath the resource while stripping it of hair or feathers, is thought to be to reduce competition (Pukowski 1933;Trumbo and Sikes 2021). Resident beetles also apply anal and oral secretions to the exposed carcass skin, altering the microbial community, slowing decomposition, and reducing volatile cues used by rivals (Trumbo 2017;Duarte et al 2018;Shukla et al 2018;).…”