Social dilemma in the external immune system of the red flour beetle? It is a matter of time

Abstract

Sociobiology has revolutionized our understanding of interactions between organisms. Interactions may present a social dilemma where the interests of individual actors do not align with those of the group as a whole. Viewed through a sociobiological lens, nearly all interactions can be described regarding their costs and benefits, and a number of them then resemble a social dilemma. Numerous experimental systems, from bacteria to mammals, have been proposed as models for studying such dilemmas. Here, we make use of the external immune system of the red flour beetle, Tribolium castaneum, to investigate how the experimental duration can affect whether the external secretion comprises a social dilemma or not. Some beetles (secretors) produce a costly quinone‐rich external secretion that inhibits microbial growth in the surrounding environment, providing the secretors with direct personal benefits. However, as the antimicrobial secretion acts in the environment of the beetle, it is potentially also advantageous to other beetles (nonsecretors), who avoid the cost of producing the secretion. We test experimentally if the secretion qualifies as a public good. We find that in the short term, costly quinone secretion can be interpreted as a public good presenting a social dilemma where the presence of secretors increases the fitness of the group. In the long run, the benefit to the group of having more secretors vanishes and becomes detrimental to the group. Therefore, in such seminatural environmental conditions, it turns out that qualifying a trait as social can be a matter of timing.

Antifeedant Activities of Lignans from Stem Bark of Zanthoxylum armatum DC. against Tribolium castaneum

“…According to reports, the damages to stored grains and their related grain products by storage pests could be as high as 20–30% in tropical countries [ 2 ]. As an invertebrate model organism, T. castaneum is used in various biological disciplines, including developmental biology, immunology, evolutionary studies, and ecology [ 3 , 4 , 5 ]. Nowadays, synthetic insecticides have been commonly and heavily used to protect stored grains and their related products against pests.…”

Secretion and Detection of Defensive Compounds by the Red Flour Beetle Tribolium castaneum Interacting with the Insect Pathogenic Fungus Beauveria bassiana

“…Some studies have demonstrated that both benzoquinones (MBQ and EBQ) are differentially produced between individuals by genetic control [ 25 ], acting not only as repellents or deterrents, but also as spacing pheromones [ 26 ]. Benzoquinones secretion has been proposed as a social dilemma, since due to its properties it first increases the fitness of the colony, but over longer periods of time it becomes detrimental to the group [ 27 ]. Thus, in such semi-natural environmental conditions, qualifying a trait as social or not might be a matter of timing [ 27 ].…”

Immune StimulationviaWounding Alters Chemical Profiles of AdultTribolium castaneum

“…If wounding, e.g., via intraspecific cannibalism or interspecific competition, stimulates increased secretion of BQs, this can in turn signal overcrowding (Faustini & Burkholder, 1987; Verheggen et al, 2007) and result in further interference competition mediated by BQs (Khan et al, 2018; Sonleitner & Gutherie, 1991) or even dispersal (Duehl et al, 2011; Ogden, 1969), thereby influencing group dynamics and population size. Because flour conditioning and chemical cues affect the development, behaviour and survival of beetles (Joop et al, 2014), we hypothesise that differential changes in stink gland secretions in response to individual immune experiences are likely contributing to niche construction of flour beetles (Gokhale et al, 2017; Joop et al, 2014) by 1) regulating the pathogenic threat experienced by themselves and other conspecifics (Joop et al, 2014) and 2) mediating aggregation or dispersal behaviours of conspecifics (Duehl et al, 2011). The later process prompts the adjacent conspecifics to disperse into new environments, i.e.…”

“…The amount of secretion might therefore be optimised by evolution (Joop et al, 2014) and adjusted to external conditions (Pedrini et al, 2010). In theory, the level or composition of the beetles’ secretions inside the flour could be recognised by conspecifics and used for a potential adjustment of production and release of own secretions (Gokhale et al, 2017).…”