Too much information: subordinate species disadvantaged by greater release of volatiles from resources

Abstract Volatile chemical cues produced by microbes provide essential information for animals. The quantity of volatiles available is related to temperature, directly by vapor pressure and indirectly by changes in microbial activity. We know little, however, about how these cues alter interspecific competition, structure communities or influence geographic distributions. We examined competition among a guild of burying beetles (Nicrophorus spp.) that use interference competition to gain control of their breeding resource, a small vertebrate carcass. Carcasses were placed in the field supplemented with the volatile methyl thiocyanate or dimethyl trisulfide, or as controls. For the genus as a whole, methyl thiocyanate was an attractant, increasing discovery of carcasses while dimethyl trisulfide was a deterrent, decreasing discovery. Not all species were affected equally. Nicrophorus sayi, N. orbicollis, and N. tomentosus were more likely to control carcasses supplemented with methyl thiocyanate compared to controls, while the smallest, least competitive species (N. defodiens) was less likely to control methyl thiocyanate-supplemented carcasses. Two follow-up experiments demonstrated that methyl thiocyanate did not deter N. defodiens from locating carcasses in the field or breeding on them in the laboratory. It is hypothesized that the inability of N. defodiens to maintain populations in southern geographic regions in North America is due to the increased production of microbially derived infochemicals at warmer temperatures that preferentially benefit its rivals. The results suggest that in contrast to other types of climate stress, the increase in resource-related volatiles expected to occur with rising temperatures may favor competitive dominant rather than subordinate species.