The bacterial microbiome in spider beetles and deathwatch beetles

Abstract

The beetle family Ptinidae contains a number of economically important pests, such as the cigarette beetle Lasioderma serricorne, the drugstore beetle Stegobium paniceum, and the diverse spider beetles. Many of these species are stored product pests, which target a diverse range of food sources, from dried tobacco to books made with organic materials. Despite the threat that the 2,200 species of Ptinidae beetles pose, fewer than 50 have been surveyed for microbial symbionts, and only a handful have been screened using contemporary genomic methods. In this study, we screen 116 individual specimens that cover most subfamilies of Ptinidae, with outgroup beetles from closely related families Dermestidae, Endecatomidae, and Bostrichidae. We used 16S ribosomal RNA gene amplicon data to characterize the bacterial microbiomes of these specimens. The majority of these species had never been screened for microbes. We found that, unlike in their sister family, Bostrichidae, that has two mutualistic bacteria seen in most species, there are no consistent bacterial members of ptinid microbiomes. For specimens which had Wolbachia infections, we did additional screening using multilocus sequence typing and showed that our populations have different strains of Wolbachia than noted in previous publications.

Importance: Ptinid beetles are both household pests of pantry goods and economic pests of dried goods warehouses and cultural archives, such as libraries and museums. Currently, the most common pest control measures for ptinid beetles are phosphine and/or heat treatments. Many ptinid beetles have been observed to have increasing resistance to phosphine, and heat treatments are not appropriate for many of the goods commonly infested by ptinids. Pest control techniques focused on symbiotic bacteria have been shown to significantly decrease populations and often have the beneficial side effect of being more specific than other pest control techniques. This survey provides foundational information about the bacteria associated with diverse ptinid species, which may be used for future control efforts.

Keywords: Anobiidae; Bostrichidae; Bostrichoidea; Dermestidae; Ptinidae; Sodalis; Wolbachia.

Fig 1

Dendrogram of Bostrichoid families and ptinid subfamilies. While the relationships among the families are not fully known, this figure is based on previously published phylogenies and dendrograms combining genetic, morphological, and dietary information.

Fig 2

Bar plots of diversity metrics by subfamily (or family when subfamily was not identified). (A) Richness/alpha diversity, (B) evenness, and (C) Shannon diversity index.

Fig 3

Bar plots of diversity metrics for three subfamilies with specimens that are either wild caught or from a colony. (A) Richness/alpha diversity, (B) evenness, and (C) Shannon diversity index.

Fig 4

(A) NMDS plot comparing similarities between individuals in each bostrichid family. (B) NMDS plot comparing similarities between individuals based on families for outgroups (Bostrichidae, Dermestidae, and Endecatomidae) and subfamilies for ptinids. In cases where subfamily identification was not possible, the family is listed instead.

Fig 5

Stacked bar plot featuring the relative abundance of bacterial genera associated with each individual beetle. Any bacterial genera that had less than 3% of the relative abundance for at least one individual were grouped together under “remainder” for this plot. Bostrichids and dermestids are grouped by family, the remaining beetles are ptinids, which are grouped by subfamily, and then spaced by genera. The source of the beetle is indicated by a small symbol on top of each bar plot, where shape indicates wild versus lab colony, and color indicates specific population. Species with more than one individual in the data set are labeled with gray boxes beneath the bar plot.