The order Coleoptera (beetles) is arguably the most speciose group of animals, but the evolutionary history of beetles, including the impacts of plant feeding (herbivory) on beetle diversification, remain poorly understood. We inferred the phylogeny of beetles using 4,818 genes for 146 species, estimated timing and rates of beetle diversification using 89 genes for 521 species representing all major lineages and traced the evolution of beetle genes enabling symbiont-independent digestion of lignocellulose using 154 genomes or transcriptomes. Phylogenomic analyses of these uniquely comprehensive datasets resolved previously controversial beetle relationships, dated the origin of Coleoptera to the Carboniferous, and supported the codiversification of beetles and angiosperms. Moreover, plant cell wall-degrading enzymes (PCWDEs) obtained from bacteria and fungi via horizontal gene transfers may have been key to the Mesozoic diversification of herbivorous beetles—remarkably, both major independent origins of specialized herbivory in beetles coincide with the first appearances of an arsenal of PCWDEs encoded in their genomes. Furthermore, corresponding (Jurassic) diversification rate increases suggest that these novel genes triggered adaptive radiations that resulted in nearly half of all living beetle species. We propose that PCWDEs enabled efficient digestion of plant tissues, including lignocellulose in cell walls, facilitating the evolution of uniquely specialized plant-feeding habits, such as leaf mining and stem and wood boring. Beetle diversity thus appears to have resulted from multiple factors, including low extinction rates over a long evolutionary history, codiversification with angiosperms, and adaptive radiations of specialized herbivorous beetles following convergent horizontal transfers of microbial genes encoding PCWDEs.

Peruvian biodiversity is pivotal for conserving and managing natural resources, food security, poverty reduction, health, biosecurity, new industrial product development, and ecotourism (Smith et al., 2011). Geotrupidae Diversity in Peru: 1 subfamily, 4 genera, and 11 species. Recognition: The body shape is oval or round, and the head is not deflexed. The antennae are 11-segmented with a 3-segmented, opposable club with all antennomeres tomentose. The eyes are completely or partially divided by a canthus. The clypeus is often with a tubercle or horn. The labrum is truncate, prominent, and produced beyond the apex of the clypeus. The mandibles are prominent and produced beyond the apex of the labrum. The pronotum is convex with a base wider than or subequal to the elytral base and with or without tubercles, ridges, horns, or sulci. The elytra are convex, with or without striae. The pygidium is concealed by the elytra (Jameson, 2002a). Habitat: Life histories of the geotrupids are diverse, and food habits vary from saprophagous to coprophagous and mycetophagous. Adults of most species are secretive, living most of their life in burrows. Although adults do not tend larvae, adults provision food for larvae in brood burrows. Adults dig vertical burrows (15-200 cm in depth) and provision larval cells with dead leaves, cow dung, horse dung, or humus. Burrows of some species extend to a depth of 3.0 m (Jameson, 2002a). Notes: The family Geotrupidae includes 68 genera and about 620 species (Scholtz and Browne, 1996). The subfamily Geotrupinae does not occur in South America.

IntroductionWood digestion in insects relies on the maintenance of a mosaic of numerous microhabitats, each colonized by distinct microbiomes. Understanding the division of digestive labor between these microhabitats- is central to understanding the physiology and evolution of symbiotic wood digestion. A microhabitat that has emerged to be of direct relevance to the process of lignocellulose digestion is the surface of ingested plant material. Wood particles in the guts of some termites are colonized by a specialized bacterial fiber-digesting microbiome, but whether this represents a widespread strategy among insect lineages that have independently evolved wood-feeding remains an open question.MethodsIn this study, we investigated the bacterial communities specifically associated with wood fibers in the gut of the passalid beetle Odontotaenius disjunctus. We developed a Percoll-based centrifugation method to isolate and enrich the wood particles from the anterior hindgut, allowing us to access the wood fibers and their associated microbiome. We then performed assays of enzyme activity and used short-read and long-read amplicon sequencing of the 16S rRNA gene to identify the composition of the fiber-associated microbiome.ResultsOur assays demonstrated that the anterior hindgut, which houses a majority of the bacterial load, is an important site for lignocellulose digestion. Wood particles enriched from the anterior hindgut contribute to a large proportion of the total enzyme activity. The sequencing revealed that O. disjunctus, like termites, harbors a distinct fiber-associated microbiome, but notably, its community is enriched in insect-specific groups of Lactococcus and Turicibacter.DiscussionOur study underscores the importance of microhabitats in fostering the complex symbiotic relationships between wood-feeding insects and their microbiomes. The discovery of distinct fiber-digesting symbionts in O. disjunctus, compared to termites, highlights the diverse evolutionary paths insects have taken to adapt to a challenging diet.

Abstract. Cyclocephaline scarabs, the second largest tribe of rhinoceros beetles, are important pollinators of early-diverging angiosperm families in the tropics. The evolutionary history of cyclocephaline genera is poorly resolved and several genera are thought to be nonmonophyletic. We assess the monophyly of Mimeoma Casey, a group of Neotropical palm-feeding scarabs, and its relationship to Cyclocephala with a phylogenetic analysis of 2899 bp of DNA sequence data and 18 morphological characters. All five species of Mimeoma were included in analyses along with species of Cyclocephala Dejean, Dyscinetus Harold and Tomarus Erichson as outgroup taxa. Nearly complete 28S, 12S and CO1 data were collected from 26 of 29 specimens, of which 16 samples were pinned, museum specimens. 28S data strongly support a nonmonophyletic Mimeoma; mitochondrial data (CO1 and 12S) suggest that Mimeoma species are nested within an apical clade of other Cyclocephala species; combined molecular and morphological data identify two strongly supported clades of Mimeoma species but do not support their sister relationship. Combined data show that Mimeoma species are nested within Cyclocephala, thus rendering Cyclocephala paraphyletic. Mimeoma is synonymized within Cyclocephala resulting in the following new combinations: Cyclocephala acuta Arrow n.comb., Cyclocephala englemani (Ratcliffe) n.comb., Cyclocephala maculata Burmeister n.comb., Cyclocephala nigra (Endrödi) n.comb. and Cyclocephala signatoides Höhne n.comb. Our results demonstrate that pinned, museum specimens can be used to obtain DNA sequence data (particularly high-copy gene regions) for evolutionary studies, and provide the first empirical support that host-plant associations within cyclocephaline scarab clades are conserved at the plant family-level.