Joseph V. McHugh

The Beetle Gut: A Hyperdiverse Source of Novel Yeasts

We isolated over 650 yeasts over a three year period from the gut of a variety of beetles and characterized them on the basis of LSU rDNA sequences and morphological and metabolic traits. Of these, at least 200 were undescribed taxa, a number equivalent to almost 30% of all currently recognized yeast species. A Bayesian analysis of species discovery rates predicts further sampling of previously sampled habitats could easily produce another 100 species. The sampled habitat is, thereby, estimated to contain well over half as many more species as are currently known worldwide. The beetle gut yeasts occur in 45 independent lineages scattered across the yeast phylogenetic tree, often in clusters. The distribution suggests that the some of the yeasts diversified by a process of horizontal transmission in the habitats and subsequent specialization in association with insect hosts. Evidence of specialization comes from consistent associations over time and broad geographical ranges of certain yeast and beetle species. The discovery of high yeast diversity in a previously unexplored habitat is a first step toward investigating the basis of the interactions and their impact in relation to ecology and evolution.

Wood ingestion by passalid beetles in the presence of xylose‐fermenting gut yeasts

During a survey of insect gut micro‐organisms, we consistently isolated Pichia stipitis‐like yeasts (Fungi: Ascomycota, Saccharomycetes) from the wood‐ingesting beetles, Odontotaenius disjunctus and Verres sternbergianus (Coleoptera: Passalidae). The yeasts were isolated from passalid beetles over a wide area, including the eastern and midwestern USA and Panama. Phylogenetic analyses of the nuclear encoded small and large subunit rRNA gene (rDNA) sequences distinguished a well‐supported clade consisting of the passalid yeasts and Pichia stipitis, P. segobiensis, Candida shehatae and C. ergatensis. Members of this clade have the ability to ferment and assimilate xylose or to hydrolyse xylan, major components of the polysaccharide, hemicellulose. Sexual reproduction was present in the passalid isolates but was rare among the gut yeasts of other beetles to which they were compared. Minor genetic and phenotypic variation among some of the passalid yeasts was detected using markers from the internal transcribed spacer region of the rDNA repeat unit, morphology, and in vitro metabolic tests. The consistent association of xylose‐fermenting yeasts of almost identical genotypes with passalid beetles across a broad geographical distribution, suggests a significant symbiotic association.

The beetle tree of life reveals that Coleoptera survived end‐Permian mass extinction to diversify during the Cretaceous terrestrial revolution

Here we present a phylogeny of beetles (Insecta: Coleoptera) based on DNA sequence data from eight nuclear genes, including six single‐copy nuclear protein‐coding genes, for 367 species representing 172 of 183 extant families. Our results refine existing knowledge of relationships among major groups of beetles. Strepsiptera was confirmed as sister to Coleoptera and each of the suborders of Coleoptera was recovered as monophyletic. Interrelationships among the suborders, namely Polyphaga (Adephaga (Archostemata, Myxophaga)), in our study differ from previous studies. Adephaga comprised two clades corresponding to Hydradephaga and Geadephaga. The series and superfamilies of Polyphaga were mostly monophyletic. The traditional Cucujoidea were recovered in three distantly related clades. Lymexyloidea was recovered within Tenebrionoidea. Several of the series and superfamilies of Polyphaga received moderate to maximal clade support in most analyses, for example Buprestoidea, Chrysomeloidea, Coccinelloidea, Cucujiformia, Curculionoidea, Dascilloidea, Elateroidea, Histeroidea and Hydrophiloidea. However, many of the relationships within Polyphaga lacked compatible resolution under maximum‐likelihood and Bayesian inference, and/or lacked consistently strong nodal support. Overall, we recovered slightly younger estimated divergence times than previous studies for most groups of beetles. The ordinal split between Coleoptera and Strepsiptera was estimated to have occurred in the Early Permian. Crown Coleoptera appeared in the Late Permian, and only one or two lineages survived the end‐Permian mass extinction, with stem group representatives of all four suborders appearing by the end of the Triassic. The basal split in Polyphaga was estimated to have occurred in the Triassic, with the stem groups of most series and superfamilies originating during the Triassic or Jurassic. Most extant families of beetles were estimated to have Cretaceous origins. Overall, Coleoptera experienced an increase in diversification rate compared to the rest of Neuropteroidea. Furthermore, 10 family‐level clades, all in suborder Polyphaga, were identified as having experienced significant increases in diversification rate. These include most beetle species with phytophagous habits, but also several groups not typically or primarily associated with plants. Most of these groups originated in the Cretaceous, which is also when a majority of the most species‐rich beetle families first appeared. An additional 12 clades showed evidence for significant decreases in diversification rate. These clades are species‐poor in the Modern fauna, but collectively exhibit diverse trophic habits. The apparent success of beetles, as measured by species numbers, may result from their associations with widespread and diverse substrates – especially plants, but also including fungi, wood and leaf litter – but what facilitated these associations in the first place or has allowed these associations to flourish likely varies within and between lineages. Our results provide a uniquely well‐resolved temporal and phylogenetic framework for studying patterns of innovation and diversification in Coleoptera, and a foundation for further sampling and resolution of the beetle tree of life.

Cladistic analysis of the fire ants of the Solenopsis saevissima species-group (Hymenoptera: Formicidae)

Results are presented from a phylogenetic study of the fire ants comprising the Solenopsis saevissima species‐group (Hymenoptera: Formicidae). Six most‐parsimonious trees were identified following a cladistic analysis utilizing 18 taxa and 36 morphological characters derived from three castes and two developmental stages. A strict consensus tree recovered the following relationships: (S. daguerrei ((S. electra, S. pusilignis) (S. saevissima (S. pythia (S. interrupta, S. ‘undescribed species’, S. weyrauchi (S. richteri, S. invicta (S. megergates (S. quinquecuspis, S. macdonaghi)))))))). This phylogenetic hypothesis implies trends in fire ant evolution towards both polygyny (multiple egg‐laying queens per colony) and large major worker size. The phylogeny also provides a test of Emerys Rule, which is not supported in its strictest sense because the social parasite S. daguerrei is not the sister species to its host species. A modified version of Emerys Rule is supported, because the social parasite is the sister species to a larger clade containing its hosts, as well as nonhosts.

A phylogenetic study of Dermestidae (Coleoptera) based on larval morphology

Abstract.  The results of a phylogenetic analysis of Dermestidae (Coleoptera) based on the morphology of immature stages are presented and implications for the classification of the family are discussed. The monophyly of ((Orphilus) + (Dermestidae) + (Endecatomidae (Bostrichidae + Anobiidae))) is strongly supported. Dermestidae, excluding Orphilus Erichson, forms a monophyletic group. The phylogenetic position of the Orphilinae remains enigmatic. The hypothesized relationships of the remaining dermestid subfamilies are (Thorictinae (Dermestinae (Attageninae (Megatominae + Trinodinae)))). Phylogenetically informative morphological characters of larvae and pupae are illustrated and described. Character state transformations implied by the phylogenetic hypothesis are discussed. New morphological observations are provided, including the first records of the presence of gastric caeca in the larva of Dermestes L., and the first report of the number of Malpighian tubules and the number of abdominal ganglia in Dermestidae, Bostrichidae, Anobiidae, Nosodendridae and Derodontidae. The form of the mandibular base is described for the first time for Thylodriini Beal and Trinodini Beal. The fossil record and distribution of extant Dermestidae are discussed in the light of the phylogenetic hypothesis. The origin of the family is hypothesized to be in the Late Cretaceous.

Phylogeny and classification of Cucujoidea and the recognition of a new superfamily Coccinelloidea (Coleoptera: Cucujiformia)

A large‐scale phylogenetic study is presented for Cucujoidea (Coleoptera), a diverse superfamily of beetles that historically has been taxonomically difficult. This study is the most comprehensive analysis of cucujoid taxa to date, with DNA sequence data sampled from eight genes (four nuclear, four mitochondrial) for 384 coleopteran taxa, including exemplars of 35 (of 37) families and 289 genera of Cucujoidea. Maximum‐likelihood analyses of these data present many significant relationships, some proposed previously and some novel. Tenebrionoidea and Lymexyloidea are recovered together and Cleroidea forms the sister group to this clade. Chrysomeloidea and Curculionoidea are recovered as sister taxa and this clade (Phytophaga) forms the sister group to the core Cucujoidea (Cucujoidea s.n.). The nitidulid series is recovered as the earliest‐diverging core cucujoid lineage, although the earliest divergences among core Cucujoidea are only weakly supported. The cerylonid series (CS) is recovered as monophyletic and is supported as a major Cucujiform clade, sister group to the remaining superfamilies of Cucujiformia. Currently recognized taxa that were not recovered as monophyletic include Cucujoidea, Endomychidae, Cerylonidae and Bothrideridae. Biphyllidae and Byturidae were recovered in Cleroidea. The remaining Cucujoidea were recovered in two disparate major clades: one comprising the nitidulid series + erotylid series + Boganiidae and Hobartiidae + cucujid series, and the other comprising the cerylonid series. Propalticidae are recovered within Laemophloeidae. The cerylonid series includes two major clades, the bothriderid group and the coccinellid group. Akalyptoischiidae are recovered as a separate clade from Latridiidae. Eupsilobiinae are recovered as the sister taxon to Coccinellidae. In light of these findings, many formal changes to cucujiform beetle classification are proposed. Biphyllidae and Byturidae are transferred to Cleroidea. The cerylonid series is formally recognized as a new superfamily, Coccinelloidea stat.n. Current subfamilies elevated (or re‐elevated) to family status include: Murmidiidae stat.n., Teredidae stat.n., Euxestidae stat.n., Anamorphidae stat.rev., Eupsilobiidae stat.n., and Mycetaeidae stat.n. The following taxa are redefined and characterized: Cleroidea s.n., Cucujoidea s.n., Cerylonidae s.n., Bothrideridae s.n., Endomychidae s.n. A new subfamily, Cyclotominae stat.n., is described. Stenotarsinae syn.n. is formally subsumed within a new concept of Endomychinae s.n.

A molecular phylogenetic analysis of the pleasing fungus beetles (Coleoptera: Erotylidae): evolution of colour patterns, gregariousness and mycophagy

Abstract.  Phylogenetic relationships of Erotylidae (pleasing fungus beetles) were inferred based on DNA sequence data. Relationships of clades within Erotylidae were examined, as was the relationship of the entire family to Languriidae (lizard beetles). 18S and 28S ribosomal DNA were sequenced for sixty‐one taxa representing major erotylid lineages and outgroups. Phylogenetic analyses under varying parameter settings using standard parsimony and likelihood techniques were performed. These data indicate a paraphyletic Erotylidae and Languriidae. Encaustinae (including Coptengis), Megalodacninae and Erotylinae are supported as monophyletic, whereas Dacninae and Tritominae are paraphyletic. Taxonomic and biological implications are discussed. Gregariousness has arisen at least three times in Erotylidae. The erotylid clade has experienced at least one evolutionary transition from mycophagy (on Aphyllophorales) to phytophagy, three transitions from Aphyllophorales hosts to Euagarics, and one transition from Euagarics hosts to Mucorales (Zygomycetes). There are no recognizable phylogenetic trends in coloration across higher‐level erotylid lineages.

Native, insect herbivore communities derive a significant proportion of their carbon from a widespread invader of forest understories.

Research on natural enemies demonstrates the potential for exotic plants to be integrated into foodwebs through the activities of native herbivores. The quantitative importance of exotics as a food resource to herbivores is more difficult to ascertain. In addition, some widespread invaders appear to have minimal herbivore loads. Microstegium vimineum is one example. It is an annual, C4 grass that invades forest understories and is widespread across the eastern US. Its invasion alters the structure and composition of forests. We sampled invertebrates in a tree-canopy gap and under canopy area, and used the unique carbon isotope value of M. vimineum to estimate the quantitative importance of the invader as a food resource relative to native plants. Seven of the eight invertebrate species derived on average >35% of their biomass carbon from M. vimineum, and some individuals representing both ‘chewing’ and ‘sucking’ feeding guilds derived their biomass carbon exclusively from M. vimineum. Our results show that M. vimineum can be a significant food resource for a multi-species, multi-guild, assemblage of native, invertebrate herbivores. Future work is required to assess whether M. vimineum is acquiring herbivores in other parts of its introduced range, and if so what might be the ecological consequences.

The association of multiple sap beetle species (Coleoptera: Nitidulidae) with western honey bee (Apis mellifera) colonies in North America

James D. Ellis, Keith S. Delaplane, Andrew Cline and Joseph V. McHugh. Department of Entomology and Nematology, University of Florida, Bldg 970 Natural Area Dr., PO Box 110620, Gainesville, FL 32601, USA. Department of Entomology, Biological Sciences Building, University of Georgia, Athens, GA 30602, USA. California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832-1448, USA.

Phylogenetic analysis of the minute brown scavenger beetles (Coleoptera: Latridiidae), and recognition of a new beetle family, Akalyptoischiidae fam.n. (Coleoptera: Cucujoidea)

We infer the first phylogenetic hypothesis for Latridiidae Erichson (Coleoptera: Cucujoidea). Portions of seven genes (18S ribosomal DNA, 28S ribosomal DNA, 12S ribosomal DNA, 16S ribosomal DNA, cytochrome c oxidase I and II and histone III) were analysed. Twenty‐seven latridiid species were included, representing both subfamilies and more than half of the currently recognized genera. Eight outgroup taxa from other families of Cucujoidea were included. Parsimony and partitioned Bayesian analyses were performed on the combined dataset. In both phylogenetic analyses, the enigmatic Akalyptoischion Andrews (Latridiinae) was recovered outside of Latridiidae. The subfamilies Corticariinae and Latridiinae (without Akalyptoischion) were each recovered as monophyletic in both analyses. A new family, Akalyptoischiidae fam.n. is erected based on the results of the phylogenetic study and further support from adult morphology, key features of which are illustrated.