The following is an overview of major projects in the McKenna lab (updated July, 2022).
Integrating phylogeny with comparative & functional genomic data to reconstruct the evolution of specialized plant-feeding in beetles
Beetles evolved a diversity of specialized plant-feeding habits following the acquisition (via HGT) of bacterial and fungal genes enabling symbiont-independent metabolism of lignocellulose in plant cell walls (McKenna et al. 2019 PNAS). These feeding habits included chewing, mining, galling, and boring of virtually all kinds and parts of living, dead, or decomposing plants. We are integrating functional and comparative genomic data in a phylogenomic framework to study the evolution of phytophagy in beetles. Our work is focused on leaf, longhorn and weevil beetles (aka Phytophaga), an enormous clade (more than 130,000 described species) of tremendous ecological and economic importance, most of which feed on plants or fungi. We are also studying metallic woodboring beetles (Buprestoidea; more than 15,000 described species). Buprestoidea are also specialized herbivores. We seek to answer enduring questions about how and when phytophagy evolved, and to evaluate the roles of symbionts and genes encoding plant cell wall degrading enzymes in the evolution of specialized plant-feeding habits in these lineages.
Characterizing the morphology & diversity of antennal sensilla in longhorn beetles to facilitate comparative & functional studies
Dr. Stephanie Haddad is interested in characterizing and comparing the morphology and diversity of antennal chemosensilla across longhorn beetles. The lack of a unified naming system for insect sensilla has hampered progress in understanding insect chemosensory biology and evolution. Studies often use different terminology and criteria in naming and identifying sensilla, making it difficult to compare the morphology and diversity of these sensory structures even across closely related insect species. In order to establish a baseline for comparison of chemosensory sensilla across longhorn beetles, she is reviewing published studies on longhorn beetle antennal sensilla to establish a unified classification system for them. This will facilitate the development and testing of hypotheses about the evolution and function of these chemosensory structures as part of a 5-year multidisciplinary collaboration funded by NSF (project description below). In addition to this work, Dr. Haddad is also conducting a comparative morphological study of antennal tufts (dense clusters of hairs) across longhorn beetles using scanning electron microscopy. The function of these tufts is unknown and their morphology is undescribed. Given the critical role of antennae in longhorn beetle biology, characterizing these antennal tufts (and their underlying sensilla) may shed light on longhorn beetle taxonomy, evolution, and behavior. Image credit: Thai National Parks, used with permission.
Reconstructing the phylogeny & evolution of beetles (order Coleoptera) with a particular focus on supra-familial relationships & macroevolution
We are reconstructing the phylogeny and evolution of beetles—including timing and patterns of diversification—using molecular, temporal, and morphological data. Most recent studies have involved generating and analyzing large phylogenomic data sets obtained via target enrichment (anchored hybrid enrichment, or ultraconserved elements), genomic meta-characters (e.g., near intron pairs, gene order), and other data obtained from genomes and transcriptomes. Recently, as part of the 1KITE Beetles Project (see paper), we sampled 146 taxa for more than 6,000 genes. The ML phylogenetic tree resulting from analysis of these data has maximal support for nearly all nodes, including (for the first time) all nodes representing supra-familial groups of beetles. Ongoing work seeks to further resolve problematic nodes within major groups of beetles, and to inrease taxon sampling at the subfamily-level within beetle families.
Investigating chemosensory evolution in longhorned beetles using a comparative phylogenomic framework that integrates genomic, morphological, & biochemical data
Drs. McKenna, Haddad, and collaborator Mitchell (Univ. WI, Oshkosh) are leading a 5-year multidisciplinary collaboration funded by NSF, to study the evolution of chemosensation and chemically-mediated ecological interactions (e.g., involving host plant- and mate-finding) in longhorn beetles (family Cerambycidae sensu lato). Their integrative approach combines phylogeny, morphology, genetics, and biochemistry in a comparative framework to address longstanding questions about how ecological factors have shaped longhorn beetle chemosensory systems over evolutionary time, and to investigate the role of chemosensation in promoting longhorn beetle diversification.
Reconstructing 50 million years of evolution along the Antarctic Polar Front: Ectemnorhinini weevils (Curculionidae: Entiminae) on the Subantarctic islands
While climate cooling and glacial-interglacial cycles have driven much of Antarctica’s former flora and fauna to extinction, they have been key to the diversification of Ectemnorhinini weevils—one of the world’s most geographically-isolated groups of insects. Drs. McKenna, Shin, and Adams have been studying the phylogeny and evolution of Ectemnorhinini with Steven Chown (Monash Univ., Australia), Helena Baird (postdoc, Chown lab, Monash Univ.), Rolf Oberprieler (CSIRO, Australia), and several other colleagues. This research has relevance to climate change, diversification paradigms involving the Antarctic biota, and the evolution of specialized herbivory. Their recent PNAS paper (video summary) provides a summary of their work. This resesarch is funded in-part by the US National Science Foundation through the 1K Weevils Project. Photo: D. Jennings (CSIRO).
Ecological & genomic forces maintaining naturally-occurring color polymorphism in the tortoise beetle Chelymorpha alternans (Chrysomelidae: Cassidinae)
NSF postdoctoral fellow Dr. Lynette Strickland is investigating genetic variation, sequestration of plant secondary metabolites, larval survivorship, and adult palatability in the polymorphic Neotropical tortoise beetle, Chelymorpha alternans, which is associated with plants in the family Convolvulaceae. Elucidating how individual genetic variation affects sequestration ability and susceptibility to predation is essential to understanding the community composition and spatial distributions of toxin-producing plant hosts, sequestering herbivores, and their predators. The field component of Lynette's research is based in Panama with collaborators at the Smithsonian Tropical Research Institute. In addition to wet lab (genetic/genomic) and field studies, Lynette plans to undertake experiments with captive live beetles and host plants in a climate-controlled quarantine facility at the University of Memphis.
Cryptic speciation, endemism & host plant associations of Neotropical ‘hispine’ beetles (Chrysomelidae: Cassidinae) in the genera Chelobasis & Cephaloleia
Dr. Duane McKenna is studying Neotropical leaf beetles in the tribes Cephaloleiini and Arescini (Chrysomelidae: Cassidinae) that feed on plants in the order Zingiberales. This work builds on his previously published studies of these beetles in Mesoamerica. His current interests include documentating geographic distributions, host plant associations, and cryptic species of Cephaloleiini and Aescini. Data collected to date has shown that populations of most species residing in lowland tropical wet and humind forests on and near the Osa Peninsula in Costa Rica show variation in host plant taxa and host specificity compared to populations on the Caribbean slope of Mesoamerica (which tend to be more specialized), from which they are geographically-isolated by high mountains. Molecular and morphological data are consistent with recognition of these isolated populations of beetles as different species. Moreover, his studies show that these populations have been evolving seperately for millennia.
Island biogeography in the continental Neotropics: Reconstructing the phylogeny & evolution of Mesoamerican bess beetles (Passalidae)
The insect fauna of Mesoamerica exhibits a high degree of local, regional and high-elevation endemism—patterns exemplified by bess beetles (Passalidae) in the tribe Proculini. The species diversity of Proculini is concentrated in Mesoamerican montane forests, but the historical biogeography and evolutionary origins of Neotropical Proculini remain poorly-known. Dr. Cristian Beza-Beza is studying the geographic distributions of Proculini species, as well as timing and patterns of Proculini diversification. He seeks to test theories about the origins of tropical forest insect diversity and contribute to the development of strategies for its conservation. His studies involve collaborators, fieldwork, and museum collections throughout the Neotropics, coupled with studies of Proculini morphology, molecular phylogenetics, and evolution. He recently published a paper summarizing notable results from this work, and is now extending his studies into South America in collaboration with Dr. Larry Jimenez-Ferbans (Univer. del Magdalena, Colombia).
Gene, gene family, & genome evolution in insects, with a focus on the Neuropteroidea (Neuropterida, Strepsiptera, & Coleoptera)
Dr. Duane McKenna led the Asian longhorn beetle (Anoplophora glabripennis; ALB) genome project and has been involved in several additional beetle genome projects, including the emerald ashborer (Agrilus planipennis), bull-headed dung beetle (Onthophagus taurus), and small hive beetle (Aethina tumida). Some of these genomes were sequenced and assembled as part of the insect 5,000 genomes pilot project (i5k). In 2019, a chromosome-scale ALB genome assembly was completed in collaboration with Dovetail Genomics (contact Duane McKenna for more information). The McKenna lab has sequenced and assembled several additional beetle genomes, including exemplars from suborders Archostemata and Myxophaga, which currently lack publicly-available whole genome sequences (a partial Archostemata [Priacma serratta] genome was published in our Strepsiptera genome paper in 2012). An i5k pilot project summary paper that includes analyses of data from more than 70 arthropod genomes, was published in 2020.
Host associations & conservation status of Curculio weevil species associated with American chestnut (Castanea dentata) in North America
PhD student Michael Charles is studying the phylogeny and evolution of Curculio (Curculionidae: Curculioninae) and the ecological interactions between Curculio species and their host plants in Eastern North America. He is also studying the biology and distribution of the greater and lesser chestnut weevils (both in the genus Curculio), as well as their apparent differing degrees of host-plant specificity. Photo courtesy of Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org.
1000 Curculionidae Phylogeny & Evolution Project (1K Weevils)
Most weevil species belong to the family Curculionidae Latreille (~51,000 species; 4,600 genera), the second largest family of metazoans. Diversification of Curculionidae started in the Cretaceous Period as flowering plants first rose to widespread floristic dominance (McKenna et al. 2009, PNAS). However, relationships, and timing and patterns of diversification within Curculionidae remain virtually unknown. We are using target enrichment to obtain DNA sequences from more than 500 genes for more than 1,000 genera of weevils. This project involves collaborators working on all continents (including Antarctica! See our research on Ectemnorhinini, above, for more information). Data collection for this project is complete.
Cretaceous Burmese Amber Weevils
Drs. Dave Clarke (University of Memphis), and Rolf Oberprieler (CSIRO, Australia) are studying early Upper Cretaceous fossil weevils preserved in Burmese amber. Their work is focused on the extinct family Mesophyletidae. Recently, they published a comprehensive revision of Burmese amber weevil fauna: The weevil fauna preserved in Burmese amber – snapshot of a unique, extinct lineage (Coleoptera: Curculionoidea) along with Drs. McKenna and Ajay Limaye (Australian National University).
A multidisciplinary approach to studying bioacoustics: Integrating phylogenomics, biophysics, & functional genomics to unravel the evolution of hearing & singing in katydids, crickets, & relatives
Insects are the most diverse group of animals on Earth that communicate acoustically, even outnumbering the many mammal and bird species that use this mode of communication. The insect order Orthoptera contains approximately 16,000 species which use acoustic communication. However, unlike mammals and birds, they use various specialized mechanisms on their wings or legs and abdomens, to create and hear sounds. Drs. McKenna and Shin are collaborating with Dr. Hojun Song (project PI) on a recently awarded 5-year NSF grant seeking to further characterize the evolution of hearing and singing in Ensifera, a suborder of Orthoptera which contains katydids, crickets, and allied taxa.
Phylogeny & evolution of the longhorn beetle family Dorcasominae (Coleoptera: Cerambycidae) with a particular focus on the fauna of Madagascar
Ph.D. student Soohyun Jeong is reconstructing the phylogeny, evolutionary history, and biogeographic distribution of the longhorn beetle subfamily Dorcasominae. Dorcasominae are an early-divergent lineage of subfamily Cerambycinae. While Dorcasominae are widely distributed elsewhere across the Southern Hemisphere, most known species (>300) are endemic to Madagascar. Photo credit: Ben Sale from UK, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
Leveraging population genomics & statistical frameworks to reveal the evolutionary mechanisms that drive genomic innovation in an invasive beetle species
In partnership with Dr. Rich Adams (Asst. Professor, Georgia College) we are studying the evolutionary processes that drive rapid adaptation in the invasive citrus root weevil, Diaprepres abbreviatus. We will use whole genome resequencing and statistical frameworks to evaluate the role of demographic factors and human-mediated spread in promoting adaptation, develop statistical methods for testing genomic outliers and evidence of selection, investigate the evolution of gene families that are key to successful herbivory, evaluate the roles of pre- vs. post-invasion processes, and develop new approaches for genomic prediction to study ancestry and adaptation. We are planning similar work with the emerald ash borer (Agrilus planipennis) and several additional plant-feeding beetle species. Broadly, this research will reveal key drivers of adaptation underlying colonization of new host plants and environments, as well as fundamental principles of population and invasion genomics. Photo credit: Keith Weller, USDA Agricultural Research Service, Bugwood.org