Chromosome-Aware Phylogenomics of Assassin Bugs (Hemiptera: Reduvioidea) Elucidates Ancient Gene Conflict.

Though the phylogenetic signal of loci on sex chromosomes can differ from those on autosomes, chromosomal-level genome assemblies for nonvertebrates are still relatively scarce and conservation of chromosomal gene content across deep phylogenetic scales has therefore remained largely unexplored. We here assemble a uniquely large and diverse set of samples (17 anchored hybrid enrichment, 24 RNA-seq, and 70 whole-genome sequencing samples of variable depth) for the medically important assassin bugs (Reduvioidea). We assess the performance of genes based on multiple features (e.g., nucleotide vs. amino acid, nuclear vs. mitochondrial, and autosomal vs. X chromosomal) and employ different methods (concatenation and coalescence analyses) to reconstruct the unresolved phylogeny of this diverse (∼7,000 spp.) and old (>180 Ma) group. Our results show that genes on the X chromosome are more likely to have discordant phylogenies than those on autosomes. We find that the X chromosome conflict is driven by high gene substitution rates that impact the accuracy of phylogenetic inference. However, gene tree clustering showed strong conflict even after discounting variable third codon positions. Alternative topologies were not particularly enriched for sex chromosome loci, but spread across the genome. We conclude that binning genes to autosomal or sex chromosomes may result in a more accurate picture of the complex evolutionary history of a clade.

Phylogenetic relationships and revised classification of the true bug infraorder Dipsocoromorpha (Insecta: Hemiptera: Heteroptera).

Currently comprising only about 430 species, Dipsocoromorpha or minute litter bugs are one of the small infraorders of Heteroptera. They are classified into five morphologically distinct families--Ceratocombidae, Dipsocoridae, Hypsipterygidae, Schizopteridae and Stemmocryptidae--but relationships among and within these families are poorly understood owing to the lack of phylogenetic studies. A phylogenetic hypothesis based on combined molecular and morphological data is important to both evaluate and revise the higher-level classification and to explore the evolutionary history of morphological features including elytriform (or beetle-like) forewings, that seem to have evolved multiple times in this group, jumping devices, and the highly modified and diverse male genitalia. We here use a dataset combining Sanger-derived (~4500 bp; 108 taxa) and Illumina-generated (~7500 bp; 24 taxa) sequence data with a morphological matrix (159 characters) and taxon sampling that comprises all currently recognized family-, subfamily- and tribal-level taxa and comprehensive genus-level sampling to investigate phylogenetic relationships within litter bugs. Our results support the monophyly of Dipsocoromorpha, Schizopteridae and Dipsocoridae, whereas Ceratocombidae and the schizopterine subfamily "Ogeriinae" are polyphyletic and paraphyletic, respectively. A new classification is proposed that recognizes six families, including Trichotonannidae, stat.n., and two subfamilies each within the two larger families Ceratocombidae and Schizopteridae. Ancestral state reconstructions outline the complex evolutionary history of many morphological characters, including 15 independent origins of elytriform forewings, and at least five shifts in the degree of genitalic asymmetry.

Four new genera of Schizopteridae (Hemiptera: Heteroptera) from the Afrotropical and Neotropical regions.

Despite a recent surge of taxonomic work on the dipsocoromorphan family Schizopteridae, new genus-level taxa remain to be documented and described. The curation of Malaise and Yellow Pan Trap sample residues from Central and South America and Cameroon resulted in the discovery of five undescribed species that based on combined molecular and morphological phylogenetic analyses represent four phylogenetically isolated lineages within non-hypselosomatine Schizopteridae. To accommodate these new species, we here describe the four new genera Caucanannus gen. n. (Colombia, Ecuador, and Brazil) with Caucanannus perplexus sp. n. and Caucanannus novissimis sp. n.; Kamakonocoris gen. n. (Cameroon) with Kamakonocoris carinata sp. n.; Perittonannus gen. n. (Costa Rica) with Perittonannus antiquus sp. n.; and Rimanannus gen. n. (Cameroon) with Rimanannus camerunensis sp. n. The four genera are characterized by distinctive wing venation and male and female genitalic features. We provide habitus photographs and document morphological details using digital macrophotography as well as light compound microscopic and scanning electron microscopic images. Maps and measurements are also included.

Taxonomic revision of the New World big-eyed minute litter bug genus Ommatides Uhler (Hemiptera: Schizopteridae).

Hypselosomatinae, the big-eyed minute litter bugs, are diagnosed among Schizopteridae (infraorder Dipsocoromorpha) by the large eye, 4-segmented labium, and distinct wing venation. The group was recovered as sister taxon to all remaining Schizopteridae in recent molecular phylogenetic analyses. Described species diversity of Hypselosomatinae (13 extant genera prior to this study) is greatest in the Old World and in particular the Australian region, while only five monotypic or small genera are currently described from the New World (Glyptocombus Heidemann, Ommatides Uhler, Williamsocoris Carpintero Dellapé, Hypsohapsis Hoey-Chamberlain Weirauch, and Hypselosomops Hoey-Chamberlain Weirauch). Based on examination of 60 specimens of Hypselosomatinae from South America, we here synonymize Ommatides that includes one described species from the Lesser Antilles with the monotypic genus Williamsocoris Carpintero Dellapé from Argentina, describe seven new species of Ommatides (O. duodentis sp. nov., O. nudus sp. nov., O. parvidentis sp. nov., O. pillcopata sp. nov., O. pristis sp. nov., O. tridentis sp. nov., O. yoderi sp. nov. and O. zanderij sp. nov.) from various locations in South America, and redescribe Ommatides. We provide thorough documentation of morphological features using macroimages, SEM, and line drawings for new taxa and Ommatides insignis Uhler and a distribution map for all currently known New World Hypselosomatinae.

Insight from an ultraconserved element bait set designed for hemipteran phylogenetics integrated with genomic resources.

Target enrichment of conserved genomic regions facilitates collecting sequences of many orthologous loci from non-model organisms to address phylogenetic, phylogeographic, population genetic, and molecular evolution questions. Bait sets for sequence capture can simultaneously target thousands of loci, which opens new avenues of research on speciose groups. Current phylogenetic hypotheses on the >103,000 species of Hemiptera have failed to unambiguously resolve major nodes, suggesting that alternative datasets and more thorough taxon sampling may be required to resolve relationships. We use a recently designed ultraconserved element (UCE) bait set for Hemiptera, with a focus on the suborder Heteroptera, or the true bugs, to test previously proposed relationships. We present newly generated UCE data for 36 samples representing three suborders, all seven heteropteran infraorders, 23 families, and 34 genera of Hemiptera and one thysanopteran outgroup. To improve taxon sampling, we also mined additional UCE loci in silico from published hemipteran genomic and transcriptomic data. We obtained 2271 UCE loci for newly sequenced hemipteran taxa, ranging from 265 to 1696 (average 904) per sample. These were similar in number to the data mined from transcriptomes and genomes, but with fewer loci overall. The amount of missing data correlates with greater phylogenetic divergence from taxa used to design the baits. This bait set hybridizes to a wide range of hemipteran taxa and specimens of varying quality, including dried specimens as old as 1973. Our estimated phylogeny yielded topologies consistent with other studies for most nodes and was strongly-supported. We also demonstrate that UCE loci are almost exclusively from the transcribed portion of the genome, thus data can be successfully integrated with existing genomic and transcriptomic resources for more comprehensive phylogenetic sampling, an important feature in the era of phylogenomics. UCE approaches can be used by other researchers for additional studies on hemipteran evolution and other research that requires well resolved phylogenies.

Synopsis of Schizopteridae (Hemiptera, Heteroptera, Dipsocoromorpha) from the United States, with description of seven new species from the US and Mexico.

Because species diversity of the small true bug family Schizopteridae is greatest in tropical and subtropical areas, it is not surprising that only four species have been described from the United States. As part of a larger project on the taxonomy and phylogenetics of Schizopteridae, 178 specimens from the United States were examined. This material contained representatives of the previously described species Glyptocombussaltator Heidemann, 1906, Corixideamajor McAtee & Malloch, 1925, Nannocorisarenarius Blatchley, 1926, and Schizopterabispina McAtee & Malloch, 1925, but also six undescribed species. These new taxa are described as Glyptocombushalbertae sp. n., Glyptocombussuteri sp. n., Nannocorisanophorus sp. n., Nannocorisbrevipilus sp. n., Schizoptera (Cantharocoris) rileyisp. n., and Schizoptera (Schizoptera) henryisp. n. Habitus images and genitalic illustrations of the previously described and the new species are provided as well as a map showing distribution ranges of these species in the United States and Mexico. To provide a comprehensive treatment of the small genus Glyptocombus Heidemann, 1906, Glyptocombusmexicanus sp. n. is also described that, to our knowledge, occurs only in Mexico, and the female of one additional undescribed Glyptocombus species is documented from Mexico.

Comparative morphology of male genitalic structures in the minute litter bugs Dipsocoromorpha (Insecta: Hemiptera: Heteroptera).

Insect male genitalia show an evolutionarily variable morphology that has proven to be valuable for both, species identifications and phylogenetic analyses at higher taxonomic levels. Accurate usage of genitalic characters in taxonomic descriptions and phylogenetic analyses depends on consistency of terminology and validity of homology hypotheses. Both areas are underdeveloped in many insect groups. We here document the morphology and advance homology hypotheses of male genitalic features for the hemipteran infraorder Dipsocoromorpha, the minute litter bugs. Genitalic structures and the pregenital abdomen in Dipsocoromorpha are strikingly modified and diverse compared to other Heteroptera. In addition to variation in the shape of phallic structures (parameres and aedeagus), minute litter bug genitalia vary in the direction and degree of asymmetry and feature a plethora of processes derived from various abdominal segments with significant variation at low taxonomic levels. Here, male genitalic structures for an extensive taxonomic sample (32 genera and 71 specimens) are documented using scanning electron and confocal microscopy, and a universal terminology for genitalic structures across minute litter bugs is established that will facilitate species discovery and evolutionary research. We conclude by proposing primary homology hypotheses across the infraorder that now can be tested in a phylogenetic framework.

Giant among dwarfs: Meganannus lewisi, gen. n. and sp. n., a new genus and species of minute litter bugs from Costa Rica (Hemiptera: Schizopteridae).

The Neotropical biodiversity of the cryptic and tiny minute litter bugs in the family Schizopteridae-although thought to be the best documented tropical fauna of Schizopteridae-is still poorly known. Sixteen species of Schizopteridae have been described from Costa Rica, 13 of which during the past few years, and the last new genus of Schizopteridae from that country was described more than half a century ago. We here describe and document a new monotypic genus of Schizopteridae from Costa Rica, Meganannus n. gen. The new genus belongs to the "Ogeriinae" + Schizopterinae lineage of Schizopteridae and stands out among other litter bugs by the large body size, among other features. We provide habitus photographs and document morphological details using scanning electron, confocal, and light compound microscopic images. A map and measurements are also produced. An illustrated identification key to genus groups and/or genera of Neotropical Schizopteridae including this new genus is presented.

Two new genera of big-eyed minute litter bugs (Hemiptera, Schizopteridae, Hypselosomatinae) from Brazil and the Caribbean.

Charismatic Hypselosomatinae (currently 14 extant and fossil genera; 72 species), the "big-eyed minute litter bugs", are characterized among Schizopteridae (Dipsocoromorpha) by the large eyes, four-segmented labium, and distinctive wing venation. A recent molecular phylogenetic analysis confirmed the monophyly of Hypselosomatinae that were recovered as the sister taxon to the Ogeriinae + Schizopterinae (Weirauch and Stys 2014). Hypselosomatinae occur in the Old and New Worlds, but described species diversity is biased towards the Oriental and Australian regions: only three monotypic genera are currently known from the New World (Glyptocombus Heidemann, Ommatides Uhler, and Williamsocoris Carpintero & Dellapé). Based on 28 male, female, and juvenile specimens from Cuba and the Dominican Republic and a single male specimen from Brazil we here describe two new monotypic genera of Hypselosomatinae, Hypselosomops peckigen. n. and sp. n., and Hypsohapsis takiyaegen. n. and sp. n. We provide habitus images, digital illustrations (light, scanning electron, and/or confocal microscope) of wing and male genitalic structures, line drawings of genitalic structures, and distribution maps. Bizarre morphologies, a worldwide distribution with small endemic species ranges, and a fossil record that dates back to the mid-Cretaceous make the Hypselosomatinae a fascinating group to explore in an effort to understand the evolutionary history of Dipsocoromorpha.

The survivorship and water loss of Liometopum luctuosum (Hymenoptera: Formicidae) and Liometopum occidentale (Hymenoptera: Formicidae) exposed to different temperatures and relative humidity.

Two species of velvety tree ants, Liometopum luctuosum Wheeler, and Liometopum occidentale Emery (Hymenoptera: Formicidae), are commonly found in the western Unites States from Washington to southern California. L. luctuosum is restricted to coniferous forests in the mountains in the southern range, whereas L. occidentale is found in the lowlands. The survivorship of workers of both species exposed to several temperatures and relative humidity (RH) was determined. As temperature increased, survival of both species decreased. As the RH increased, survival of both species increased. However, L. luctuosum had higher overall survival in all treatment groups. The cuticular permeability (CP) and the rates of body water loss for each species were determined. Both species had similar CPs. Increased physiological tolerances of L. luctuosum may be an explanation for its broader distribution.