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This chapter introduces the basic approaches to systematics—using morphological and molecular data—and it considers the history of systematic analysis in odonates. In this chapter we address how different molecular methods have been applied at different times to the study of odonate systematics. We also review the current understanding of relationships within the three main suborders (Zygoptera, Anisozygoptera and Anipoptera) and highlight areas in need of further research. We then look at how systematics tools can be applied to address questions in ecology and evolution, consider some questions that systematics cannot answer, and review the future of odonate systematic research.

Here, we investigate the evolutionary history of five northern dragonfly species to evaluate what role the last glaciation period may have played in their current distributions. We look at the population structure and estimate divergence times for populations of the following species: Aeshna juncea (Linnaeus), Aeshna subarctica Walker, Sympetrum danae (Sulzer), Libellula quadrimaculata Linnaeus and Somatochlora sahlbergi Trybom across their Holarctic range. Our results suggest a common phylogeographic pattern across all species except for S. sahlbergi. First, we find that North American and European populations are genetically distinct and have perhaps been separated for more than 400,000 years. Second, our data suggests that, based on genetics, populations from the Greater Beringian region (Beringia, Japan and China) have haplotypes that cluster with North America or Europe depending on the species rather than having a shared geographic affinity. This is perhaps a result of fluctuating sea levels and ice sheet coverage during the Quaternary period that influenced dispersal routes and refugia. Indeed, glacial Beringia may have been as much a transit zone as a refugia for dragonflies. Somatochlora sahlbergi shows no genetic variation across its range and therefore does not share the geographic patterns found in the other circumboreal dragonflies studied here. Lastly, we discuss the taxonomic status of Sympetrum danae, which our results indicate is a species complex comprising two species, one found in Eurasia through Beringia, and the other in North America east and south of Beringia. Through this study we present a shared history among different species from different families of dragonflies, which are influenced by the climatic fluctuations of the past. Copyright 2021 Kohli et al. Funsing: Manpreet Kohli received funding from the Systematic Research Fund, 2017 funded by Linnaean Society of London. Manpreet Kohli also received funds from Theodore Roosevelt Memorial Fund, 2017 funded American Museum of Natural History. Thomas J Simonsen, Marie Djernæs and Kent Olsen received funding from the research fund under the Danish Ministry for Culture (grant: FORM.2015-0023), 15 June Foundation (grant: 2015-A-89), The SYNTHESYS program under the EU Commission (grant: SE-TAF-5543). Jessica Ware received funding from National Science Foundation grant #1564386.

International audience; Phylogenomics seeks to use next‐generation data to robustly infer an organism's evolutionary history. Yet, the practical caveats of phylogenomics motivate investigation of improved efficiency, particularly when quality of phylogenies are questionable. To achieve improvements, one goal is to maintain or enhance the quality of phylogenetic inference while severely reducing dataset size. We approach this by assessing which kinds of loci in phylogenomic alignments provide the majority of support for a phylogenetic inference of cockroaches in Blaberoidea. We examine locus substitution rate, saturation, evolutionary divergence, rate heterogeneity, stabilizing selection, and a priori information content as traits that may determine optimality. Our controlled experimental design is based on 265 loci for 102 blaberoidean taxa and 22 outgroup species. Loci with high substitution rate, low saturation, low sequence distance, low rate heterogeneity, and strong stabilizing selection derive more support for phylogenetic relationships. We found that some phylogenetic information content estimators may not be meaningful for assessing information content a priori. We use these findings to design concatenated datasets with an optimized subsample of 100 loci. The tree inferred from the optimized subsample alignment was largely identical to that inferred from all 265 loci but with less evidence of long branch attraction, improved statistical support, and potential 4‐6x improvements to computation time. Supported by phylogenetic and morphological evidence, we erect three newly named clades (Anallactinae Evangelista & Wipfler subfam. nov., Orkrasomeria tax. nov. Evangelista, Wipfler, & Béthoux and Hemithyrsocerini Evangelista tribe nov.) and propose other taxonomic modifications. The diagnosis of Pseudophyllodromiidae Grandcolas, 1996 is modified to accommodate Anallactinae and Pseudophyllodromiinae Vickery & Kevan, 1983. The diagnosis of Ectobiidae Brunner von Wattenwyl, 1865 is modified to add novel morphological characters.

SummaryDragonflies and damselflies, representing the insect order Odonata, are among the earliest flying insects with living (extant) representatives. However, unravelling details of their long evolutionary history, such as egg laying (oviposition) strategies, is impeded by unresolved phylogenetic relationships, an issue particularly prevalent in damselfly families and fossil lineages. Here we present the first transcriptome-based phylogenetic reconstruction of Odonata, analyzing 2,980 protein-coding genes in 105 species representing nearly all of the order’s families (except Austropetaliidae and Neopetaliidae). All damselfly families and most dragonfly families are recovered as monophyletic groups. Our Molecular clock estimates suggest that crown-Zygoptera (damselflies) and -Anisoptera (dragonflies) both arose during the late Triassic. Several of the observed long inner branches in our topology are indicative of the extinction of once flourishing lineages. We also find that exophytic egg laying behaviour with a reduced ovipositor evolved in certain dragonflies during the late Jurassic / early Cretaceous. Lastly, we find that certain fossils have an unexpected deterring impact in divergence dating analysis.

Summary Dragonflies and damselflies are among the earliest flying insects with extant representatives. However, unraveling details of their long evolutionary history, such as egg laying (oviposition) strategies, is impeded by unresolved phylogenetic relationships, particularly in damselflies. Here we present a transcriptome-based phylogenetic reconstruction of Odonata, analyzing 2,980 protein-coding genes in 105 species representing nearly all the order’s families. All damselfly and most dragonfly families are recovered as monophyletic. Our data suggest a sister relationship between dragonfly families of Gomphidae and Petaluridae. According to our divergence time estimates, both crown-Zygoptera and -Anisoptera arose during the late Triassic. Egg-laying with a reduced ovipositor apparently evolved in dragonflies during the late Jurassic/early Cretaceous. Lastly, we also test the impact of fossil choice and placement, particularly, of the extinct fossil species, †Triassolestodes asiaticus, and †Proterogomphus renateae on divergence time estimates. We find placement of †Proterogomphus renateae to be much more impactful than †Triassolestodes asiaticus., Graphical abstract, Highlights • Relationships of dragonflies and damselflies are unraveled using transcriptomes • Earliest flying insects – Odonata and extinct relatives – date back to Permian period • Both extant dragonflies and damselflies started diverging in the Triassic period, Evolutionary biology; Phylogenetics

Phylogenomics seeks to use next-generation data to robustly infer an organism’s evolutionary history. Yet, the practical caveats of phylogenomics motivates investigation of improved efficiency, particularly when quality of phylogenies are questionable. To achieve improvements, one goal is to maintain or enhance the quality of phylogenetic inference while severely reducing dataset size. We approach this goal by designing an optimized subsample of data with an experimental design whose results are determined on the basis of phylogenetic synecdoche − a comparison of phylogenies inferred from a subsample to phylogenies inferred from the entire dataset. We examine locus mutation rate, saturation, evolutionary divergence, rate heterogeneity, selection, and a priori information content as traits that may determine optimality. Our controlled experimental design is based on 265 loci for 102 blaberoidean cockroaches and 22 outgroup species. High phylogenetic utility is demonstrated by loci with high mutation rate, low saturation, low sequence distance, low rate heterogeneity, and low selection. We found that some phylogenetic information content estimators may not be meaningful for assessing information content a priori. We use these findings to design concatenated datasets with an optimized subsample of 100 loci. The tree inferred from the optimized subsample alignment was largely identical to that inferred from all 265 loci but with less evidence of long branch attraction and improved statistical support. In sum, optimized subsampling can improve tree quality while reducing data collection costs and yielding 4-6x improvements to computation time in tree inference and bootstrapping.

Phylogenetic relationships among subgroups of cockroaches and termites are still matters of debate. Their divergence times and major phenotypic transitions during evolution are also not yet settled. We addressed these points by combining the first nuclear phylogenomic study of termites and cockroaches with a thorough approach to divergence time analysis, identification of endosymbionts, and reconstruction of ancestral morphological traits and behaviour. Analyses of the phylogenetic relationships within Blattodea robustly confirm previously uncertain hypotheses such as the sister-group relationship between Blaberoidea and remaining Blattodea, and Lamproblatta being the closest relative to the social and wood-feeding Cryptocercus and termites. Consequently, we propose new names for various clades in Blattodea: Cryptocercus + termites = Tutricablattae; Lamproblattidae + Tutricablattae = Kittrickea; and Blattoidea + Corydioidea = Solumblattodea. Our inferred divergence times contradict previous studies by showing that most subgroups of Blattodea evolved in the Cretaceous, reducing the gap between molecular estimates of divergence times and the fossil record. On a phenotypic level, the blattodean ground-plan is for egg packages to be laid directly in a hole while other forms of oviposition, including ovovivipary and vivipary, arose later. Finally, other changes in egg care strategy may have allowed for the adaptation of nest building and other novelties.

Phylogenetic relationships among subgroups of cockroaches and termites are still matters of debate. Their divergence times and major phenotypic transitions during evolution are also not yet settled. We addressed these points by combining the first nuclear phylogenomic study of termites and cockroaches with a thorough approach to divergence time analysis, identification of endosymbionts, and reconstruction of ancestral morphological traits and behaviour. Analyses of the phylogenetic relationships within Blattodea robustly confirm previously uncertain hypotheses such as the sister-group relationship between Blaberoidea and remaining Blattodea, and Lamproblatta being the closest relative to the social and wood-feeding Cryptocercus and termites. Consequently, we propose new names for various clades in Blattodea: Cryptocercus + termites = Tutricablattae; Lamproblattidae + Tutricablattae = Kittrickea; and Blattoidea + Corydioidea = Solumblattodea. Our inferred divergence times contradict previous studies by showing that most subgroups of Blattodea evolved in the Cretaceous, reducing the gap between molecular estimates of divergence times and the fossil record. On a phenotypic level, the blattodean ground-plan is for egg packages to be laid directly in a hole while other forms of oviposition, including ovovivipary and vivipary, arose later. Finally, other changes in egg care strategy may have allowed for the adaptation of nest building and other novelties.

We present the first empirical treatment of the northernmost breeding dragonfly, Somatochlora sahlbergi. We sequenced populations from United States, Canada, Finland, Sweden and Norway for cytochrome oxidase I (COI) and D2 region of 28s. We found that, despite geographic barriers across its vast arctic range, S. sahlbergi is a single species. Not only does it appear to interbreed across its entire range, there also seems to be almost no variation among European and North American populations in their COI gene fragment (the barcode gene), which is usually extremely variable. We further found that characters thought to be diagnostic for the larvae of S. sahlbergi were absent in our European samples. We review and re-describe the habitat of this species based on new findings from recent field observations. Finally, we report for the first time the likely presence of this species in Japan. We hope our findings will encourage further study of this species and other under-studied insect taxa that inhabit the remote Arctic.

Boyeria irene and Boyeria cretensis are species of spotted dragonflies belonging to the ‘darner’ family, Aeshnidae. In 1991, Peters classified Boyeria from Crete as B. cretensis, based on adult morphological characters. In this study, we used molecular evidence to determine if indeed B. irene and B. cretensis are different species. DNA was sequenced from samples of B. irene (from France, Switzerland, Tunisia, Spain and Italy) and B. cretensis (from Crete). These species were recovered as two different clades with strong support. We conclude that B. irene and B. cretensis are different species, with evidence based on molecular and morphological differences. In addition, we present the first phylogenetic hypothesis for Boyeria for which we have sequenced all but three species. Lastly, we discuss different scenarios that may have led to the present-day distribution and speciation patterns of Mediterranean Boyeria.

Molecular data along with fossils are being used increasingly to recover time-calibrated phylogenetic trees. Recently there have been manuscripts that have used divergence dating to understand evolutionary history of certain clades within Odonata (dragonflies and damselflies), yet the number of such articles is still low. We examined the Odonata fossil record and made a list of fossils that can be used for divergence time analysis. In this manuscript we provide a detailed review of the known crown group fossils for the order Odonata and nine nodes within this clade: Zygoptera, Epiprocta, Anisoptera, Aeshnidae, Gomphidae, Cavilabiata, Macromiidae, Corduliidae, and Libellulidae. Manpreet Kaur Kohli. Rutgers University, 195 University Ave, Newark, NJ 07102, USA. mkk24@njit.edu Jessica L. Ware. Rutgers University, 195 University Ave, Newark, NJ 07102, USA. jware@amnh.org Gunter Bechly. Department of Paleontology, State Museum of Natural History, Rosenstein 1, 70191 Stuttgart, Germany. guenter.bechly@smns-bw.de (corresponding author)

Fossils provide the principal basis for temporal calibrations, which are critical to the accuracy of divergence dating analyses. Translating fossil data into minimum and maximum bounds for calibrations is the most important, and often least appreciated, step of divergence dating. Properly justified calibrations require the synthesis of phylogenetic, paleontological, and geological evidence and can be difficult for non- specialists to formulate. The dynamic nature of the fossil record (e.g., new discoveries, taxonomic revisions, updates of global or local stratigraphy) requires that calibration data be updated continually lest they become obsolete. Here, we announce the Fossil Calibration Database (http://fossilcalibrations.org), a new open- access resource providing vetted fossil calibrations to the scientific community. Calibrations accessioned into this database are based on individual fossil specimens and follow best practices for phylogenetic justification and geochronological constraint. The associated Fossil Calibration Series, a calibration-themed publication series at Palaeontologia Electronica, will serve as one key pipeline for peer-reviewed calibrations to enter the database.