An integrative phylogenomic approach to elucidate the evolutionary history and divergence times of Neuropterida (Insecta: Holometabola)

The de novo genome of the Black-necked Snakefly (Venustoraphidia nigricollis Albarda, 1891): A resource to study the evolution of living fossils

Snakeflies (Raphidioptera) are the smallest order of holometabolous insects that have kept their distinct and name-giving appearance since the Mesozoic, probably since the Jurassic, and possibly even since their emergence in the Carboniferous, more than 300 million years ago. Despite their interesting nature and numerous publications on their morphology, taxonomy, systematics, and biogeography, snakeflies have never received much attention from the general public, and only a few studies were devoted to their molecular biology. Due to this lack of molecular data, it is therefore unknown, if the conserved morphological nature of these living fossils translates to conserved genomic structures. Here, we present the first genome of the species and of the entire order of Raphidioptera. The final genome assembly has a total length of 669 Mbp and reached a high continuity with an N50 of 5.07 Mbp. Further quality controls also indicate a high completeness and no meaningful contamination. The newly generated data was used in a large-scaled phylogenetic analysis of snakeflies using shared orthologous sequences. Quartet score and gene concordance analyses revealed high amounts of conflicting signals within this group that might speak for substantial incomplete lineage sorting and introgression after their presumed re-radiation after the asteroid impact 66 million years ago. Overall, this reference genome will be a door-opening dataset for many future research applications, and we demonstrated its utility in a phylogenetic analysis that provides new insights into the evolution of this group of living fossils.

Female Germline Cysts in Animals: Evolution and Function

Germline cysts are syncytia formed by incomplete cytokinesis of mitotic germline precursors (cystoblasts) in which the cystocytes are interconnected by cytoplasmic bridges, permitting the sharing of molecules and organelles. Among animals, such cysts are a nearly universal feature of spermatogenesis and are also often involved in oogenesis. Recent, elegant studies have demonstrated remarkable similarities in the oogenic cysts of mammals and insects, leading to proposals of widespread conservation of these features among animals. Unfortunately, such claims obscure the well-described diversity of female germline cysts in animals and ignore major taxa in which female germline cysts appear to be absent. In this review, I explore the phylogenetic patterns of oogenic cysts in the animal kingdom, with a focus on the hexapods as an informative example of a clade in which such cysts have been lost, regained, and modified in various ways. My aim is to build on the fascinating insights of recent comparative studies, by calling for a more nuanced view of evolutionary conservation. Female germline cysts in the Metazoa are an example of a phenomenon that-though essential for the continuance of many, diverse animal lineages-nevertheless exhibits intriguing patterns of evolutionary innovation, loss, and convergence.

Cephalic anatomy highlights morphological adaptation to underground habitats in a minute lacewing larva of Dilar (Dilaridae) and conflicting phylogenetic signal in Neuroptera

Dilaridae are a distinctive and phylogenetically ambiguous neuropteran family. So far, the anatomy of the immature stages remains largely unknown. We examined the 1st instar larvae of Dilar montanus in detail and present results of live observations for the first time. The minute, cryptic larvae display features correlated with their underground lifestyle: for instance, a strongly flattened head, stout antennae, eyelessness, and burrowing forelegs. In contrast to molecular data, several characters suggest a 'dilarid clade' combining Dilaridae with Mantispoidea, for instance a very thin and curved or reduced tentorial bridge, and an elongated postmentum. We found intrinsic antennal muscles and Johnston's organ, the first record of these structures in holometabolous larvae. This proves that the first 2 larval antennomeres are homologous with the scapus and pedicellus. The described characters are discussed and analyzed with an updated matrix of neuropteran larval characters. Alternative scenarios of character evolution are presented. Additionally, we show how the 1st-instar larvae move and feed in the substrate, and also provide a high-resolution video recording of the function of the elongate tubular ovipositor and the egg-laying behavior in an adult female under natural conditions.

The Morphological Diversity of Dragon Lacewing Larvae (Nevrorthidae, Neuroptera) Changed More over Geological Time Scales Than Anticipated

Nevrorthidae, the group of dragon lacewings, has often been considered a relic group. Today, dragon lacewings show a scattered distribution, with some species occurring in southern Europe, Japan, Australia, and one in China. The idea that this distribution is only a remnant of an originally larger distribution is further supported by fossils of the group preserved in ambers from the Baltic region (Eocene, ca. 35-40 MaBP) and Myanmar (Kachin amber, Cretaceous, ca. 100 MaBP). Larvae of the group are slender and elongated and live mostly in water. Yet, larvae are in fact very rare. So far, only slightly more than 30 larval specimens, counting all extant and fossil larvae, have been depicted in the literature. Here, we report numerous additional specimens, including extant larvae, but also fossil ones from Baltic and Kachin amber. Together with the already known ones, this sums up to over 100 specimens. We analysed quantitative aspects of the morphology of these larvae and compared them over time to identify changes in the diversity. Despite the enriched sample size, the data set is still unbalanced, with, for example, newly hatched larvae (several dozen specimens) only known from the Eocene. We expected little change in larval morphology over geological time, as indicated by earlier studies. However, on the contrary, we recognised morphologies present in fossils that are now extinct. This result is similar to those for other groups of lacewings which have a relic distribution today, as these have also suffered a loss in diversity in larval forms.

Quantitative analysis of lacewing larvae over more than 100 million years reveals a complex pattern of loss of morphological diversity

Loss of biodiversity and especially insect decline are widely recognised in modern ecosystems. This decline has an enormous impact due to the crucial ecological roles of insects as well as their economic relevance. For comparison, the fossil record can provide important insights on past biodiversity losses. One group of insects, for which a significant decline over the last 100 million years has often been postulated, but not demonstrated quantitatively, is Neuroptera (lacewings). Many adult lacewings are pollinators, while the larvae are mostly predators, which becomes very obvious from their prominent stylet-like mouthparts. We investigated the fossil record of larvae of all neuropteran lineages as well as a large share of extant neuropteran larvae. Based on these, we performed an outline analysis of the head with stylets. This analysis provides a quantitative frame for recognising the decline of lacewings since the Cretaceous, indicating also a severe loss of ecological roles.

Giant Jurassic dragon lacewing larvae with lacustrine palaeoecology represent the oldest fossil record of larval neuropterans

Neuropterans seem to be less specious among holometabolans, while they are in fact the relicts of a diverse group from the Mesozoic era. Their early radiation resulted in great family level morphological heterogeneity of extant neuropterans, especially of their larvae. The earliest previously reported fossil larvae of this group were from the Early Cretaceous, where they already showed high taxonomic diversity and an extremely wide range of variations in morphotypes. In this work, the earliest record of the larva of the neuropteran Palaeoneurorthus baii gen. et sp. nov. from the Middle Jurassic Daohugou Beds of China is described. The larvae, which have large and elongated bodies, straight stylets with curved apices, an extremely elongated cervix and an extended anterior lobe of pronotum, are placed in Nevrorthidae. The elongated cervix is probably a specialized adaptation for hunting small organisms. The palaeoenvironment of these larvae indicates that larvae of Nevrorthidae have exhibited stable aquatic ecology since the Middle Jurassic, and underwent a possible shift from lakes to more lotic yet constricted modern mountain rivulet habitats over time.

An Expanded View on the Morphological Diversity of Long-Nosed Antlion Larvae Further Supports a Decline of Silky Lacewings in the Past 100 Million Years

Lacewings have been suggested to be a relict group. This means that the group of lacewings, Neuroptera, should have been more diverse in the past, which also applies to many ingroups of Neuroptera. Psychopsidae, the group of silky lacewings, is one of the ingroups of Neuroptera which is relatively species-poor in the modern fauna. Larvae of the group Psychopsidae, long-nosed antlions, can be easily identified as such in being larvae of antlion-like lacewings without teeth in their stylets (=compound structure of mandible and maxilla), with empodia (=attachment structures on legs) and with a prominent forward-protruding labrum. Therefore, such larvae can also be recognised in the fossil record. An earlier study demonstrated a decline in the morphological diversity of long-nosed antlion larvae over the past 100 million years. Here, we report several dozen new long-nosed antlion larvae and expand the earlier quantitative study. Our results further corroborate the decline of silky lacewings. Yet, a lack of an indication of saturation indicates that we have still not approached the original diversity of long-nosed antlions in the Cretaceous.

Unraveling the evolutionary history of the snakefly family Inocelliidae (Insecta: Raphidioptera) through integrative phylogenetics

Inocelliidae is one of the two extant families of the holometabolan order Raphidioptera (snakeflies), with the modern fauna represented by seven genera and 44 species. The evolutionary history of the family is little-known. Here we present the first phylogenetic and biogeographical analyses based on a worldwide sampling of taxa and datasets combined with morphological characters and mitochondrial genomes, aiming to investigate the intergeneric phylogeny and historical biogeography of Inocelliidae. The phylogenetic inference from the combined analysis of morphological and molecular data recovered the sister-group relationship between a clade of (Negha + Indianoinocellia) + Sininocellia and a clade of Fibla + the Inocellia clade (interiorly nested by Amurinocellia and Parainocellia). Amurinocellia stat.r. and Parainocellia stat.r. et emend.n. are relegated to subgeneric status within Inocellia, whereas a newly erected subgenus of Inocellia, Epinocellia subgen.n., accommodates the former Parainocellia burmana (U. Aspöck and H. Aspöck, 1968) plus a new species Inocellia (Epinocellia) weii sp.n. Further, the Inocellia crassicornis group constitutes the nominotypical subgenus Inocellia stat.n., but the Inocellia fulvostigmata group is paraphyletic. Diversification within Inocelliidae is distinguished by an Eocene divergence leading to extant genera and a Miocene radiation of species. A biogeographical scenario depicts how the diverse inocelliid fauna from East Asia could have originated from western North America via dispersal across the Beringia during the early Tertiary, and how the Miocene ancestors of Inocellia could have accomplished long-distance dispersals via the Tibet-Himalayan corridor or eastern Palaearctic to western Palaearctic. Our results shed new light specifically on the evolution of Inocelliidae and, in general, the Raphidioptera.

Phylogenomic Analyses of the Tenthredinoidea Support the Familial Rank of Athaliidae (Insecta, Tenthredinoidea)

The systematic status of the genus Athalia and related genera is a perennial controversy in sawfly taxonomy. Several authors have hypothesized that the placement of Athalia within the Tenthredinidae is artificial, but no studies have focused on this topic. If the hypothesis that Athalia does not belong to Tenthredinidae can be supported, the taxonomic framework of Tenthredinoidea needs revision. We present a comprehensive phylogenomic study of Tenthredinoidae, focusing on the positions of Athalia and related genera by sampling 80 representatives mainly of the Tenthredinoidea, including Heptamelinae and Blasticotomidae. Our phylogenetic reconstructions based on nuclear genes and mitochondrial (mt) sequences support Athalia and related genera as a distinct clade sister to Tenthredinidae + (Cimbicidae + Diprionidae). A comparison of symphytan mitochondrial genomes reveals an innovative gene rearrangement pattern in Athaliidae, in which Dentathalia demonstrates a more ancestral pattern than Athalia and Hypsathalia. The lineage specificity of mt rRNA secondary structures also provides sufficient support to consider Athaliidae as a separate family. In summary, the phylogeny and genomic structural changes unanimously support the taxonomic treatment of Athaliidae as a family and the re-establishment of Dentathalia as a valid genus.

100 Million-year-old straight-jawed lacewing larvae with enormously inflated trunks represent the oldest cases of extreme physogastry in insects

Physogastry is a phenomenon occurring in Euarthropoda and describes an extreme inflation of (parts of) the trunk. It is best known from ticks, termite queens, or honey-pot ants, but can also be found in several other representatives of Euarthropoda. Physogastry has so far rarely been seen in the fossil record. We describe here an example of physogastry in two lacewing larvae (Neuroptera) enclosed in a single piece of Kachin amber (ca. 100 Ma old). We measured head and trunk ratios of different physogastric and non-physogastric representatives of Euarthropoda. Plotting these ratios shows that the new larvae, which display quite extremely inflated trunks, are very similar to ticks or honey-pot ants, but also to certain lacewing larvae of the group Berothidae (beaded lacewings). Outline analysis of head capsule and mouthparts (stylets) further suggests a position within Berothidae. Physogastry is presumed to be linked with living in confined spaces such as wood galleries or soil. Indeed, at least some larvae of Berothidae are known to live inside termite nests for part of their larval life phase, a habit the new larvae may also have had. The new record represents the oldest case of extreme physogastry in insects known to date.

Phylogenetic implications of the complete mitochondrial genome of Ogcogastersegmentator (Westwood, 1847) and first record of the genus Ogcogaster Westwood, 1847 from China (Neuroptera, Myrmeleontidae, Ascalaphinae)

Background

The genus Ogcogaster Westwood, 1847, which is endemic to the Oriental Region and contains only five species, has been recorded in India and Pakistan, but not in China. The genus was not sampled in any previous study on the phylogeny of Neuroptera and its affinity within Ascalaphinae is unclear.

New information

The owlfly species Ogcogastersegmentator (Westwood, 1847) is firstly recorded from China, based on a female specimen collected from Yunnan Province, which represents the first record of the genus Ogcogaster from China. The complete mitochondrial genome of this species is first sequenced and described. The phylogenetic analysis, based on all 13 PCGs and two rRNA genes of the owlfly mitogenomes determined so far, assigned O.segmentator into a monophyletic group with Libelloidesmacaronius (Scopoli, 1763) and Ascalohybrissubjacens (Walker, 1853).

A new species of beaded lacewings (Neuroptera, Berothidae) from mid-Cretaceous Myanmar amber

A new species of Berothidae, Jersiberotha musivum sp. nov., is described and illustrated from mid-Cretaceous (lowest Cenomanian) Myanmar amber. It is easily distinguished from other species of Berothidae by the configuration of the wing venation including: forewing with distinct areas of infuscation surrounding cross-veins and vein forks, all cross-veins simple prior to ScP-RA fusion, presence of two cross-veins ra-rp; absence of inner or outer graduate series of cross-veins; RP with three branches; and absence of ma-mp cross-veins and cua-cup cross-veins; while hind wing has cross-vein 1r-m absent. The previous diagnoses of Iceloberotha Grimaldi, 2000 and Jersiberotha Grimaldi, 2000 are quite unclear because some characters occur mosaically in both genera. In order to solve this problem and distinguish J. musivum from other species in the family, a new key to species of Berothidae from Myanmar amber has been provided and the diagnoses of Iceloberotha and Jersiberotha have been revised.

The Diversity of Aphidlion-like Larvae over the Last 130 Million Years

Simple Summary

The larvae of green lacewings and brown lacewings are called ‘aphidlions’, as they consume aphids. They play also an economic role as biological pest control. Aphidlions have, mostly, elongated spindle-shaped bodies, and similarly to most lacewing larvae, they possess a pair of venom-injecting compound jaws, also called stylets. Fossils that have been interpreted as aphidlions are known from amber of different ages (about 130, 100, 35, and 15 million years old). In this study, new aphidlion-like larvae are reported from about 100 million-year-old amber from Myanmar and about 35 million-year-old Baltic amber. The shapes of head and stylets were compared between the different time slices. With the newly described fossils and specimens from the literature, a total of 361 specimens could be included in the analysis: 78 fossil larvae, 188 extant larvae of brown lacewings, and 95 extant larvae of green lacewings. The results indicate that the diversity of head shapes stays about the same over time besides a certain increase in diversity of the head shapes in brown lacewing larvae. In certain other lacewings, a distinct decrease in the diversity of head shapes was observed in the larvae.

Abstract

Aphidlions are larvae of certain lacewings (Neuroptera), and more precisely larvae of the groups Chrysopidae, green lacewings, and Hemerobiidae, brown lacewings. The name ‘aphidlion’ originates from their ecological function as specialised predators of aphids. Accordingly, they also play an economic role as biological pest control. Aphidlions have, mostly, elongated spindle-shaped bodies, and similarly to most lacewing larvae they are equipped with a pair of venom-injecting stylets. Fossils interpreted as aphidlions are known to be preserved in amber from the Cretaceous (130 and 100 million years ago), the Eocene (about 35 million years ago) and the Miocene (about 15 million years ago) ages. In this study, new aphidlion-like larvae are reported from Cretaceous amber from Myanmar (about 100 million years old) and Eocene Baltic amber. The shapes of head and stylets were compared between the different time slices. With the newly described fossils and specimens from the literature, a total of 361 specimens could be included in the analysis: 70 specimens from the Cretaceous, 5 from the Eocene, 3 from the Miocene, 188 extant larvae of Chrysopidae, and 95 extant larvae of Hemerobiidae. The results indicate that the diversity of head shapes remains largely unchanged over time, yet there is a certain increase in the diversity of head shapes in the larvae of Hemerobiidae. In certain other groups of Neuroptera, a distinct decrease in the diversity of head shapes in larval stages was observed.

The first cave associated genus of Berothidae (Insecta: Neuroptera), and a new interpretation of the subfamily Cyrenoberothinae

A new genus of Berothidae (Neuroptera), Speleoberotha gen. nov., with two new species from Brazil, Speleoberotha mineira sp. nov. and Speleoberotha palomae sp. nov., are herein presented. These are the first cave-associated species of Berothidae ever recorded. The new genus shares some characters with the two extant genera of the subfamily Cyrenoberothinae, Cyrenoberotha and Manselliberotha, and other characters are shared with three fossil genera, Microberotha, Protoberotha and Sibelliberotha. This intermediate nature of the new genus was reinforced by the phylogenetic analyses presented here, which recovered Speleoberotha gen. nov. as sister to Sibelliberotha but closely associated with the extant Cyrenoberothinae. In this sense, a new concept of the subfamily Cyrenoberothinae is presented here, now including Speleoberotha gen. nov. and the three fossil genera together with Cyrenoberotha and Manselliberotha. We discuss the biogeographical history of the new concept of Cyrenoberothinae, suggesting that the clade originated in Gondwana. We also provide an identification key for the genera of Cyrenoberothinae.

Transcriptomics provides a robust framework for the relationships of the major clades of cladobranch sea slugs (Mollusca, Gastropoda, Heterobranchia), but fails to resolve the position of the enigmatic genus Embletonia

Background

The soft-bodied cladobranch sea slugs represent roughly half of the biodiversity of marine nudibranch molluscs on the planet. Despite their global distribution from shallow waters to the deep sea, from tropical into polar seas, and their important role in marine ecosystems and for humans (as targets for drug discovery), the evolutionary history of cladobranch sea slugs is not yet fully understood.

Results

To enlarge the current knowledge on the phylogenetic relationships, we generated new transcriptome data for 19 species of cladobranch sea slugs and two additional outgroup taxa (Berthella plumula and Polycera quadrilineata). We complemented our taxon sampling with previously published transcriptome data, resulting in a final data set covering 56 species from all but one accepted cladobranch superfamilies. We assembled all transcriptomes using six different assemblers, selecting those assemblies that provided the largest amount of potentially phylogenetically informative sites. Quality-driven compilation of data sets resulted in four different supermatrices: two with full coverage of genes per species (446 and 335 single-copy protein-coding genes, respectively) and two with a less stringent coverage (667 genes with 98.9% partition coverage and 1767 genes with 86% partition coverage, respectively). We used these supermatrices to infer statistically robust maximum-likelihood trees. All analyses, irrespective of the data set, indicate maximal statistical support for all major splits and phylogenetic relationships at the family level. Besides the questionable position of Noumeaella rubrofasciata, rendering the Facelinidae as polyphyletic, the only notable discordance between the inferred trees is the position of Embletonia pulchra. Extensive testing using Four-cluster Likelihood Mapping, Approximately Unbiased tests, and Quartet Scores revealed that its position is not due to any informative phylogenetic signal, but caused by confounding signal.

Conclusions

Our data matrices and the inferred trees can serve as a solid foundation for future work on the taxonomy and evolutionary history of Cladobranchia. The placement of E. pulchra, however, proves challenging, even with large data sets and various optimization strategies. Moreover, quartet mapping results show that confounding signal present in the data is sufficient to explain the inferred position of E. pulchra, again leaving its phylogenetic position as an enigma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01944-0.

Similar pattern, different paths: tracing the biogeographical history of Megaloptera (Insecta: Neuropterida) using mitochondrial phylogenomics

The sequential breakup of the supercontinent Pangaea since the Middle Jurassic is one of the crucial factors that has driven the biogeographical patterns of terrestrial biotas. Despite decades of effort searching for concordant patterns between diversification and continental fragmentation among taxonomic groups, increasing evidence has revealed more complex and idiosyncratic scenarios resulting from a mixture of vicariance, dispersal and extinction. Aquatic insects with discreet ecological requirements, low vagility and disjunct distributions represent a valuable model for testing biogeographical hypotheses by reconstructing their distribution patterns and temporal divergences. Insects of the order Megaloptera have exclusively aquatic larvae, their adults have low vagility, and the group has a highly disjunct geographical distribution. Here we present a comprehensive phylogeny of Megaloptera based on a large-scale mitochondrial genome sequencing of 99 species representing >90% of the world genera from all major biogeographical regions. Molecular dating suggests that the deep divergence within Megaloptera pre-dates the breakup of Pangaea. Subsequently, the intergeneric divergences within Corydalinae (dobsonflies), Chauliodinae (fishflies) and Sialidae (alderflies) might have been driven by both vicariance and dispersal correlated with the shifting continent during the Cretaceous, but with strikingly different and incongruent biogeographical signals. The austral distribution of many corydalids appears to be a result of colonization from Eurasia through southward dispersal across Europe and Africa during the Cretaceous, whereas a nearly contemporaneous dispersal via northward rafting of Gondwanan landmasses may account for the colonization of extant Eurasian alderflies from the south.

DNA Barcoding of Portuguese Lacewings (Neuroptera) and Snakeflies (Raphidioptera) (Insecta, Neuropterida)

The orders Neuroptera and Raphidioptera include the species of insects known as lacewings and snakeflies, respectively. In Portugal, these groups account for over 100 species, some of which are very difficult to identify by morphological analysis. This work is the first to sample and DNA sequence lacewings and snakeflies of Portugal. A reference collection was built with captured specimens that were identified morphologically. DNA barcode sequences of 658 bp were obtained from 243 specimens of 54 species. The results showed that most species can be successfully identified through DNA barcoding, with the exception of seven species of Chrysopidae (Neuroptera). Additionally, the first published distribution data are presented for Portugal for the neuropterans Gymnocnemiavariegata (Schneider, 1845) and Myrmecaelurus (Myrmecaelurus) trigrammus (Pallas, 1771).

The first mitochondrial genome of spongillafly from Asia (Neuroptera: Sisyridae: Sisyra aurorae Navás, 1933) and phylogenetic implications of Osmyloidea

The spongillafly species Sisyra aurorae Navás, 1933 (Neuroptera: Sisyridae) is an endemic species in China and is first recorded from Shanghai. The mitogenome of this species is sequenced, representing the first mitogenome of Sisyridae from Asia. The nearly complete mitogenome is 15,634 bp, which contains 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a control region. The gene order and arrangement are similar to other lacewing mitogenomes. Both Bayesian and maximum likelihood analyses based on 13 PCGs recovered the interfamilial phylogeny within Osmyloidea as Sisyridae + (Nevrorthidae + Osmylidae).

Discovery of wing imaginal discs in the penultimate instar of the lacewing Mallada desjardinsi (Insecta: Neuroptera: Chrysopidae) with histological notes on postembryonic imaginal disc development

Holometabolous insects are alternatively named "Endopterygota" because, in the larvae of many taxa, the wing primordia in the lateral regions of the meso- and metathoracic segments form more or less invaginated structures called wing imaginal discs. Holometabolous insects exhibit differential developmental timing of the wing during ontogeny. The condition in which wing growth is deferred until the end of larval life has been considered ancestral, whereas early disc formation has been recognized as the derived condition. Even though wing disc development in holometabolous insects has been studied extensively in select groups, many questions remain about the development of the wing imaginal disc in the orders Raphidioptera, Megaloptera, Neuroptera, and Mecoptera. To clarify whether the wing imaginal disc of Neuroptera is typical of the derived condition, we examined the ontogeny of the wing imaginal discs in the lacewing Mallada desjardinsi histologically. Using both light microscopy and transmission electron microscopy, we were able to recognize wing imaginal discs in the penultimate larval instar (prefinal larval instar) of this species. To date, neuropteran insects have been characterized as having late-forming wing imaginal discs. However, our findings show that the developmental pattern of the wing imaginal discs within the Neuroptera represents a more derived pattern of development in the Holometabola than was assumed previously.