Phylogeny and Evolution of Lepidoptera

Light intensity differentially mediates the life cycle of lepidopteran leaf feeders and stem borers

BACKGROUND

Leaf feeders, such as Spodoptera frugiperda and Spodoptera litura, and stem borers Ostrinia furnacalis and Chilo suppressalis, occupy two different niches and are well adapted to their particular environments. Borer larvae burrow and inhabit the interior of stems, which are relatively dark. By contrast, the larvae of leaf feeders are exposed to sunlight during feeding. We therefore designed series of experiments to evaluate the effect of light intensity (0, 2000, and 10 000 lx) on these pests with different feeding modes.

RESULTS

The development of all four pests was significantly delayed at 0 lx. Importantly, light intensity affected the development of both male and female larvae of borers, but only significantly affected male larvae of leaf feeders. Furthermore, the proportion of female offspring of leaf feeders increased with increasing light intensity (S. frugiperda: 33.89%, 42.26%, 57.41%; S. litura: 38.90%, 51.75%, 65.08%), but no significant differences were found in stem borers. This research also revealed that the survival rate of female leaf feeders did not vary across light intensities, but that of males decreased with increasing light intensity (S. frugiperda: 97.78%, 85.86%, 61.21%; S. litura: 95.83%, 73.54%, 58.99%).

CONCLUSION

These results improve our understanding of how light intensity affects sex differences in important lepidopteran pests occupying different feeding niches and their ecological interactions with abiotic factors in agroecosystems. © 2024 Society of Chemical Industry.

How Do Butterflies Use Silk to Attach their Pupae to Trees?

Butterflies constitute approximately 10% of lepidopteran insects, and along with silkworms, they can produce silk; however, this feature is often ignored. In the present study, we observed two primary methods used by butterflies to hang pupae on trees using silk: pupa adheraena (Danaus chrysippus) and pupa contigua (Papilio polytes). Anchoring the abdominal ends of pupae with a silk pad was the most common method used in both cases, whereas wrapping silk around the body using a silk girdle was a method unique to pupa contigua. The connection between the cremaster and silk pad was observed to be similar to that between the hook and loop of a Velcro fastener, except that the cremaster hook is anchor-shaped rather than being a single hook. Such a connection will remain secure, ensuring the safety of the pupae during exposure to wind and rain. Through determining the mechanical properties of silk, the performance of butterfly silk was found to be weaker than that of silkworm silk. Therefore, the P. polytes silk girdle adopts the strategy of merging a dozen silk threads to improve its strength and toughness, thereby making it difficult to break. In addition, we explained how the protein sequence and structure of butterfly silk impact its performance. In conclusion, we discovered that butterfly pupae develop unique body features to establish secure bonds with silk. This enables them to effectively undergo metamorphosis and endure harsh weather conditions and surroundings.

Phylogenomic data exploration with increased sampling provides new insights into the higher-level relationships of butterflies and moths (Lepidoptera)

A robust and stable phylogenetic framework is a fundamental goal of evolutionary biology. As the third largest insect order in the world following Coleoptera and Diptera, Lepidoptera (butterflies and moths) play a central role in almost every terrestrial ecosystem as indicators of environmental change and serve as important models for biologists exploring questions related to ecology and evolutionary biology. However, for such a charismatic insect group, the higher-level phylogenetic relationships among its superfamilies are still poorly resolved. Compared to earlier phylogenomic studies, we increased taxon sampling among Lepidoptera (37 superfamilies and 68 families containing 263 taxa) and acquired a series of large amino-acid datasets from 69,680 to 400,330 for phylogenomic reconstructions. Using these datasets, we explored the effect of different taxon sampling with significant increases in the number of included genes on tree topology by considering a series of systematic errors using maximum-likelihood (ML) and Bayesian inference (BI) methods. Moreover, we also tested the effectiveness in topology robustness among the three ML-based models. The results showed that taxon sampling is an important determinant in tree robustness of accurate lepidopteran phylogenetic estimation. Long-branch attraction (LBA) caused by site-wise heterogeneity is a significant source of bias giving rise to unstable positions of ditrysian groups in phylogenomic reconstruction. Phylogenetic inference showed the most comprehensive framework to reveal the relationships among lepidopteran superfamilies, and presented some newly relationships with strong supports (Papilionoidea was sister to Gelechioidea and Immoidea was sister to Galacticoidea, respectively), but limited by taxon sampling, the relationships within the species-rich and relatively rapid radiation Ditrysia and especially Apoditrysia remain poorly resolved, which need to increase taxon sampling for further phylogenomic reconstruction. The present study demonstrates that taxon sampling is an important determinant for an accurate lepidopteran tree of life and provides some essential insights for future lepidopteran phylogenomic studies.

A Female-Biased Chemosensory Protein PxutCSP19 in the Antennae of Papilio xuthus Tuned to Host Volatiles and Insecticides

Chemosensory protein (CSP) genes significantly enriched in the female antennae are potential molecular candidates for mediating female oviposition behaviors. In this study, we presented the interaction mechanisms of a female-antenna-biased PxutCSP19 in Papilio xuthus to 47 host volatiles, four biopesticides and 24 synthetic insecticides. Using a bioinformatics-based homology search, 22 genes orthologous to PxutCSP19 were identified from 22 other Papilio butterflies with high sequence identities to each other (73.20~98.72%). Multiple alignment analyses revealed a particularly extended N-terminus of Papilio CSP19s (an average of 154 residues) compared to insects' typical CSPs (approximately 120 residues). The expression profiles indicated that PxutCSP19 was significantly enriched in the female antennae, with a 31.81-fold difference relative to the male antennae. In ligand-binding assays, PxutCSP19 could strongly bind six host odorants with high affinities, ranging from dissociation constant (Ki) values of 20.44 ± 0.64 μM to 22.71 ± 0.73 μM. Notably, this protein was tuned to a monoterpenoid alcohol, linalool, which generally existed in the Rutaceae plants and elicited electrophysiological and behavioral activities of the swallowtail butterfly. On the other hand, PxutCSP19 was also capable of binding eight insecticides with stronger binding abilities (Ki < 12 μM) compared to host odorants. When an extended N-terminal region of PxutCSP19 was truncated into two different proteins, they did not significantly affect the binding of PxutCSP19 to ligands with high affinities, suggesting that this extended N-terminal sequences were not involved in the specificity of ligand recognition. Altogether, our study sheds light on the putative roles of PxutCSP19 enriched in the female antennae of P. xuthus in the perception of host volatiles and the sequestering of insecticides, and it complements the knowledge of butterfly CSPs in olfaction and insecticide resistance.

Vertical stratification and defensive traits of caterpillars against parasitoids in a lowland tropical forest in Cameroon

Insect herbivores and their parasitoids play a crucial role in terrestrial trophic interactions in tropical forests. These interactions occur across the entire vertical gradient of the forest. This study compares how caterpillar communities, and their parasitism rates, vary across vertical strata and between caterpillar defensive strategies in a semi deciduous tropical forest in Nditam, Cameroon. Within a 0.1 ha plot, all trees with a diameter at breast height (DBH) ≥ 5 cm were felled and systematically searched for caterpillars. We divided the entire vertical gradient of the forest into eight, five-metre strata. All caterpillars were assigned to a stratum based on their collection height, reared, identified, and classified into one of three defensive traits: aposematic, cryptic and shelter-building. Caterpillar species richness and diversity showed a midstory peak, whereas density followed the opposite pattern, decreasing in the midstory and then increasing towards the highest strata. This trend was driven by some highly dense shelter-building caterpillars in the upper canopy. Specialisation indices indicated decreasing levels of caterpillar generality with increasing height, a midstory peak in vulnerability, and increasing connectance towards the upper canopy, although the latter was likely driven by decreasing network size. Both aposematic and shelter-building caterpillars had significantly higher parasitism rates than cryptic caterpillars. Our results highlight nuanced changes in caterpillar communities across forest strata and provide evidence that defences strategies are important indicators of parasitism rates in caterpillars and that both aposematic and shelter-building caterpillars could be considered a "safe haven" for parasitoids.

Virus-host coevolutionary analyses of an Alphabaculovirus with a wide host range

Baculoviruses are highly host specific, and their host range is usually restricted to a single or a few closely related insect species, except for few virus species, e.g. Alphabaculovirus aucalifonicae and Alphabaculovirus mabrassicae. In this study, two new alphabaculovirus isolates were isolated from the larvae of Mamestra brassicae and Mythimna separata, which were named as Mamestra brassicae multiple nucleopolyhedrovirus isolate QD (MbMNPV-QD) and Mythimna separata multiple nucleopolyhedrovirus isolate Hb (MyseMNPV-Hb), respectively. The Kimura two-parameter values based on the concatenated 38 core genes of baculovirus revealed that MbMNPV (isolates QD/CHb1/K1/CTa), MyseMNPV-Hb, Helicoverpa armigera multiple nucleopolyhedrovirus (HearMNPV) and Mamestra configurata nucleopolyhedrovirus B (MacoNPV-B) were different isolates of a same virus species. A phylogenetic tree of baculoviruses and nudiviruses constructed from their 20 homologous gene sequences, and that of their isolated hosts constructed from 13 protein-coding genes of the insect mitochondrial genomes, were used to analyse the coevolution of baculoviruses with their isolated hosts. The results showed that M. brassicae was the most likely ancestral host of these virus isolates, included MbMNPV isolates, MyseMNPV-Hb, HearMNPV, and MacoNPV-B. Therefore, we concluded that these virus isolates belong to the existing virus species - Alphabaculovirus mabrassicae with M. brassicae as their ancestral host.

Toward an Integrated Understanding of the Lepidoptera Microbiome

Research over the past 30 years has led to a widespread acceptance that insects establish widespread and diverse associations with microorganisms. More recently, microbiome research has been accelerating in lepidopteran systems, leading to a greater understanding of both endosymbiont and gut microorganisms and how they contribute to integral aspects of the host. Lepidoptera are associated with a robust assemblage of microorganisms, some of which may be stable and routinely detected in larval and adult hosts, while others are ephemeral and transient. Certain microorganisms that populate Lepidoptera can contribute significantly to the hosts' performance and fitness, while others are inconsequential. We emphasize the context-dependent nature of the interactions between players. While our review discusses the contemporary literature, there are major avenues yet to be explored to determine both the fundamental aspects of host-microbe interactions and potential applications for the lepidopteran microbiome; we describe these avenues after our synthesis.

Novel insight into lepidopteran phylogenetics from the mitochondrial genome of the apple fruit moth of the family Argyresthiidae

BACKGROUND

The order Lepidoptera has an abundance of species, including both agriculturally beneficial and detrimental insects. Molecular data has been used to investigate the phylogenetic relationships of major subdivisions in Lepidoptera, which has enhanced our understanding of the evolutionary relationships at the family and superfamily levels. However, the phylogenetic placement of many superfamilies and/or families in this order is still unknown. In this study, we determine the systematic status of the family Argyresthiidae within Lepidoptera and explore its phylogenetic affinities and implications for the evolution of the order. We describe the first mitochondrial (mt) genome from a member of Argyresthiidae, the apple fruit moth Argyresthia conjugella. The insect is an important pest on apples in Fennoscandia, as it switches hosts when the main host fails to produce crops.

RESULTS

The mt genome of A. conjugella contains 16,044 bp and encodes all 37 genes commonly found in insect mt genomes, including 13 protein-coding genes (PCGs), two ribosomal RNAs, 22 transfer RNAs, and a large control region (1101 bp). The nucleotide composition was extremely AT-rich (82%). All detected PCGs (13) began with an ATN codon and terminated with a TAA stop codon, except the start codon in cox1 is ATT. All 22 tRNAs had cloverleaf secondary structures, except trnS1, where one of the dihydrouridine (DHU) arms is missing, reflecting potential differences in gene expression. When compared to the mt genomes of 507 other Lepidoptera representing 18 superfamilies and 42 families, phylogenomic analyses found that A. conjugella had the closest relationship with the Plutellidae family (Yponomeutoidea-super family). We also detected a sister relationship between Yponomeutoidea and the superfamily Tineidae.

CONCLUSIONS

Our results underline the potential importance of mt genomes in comparative genomic analyses of Lepidoptera species and provide valuable evolutionary insight across the tree of Lepidoptera species.

Phylogeography of Two Enigmatic Sulphur Butterflies, Colias mongola Alphéraky, 1897 and Colias tamerlana Staudinger, 1897 (Lepidoptera, Pieridae), with Relations to Wolbachia Infection

The genus Colias Fabricius, 1807 includes numerous taxa and forms with uncertain status and taxonomic position. Among such taxa are Colias mongola Alphéraky, 1897 and Colias tamerlana Staudinger, 1897, interpreted in the literature either as conspecific forms, as subspecies of different but morphologically somewhat similar Colias species or as distinct species-level taxa. Based on mitochondrial and nuclear DNA markers, we reconstructed a phylogeographic pattern of the taxa in question. We recover and include in our analysis DNA barcodes of the century-old type specimens, the lectotype of C. tamerlana deposited in the Natural History Museum (Museum für Naturkunde), Berlin, Germany (ZMHU) and the paralectotype of C. tamerlana and the lectotype of C. mongola deposited in the Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia (ZISP). Our analysis grouped all specimens within four (HP_I-HP_IV) deeply divergent but geographically poorly structured clades which did not support nonconspecifity of C. mongola-C. tamerlana. We also show that all studied females of the widely distributed haplogroup HP_II were infected with a single Wolbachia strain belonging to the supergroup B, while the males of this haplogroup, as well as all other investigated specimens of both sexes, were not infected. Our data highlight the relevance of large-scale sampling dataset analysis and the need for testing for Wolbachia infection to avoid erroneous phylogenetic reconstructions and species misidentification.

SPSL1 is essential for spermatophore formation and sperm activation in Spodoptera frugiperda

The reproductive process in various species has undergone evolutionary adaptations at both the physiological and molecular levels, playing a significant role in maintaining their populations. In lepidopteran insects, the spermatophore is a unique structure formed in the female reproductive system, in which sperm storage and activation take place. It is known that the formation of the spermatophore is regulated by seminal fluid proteins derived from males. However, studies investigating the genetic mechanisms behind spermatophore formation in lepidopterans have been limited. In this study, our focus was on SPSL1, a gene that encodes a trypsin-type seminal fluid protein in Spodoptera frugiperda, a pest species with global invasive tendencies. Our findings revealed that SPSL1 expression was predominantly observed in the male reproductive tracts, and the disruption of this gene resulted in male sterility. Surprisingly, fluorescence analysis indicated that the absence of SPSL1 did not affect spermatogenesis or sperm migration within the male reproductive system. However, when females mated with SPSL1-mutant males, several defects were observed. These included disruptions in spermatophore formation, sperm activation in the copulatory bursae, and sperm migration into the spermathecae. Additionally, mass spectrometry analysis highlighted reduced levels of energy-related metabolites, suggesting that SPSL1 plays an essential role in promoting hydrolysis reactions during copulation. Consequently, our study demonstrates that SPSL1 is crucial for male fertility due to its functions in spermatophore formation and sperm activation. This research provides valuable insights into the genetic factors underlying reproductive processes in lepidopteran insects and sheds light on potential strategies for controlling invasive pest populations.

Functional characterization of four antenna-biased chemosensory proteins in Dioryctria abietella reveals a broadly tuned olfactory DabiCSP1 and its key residues in ligand-binding

The orientation of the oligophagous cone-feeding moth Dioryctria abietella (Lepidoptera: Pyralidae) to host plants primarily relies on olfactory-related proteins, particularly those candidates highly expressed in antennae. Here, through a combination of expression profile, ligand-binding assay, molecular docking and site-directed mutagenesis strategies, we characterized the chemosensory protein (CSP) gene family in D. abietella. Quantitative real-time PCR (qPCR) analyses revealed the detectable expression of all 22 DabiCSPs in the antennae, of which seven genes were significantly enriched in this tissue. In addition, the majority of the genes (19/22 relatives) had the expression in at least one reproductive tissue. In the interactions of four antenna-dominant DabiCSPs and different chemical classes, DabiCSP1 was broadly tuned to 27 plant-derived odors, three man-made insecticides and one herbicide with high affinities (Ki < 6.60 μM). By contrast, three other DabiCSPs (DabiCSP4, CSP6 and CSP17) exhibited a narrow odor binding spectrum, in response to six compounds for each protein. Our mutation analyses combined with molecular docking simulations and binding assays further identified four key residues (Tyr25, Thr26, Ile65 and Val69) in the interactions of DabiCSP1 and ligands, of which binding abilities of this protein to 12, 15, 16 and three compounds were significantly decreased compared to the wildtype protein, respectively. Our study reveals different odor binding spectra of four DabiCSPs enriched in antennae and identifies key residues responsible for the binding of DabiCSP1 and potentially active compounds for the control of this pest.

Complete mitochondrial genome of Parasa sinica: New insights into the phylogeny of Limacodidae

In this study, the whole mitochondrial genome (mitogenome) of Parasa sinica was sequenced. It contains 15,306 base pairs (bp), 13 protein-coding genes (PCGs), two ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), and one non-coding regulatory area (CR), all of which are shared by other lepidopterans. It follows the same gene order as ordinary lepidopterans. Further, out of these 37 genes, 23 are present on the heavy strand whereas the remaining 14 are located on the light strand. The A + T composition of the mitogenome is relatively high. Although P. sinica has a negative AT-skew and GC-skew, the GC-skew value is significantly lower than the AT-skew value. All PCGs, with the exception of CO1, carry the same start codon (ATN). All tRNAs exhibit the usual cloverleaf secondary structure. We identified the conserved motif "ATAGA + poly-T″ found in other lepidopteran insects at the beginning of the CR. We collected the concatenated PCGs sequences in the mitochondrial genome of 15 species of Zygaenoidea, with the sequences of Geometridae as outgroups, including P. sinica, and constructed phylogenetic trees using Bayesian inference (BI) and maximum likelihood (ML) methods. The monolineage of each superfamily is usually well supported. Based on phylogenetic analysis, P. sinica is a member of family Limacodidae, strongly supporting the monophyly of the Zygaenoidea groups.

Pheromones emitted by both female and male moths regulate coordination between the sexes for Agriphila aeneociliella (Lepidoptera: Crambidae)

The complex and efficient sex pheromone communication system in insects is essential for reproduction and for reproductive isolation of species. In moths, sex pheromone communication starts with male attraction to compounds emitted by females; only a few species act in the reverse. However, how the pheromones that are emitted by both sexes co-regulate and coordinate mate finding and mating remains unknown. Here, we identified both the male and female pheromones of Eastern Grass Veneer moth, Agriphila aeneociliella (Lepidoptera: Crambidae), and demonstrated their efficiency in manipulating behavioral responses of the opposite sex. Combining data from analysis of gas chromatography-electroantennogram detection, gas chromatography-mass spectrometry, and olfactory behavior assays, the female pheromone of A. aeneociliella was identified as (Z,Z,Z)-9,12,15-octadecatrienal and (Z)-9-hexadecenyl acetate, while the male pheromone was determined to be 1-nonanal. Both the 2 individual components of the female pheromone and their binary mixture were significantly attractive to males, and the 1-nonanal male pheromone induced strong electrophysiological responses in females and induced attraction of females in a Y-tube olfactory test. Depending on the concentration of 1-nonanal, its addition to the binary mixture of the female pheromone either enhanced (10-3 or 10-2  μg/μL) or reduced (1 μg/μL) the aphrodisiac effect of the mixture on males. In wind-tunnel bioassays, different concentrations of pheromones, including the binary mixture of female pheromone and the mixture of male and female pheromones, had significant effects on male behavior. Our findings suggested that the blend of both female and male pheromones plays a significant role in the sexual communication system in some moths.

The fauna of the family Adelidae (Insecta, Lepidoptera, Adeloidea) from China

Ninety-eight species of the family Adelidae, belonging to three genera in two subfamilies, were recorded and described in China, with illustrations of the adults and their genitalia. Keys to subfamilies, genera and species are also provided. Twenty-four new species are described, nine species are newly recorded from China, and four new combinations are made. Ecological photos and DNA barcodes of some species are provided, and the phylogenetic analysis based on cytochrome c oxidase subunit I (COI) sequences are conducted. The new taxa are as follows: Nemophora pseudalbiantennella Liao, Hirowatari & Huang, sp. nov., N. badagongshana Liao, Hirowatari & Huang, sp. nov., N. longlabiae Liao, Hirowatari & Huang, sp. nov., N. quadrata Liao, Hirowatari & Huang, sp. nov., N. basalistriata Liao, Hirowatari & Huang, sp. nov., N. digitata Liao, Hirowatari & Huang, sp. nov., N. duplicifascia Liao, Hirowatari & Huang, sp. nov., N. hunanensis Liao, Hirowatari & Huang, sp. nov., N. purpurata Liao, Hirowatari & Huang, sp. nov., N. arcuatifasciata Liao, Hirowatari & Huang, sp. nov., N. caeruliantenna Liao, Hirowatari & Huang, sp. nov., N. xizangensis Liao, Hirowatari & Huang, sp. nov., N. caerulea Liao, Hirowatari & Huang, sp. nov., N. songgangensis Liao, Hirowatari & Huang, sp. nov., N. conjugata Liao, Hirowatari & Huang, sp. nov., N. latilobula Liao, Hirowatari & Huang, sp. nov., N. longispina Liao, Hirowatari & Huang, sp. nov., N. ganziensis Liao, Hirowatari & Huang, sp. nov., N. jiajinshana Liao, Hirowatari & Huang, sp. nov., N. litangensis Liao, Hirowatari & Huang, sp. nov., N. tianpingshana Liao, Hirowatari & Huang, sp. nov., N. triangulifascia Liao, Hirowatari & Huang, sp. nov., N. yajiagengensis Liao, Hirowatari & Huang, sp. nov., and N. bispina Liao, Hirowatari & Huang, sp. nov. The newly recorded taxa from China are: Nematopogon distinctus Yasuda, 1957, Adela nobilis Christoph, 1882, A. praepilosa Hirowatari, 1997, Nemophora albiantennella Issiki, 1930, N. chionites (Meyrick, 1907), N. smaragdaspis (Meyrick, 1924), N. trimetrella Stringer, 1930, N. optima (Butler, 1878), and N. bifasciatella Issikii, 1930. The new combinations are N. servata (Meyrick, 1925) com. nov., N. diplophragma (Meyrick, 1938) com. nov., N. chionella (Caradja, 1935) com. nov., and N. chrysocharis (Caradja, 1938) com. nov.

Determining the complete mitochondrial genome of Tethea albicostata (Lepidoptera: Drepanidae) and phylogenetic analysis

Tethea albicostata is a widely distributed insect species in northern and central China. To date, few studies have been conducted on this species, with the exception of morphological taxonomy studies. Here, we report the complete mitochondrial genome of T. albicostata collected in China. The circular-mapping mitogenome is 15,308 bp in length, with an overall A + T content of 80.52%, encoding 2 ribosomal RNA genes, 22 transfer RNA genes, and 13 protein-coding genes. The gene arrangement and components of T. albicostata are identical to those of most other Lepidopteran insects. Phylogenetic analysis based on mitogenomes showed that T. albicostata is grouped with Drepana pallida, which belongs to the same family as Drepanidae. The family Drepanidae formed a separate branch from other families in the phylogenetic tree. This study determined the second mitochondrial genome of the Drepanidae species.

Dichotomous sperm in Lepidopteran insects: a biorational target for pest management

Lepidoptera are unusual in possessing two distinct kinds of sperm, regular nucleated (eupyrene) sperm and anucleate (apyrene) sperm ('parasperm'). Sperm of both types are transferred to the female and are required for male fertility. Apyrene sperm play 'helper' roles, assisting eupyrene sperm to gain access to unfertilized eggs and influencing the reproductive behavior of mated female moths. Sperm development and behavior are promising targets for environmentally safer, target-specific biorational control strategies in lepidopteran pest insects. Sperm dimorphism provides a wide window in which to manipulate sperm functionality and dynamics, thereby impairing the reproductive fitness of pest species. Opportunities to interfere with spermatozoa are available not only while sperm are still in the male (before copulation), but also in the female (after copulation, when sperm are still in the male-provided spermatophore, or during storage in the female's spermatheca). Biomolecular technologies like RNAi, miRNAs and CRISPR-Cas9 are promising strategies to achieve lepidopteran pest control by targeting genes directly or indirectly involved in dichotomous sperm production, function, or persistence.

Identification and Expression of Integrins during Testicular Fusion in Spodoptera litura

Integrin members are cell adhesion receptors that bind to extracellular matrix (ECM) proteins to regulate cell-cell adhesion and cell-ECM adhesion. This process is essential for tissue development and organogenesis. The fusion of two testes is a physiological phenomenon that is required for sperm production and effective reproduction in many Lepidoptera. However, the molecular mechanism of testicular fusion is unclear. In Spodoptera litura, two separated testes fuse into a single testis during the larva-to-pupa transformation. We identified five α and five β integrin subunits that were closely associated with testicular fusion. Integrin α1 and α2 belong to the position-specific 1 (PS1) and PS2 groups, respectively. Integrin α3, αPS1/αPS2, and αPS3 were clustered into the PS3 group. Integrin β1 belonged to the insect β group, and β2, β3, and β5 were clustered in the βν group. Among these integrins, α1, α2, α3, αPS1/PS2, αPS3, β1, and β4 subunits were highly expressed when the testes fused. However, their expression levels were much lower before and after the fusion of the testis. The qRT-PCR and immunohistochemistry analyses indicated that integrin β1 mRNA and the protein were highly expressed in the peritoneal sheath of the testis, particularly when the testes fused. These results indicate that integrins might participate in S. litura testicular fusion.

Immune functions of pattern recognition receptors in Lepidoptera

Pattern recognition receptors (PRRs), as the "sensors" in the immune response, play a prominent role in recognizing pathogen-associated molecular patterns (PAMPs) and initiating an effective defense response to pathogens in Lepidoptera. It is becoming increasingly clear that damage-associated molecular patterns (DAMPs) normally play a physiological role within cells; however, when exposed to extracellular, they may become "part-time" critical signals of the immune response. Based on research in recent years, we review herein typical PRRs of Lepidoptera, including peptidoglycan recognition protein (PGRP), gram-negative binding protein (GNBP), β-1,3-glucan recognition protein (βGRP), C-type lectin (CTL), and scavenger receptor (SR). We also outline the ways in which DAMPs participate in the immune response and the correlation between PRRs and immune escape. Taken together, these findings suggest that the role of PRRs in insect innate immunity may be much greater than expected and that it is possible to recognize a broader range of signaling molecules.

Chromosomal conservatism vs chromosomal megaevolution: enigma of karyotypic evolution in Lepidoptera

In the evolution of many organisms, periods of slow genome reorganization (= chromosomal conservatism) are interrupted by bursts of numerous chromosomal changes (= chromosomal megaevolution). Using comparative analysis of chromosome-level genome assemblies, we investigated these processes in blue butterflies (Lycaenidae). We demonstrate that the phase of chromosome number conservatism is characterized by the stability of most autosomes and dynamic evolution of the sex chromosome Z, resulting in multiple variants of NeoZ chromosomes due to autosome-sex chromosome fusions. In contrast during the phase of rapid chromosomal evolution, the explosive increase in chromosome number occurs mainly through simple chromosomal fissions. We show that chromosomal megaevolution is a highly non-random canalized process, and in two phylogenetically independent Lysandra lineages, the drastic parallel increase in number of fragmented chromosomes was achieved, at least partially, through reuse of the same ancestral chromosomal breakpoints. In species showing chromosome number doubling, we found no blocks of duplicated sequences or duplicated chromosomes, thus refuting the hypothesis of polyploidy. In the studied taxa, long blocks of interstitial telomere sequences (ITSs) consist of (TTAGG)_n arrays interspersed with telomere-specific retrotransposons. ITSs are sporadically present in rapidly evolving Lysandra karyotypes, but not in the species with ancestral chromosome number. Therefore, we hypothesize that the transposition of telomeric sequences may be triggers of the rapid chromosome number increase. Finally, we discuss the hypothetical genomic and population mechanisms of chromosomal megaevolution and argue that the disproportionally high evolutionary role of the Z sex chromosome can be additionally reinforced by sex chromosome-autosome fusions and Z-chromosome inversions.

Chromosome-Level Genome Assembly of Papilio elwesi Leech, 1889 (Lepidoptera: Papilionidae)

A rarely seen butterfly species, the large swallowtail butterfly Papilio elwesi Leech, 1889 (Lepidoptera: Papilionidae), endemic to the Chinese mainland, has been declared a state-protected animal in China since 2000, but its genome is not yet available. To obtain high-quality genome assembly and annotation, we sequenced the genome and transcriptome of P. elwesi using the PacBio and PromethION platforms, respectively. The final assembled genome was 358.51 Mb, of which 97.59% was anchored to chromosomes (30 autosomes and 1 Z sex chromosome), with a contig/scaffold N50 length of 6.79/12.32 Mb and 99.0% (n = 1367) BUSCO completeness. The genome annotation pointed to 36.82% (131.99 Mb) repetitive elements and 1296 non-coding RNAs in the genome, along with 13,681 protein-coding genes that cover 98.6% (1348) of the BUSCO genes. Among the 11,499 identified gene families, 104 underwent significantly rapid expansions or contractions, and these rapidly expanding families play roles in detoxification and metabolism. Additionally, strong synteny exists between the chromosomes of P. elwesi and P. machaon. The chromosome-level genome of P. elwesi could serve as an important genomic resource for furthering our understanding of butterfly evolution and for more in-depth genomic analyses.

The mitochondrial genomes of the Geometroidea (Lepidoptera) and their phylogenetic implications

The Geometroidea is a large superfamily of Lepidoptera in species composition and contains numerous economically important pest species that cause great loss in crop and forest production. However, understanding of mitogenomes remains limited due to relatively fewer mitogenomes previously reported for this megadiverse group. Here, we sequenced and annotated nine mitogenomes for Geometridae and further analyzed the mitogenomic evolution and phylogeny of the whole superfamily. All nine mitogenomes contained 37 mitochondrial genes typical in insects, and gene organization was conserved except for Somatina indicataria. In S. indicataria, the positions of two tRNAs were rearranged. The trnR was located before trnA instead of after trnA typical in Lepidoptera, whereas the trnE was detected rarely on the minority strand (N-strand). This trnR-trnA-trnN-trnS1-trnE-trnF newly recognized in S. indicataria represents the first gene rearrangement reported for Geometroidea and is also unique in Lepidoptera. Besides, nucleotide composition analyses showed little heterogeneity among the four geometrid subfamilies involved herein, and overall, nad6 and atp8 have higher nucleotide diversity and Ka/Ks rate in Geometridae. In addition, the taxonomic assignments of the nine species, historically defined by morphological studies, were confirmed by various phylogenetic analyses based on the hitherto most extensive mitogenomic sampling in Geometroidea.

Characterization of the complete mitochondrial genome sequence of Smerinthus caecus (Lepidoptera: Sphingidae)

In this study, we sequenced and analyzed the complete mitogenome of Smerinthus caecus Ménétriés, 1857. The mitogenome of S. caecus is a circular structure, and 15,363 bp long in size and encodes 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and a control region (CR). An extremely high AT bias of 79.2% was found in the nucleotide composition of mitogenome. Most of the PCGs used ATN as the start codon and TAA or TAG as the stop codon, which is similar to most other insect mitogenomes, except cox1, which starts with CGA. The phylogeny of Smerinthinae was reconstructed using a maximum-likelihood method, a total of 33 mitogenomes were sampled for phylogenetic analyses. The subfamily Langiinae was selected as outgroup. The results confirmed the position of S. caecus in the Smerinthinae, in which Smerinthus caecus was placed as the sister taxon to Smerinthus planus, then to Laothoe amurensis.

The Prmt5-Vasa module is essential for spermatogenesis in Bombyx mori

In lepidopteran insects, dichotomous spermatogenesis produces eupyrene spermatozoa, which are nucleated, and apyrene spermatozoa, which are anucleated. Both sperm morphs are essential for fertilization, as eupyrene sperm fertilize the egg, and apyrene sperm is necessary for the migration of eupyrene sperm. In Drosophila, Prmt5 acts as a type II arginine methyltransferase that catalyzes the symmetrical dimethylation of arginine residues in the RNA helicase Vasa. Prmt5 is critical for the regulation of spermatogenesis, but Vasa is not. To date, functional genetic studies of spermatogenesis in the lepidopteran model Bombyx mori has been limited. In this study, we engineered mutations in BmPrmt5 and BmVasa through CRISPR/Cas9-based gene editing. Both BmPrmt5 and BmVasa loss-of-function mutants had similar male and female sterility phenotypes. Through immunofluorescence staining analysis, we found that the morphs of sperm from both BmPrmt5 and BmVasa mutants have severe defects, indicating essential roles for both BmPrmt5 and BmVasa in the regulation of spermatogenesis. Mass spectrometry results identified that R35, R54, and R56 of BmVasa were dimethylated in WT while unmethylated in BmPrmt5 mutants. RNA-seq analyses indicate that the defects in spermatogenesis in mutants resulted from reduced expression of the spermatogenesis-related genes, including BmSxl, implying that BmSxl acts downstream of BmPrmt5 and BmVasa to regulate apyrene sperm development. These findings indicate that BmPrmt5 and BmVasa constitute an integral regulatory module essential for spermatogenesis in B. mori.

Diversity, duplication, and genomic organization of homeobox genes in Lepidoptera

Homeobox genes encode transcription factors with essential roles in patterning and cell fate in developing animal embryos. Many homeobox genes, including Hox and NK genes, are arranged in gene clusters, a feature likely related to transcriptional control. Sparse taxon sampling and fragmentary genome assemblies mean that little is known about the dynamics of homeobox gene evolution across Lepidoptera or about how changes in homeobox gene number and organization relate to diversity in this large order of insects. Here we analyze an extensive data set of high-quality genomes to characterize the number and organization of all homeobox genes in 123 species of Lepidoptera from 23 taxonomic families. We find most Lepidoptera have around 100 homeobox loci, including an unusual Hox gene cluster in which the lab gene is repositioned and the ro gene is next to pb A topologically associating domain spans much of the gene cluster, suggesting deep regulatory conservation of the Hox cluster arrangement in this insect order. Most Lepidoptera have four Shx genes, divergent zen-derived loci, but these loci underwent dramatic duplication in several lineages, with some moths having over 165 homeobox loci in the Hox gene cluster; this expansion is associated with local LINE element density. In contrast, the NK gene cluster content is more stable, although there are differences in organization compared with other insects, as well as major rearrangements within butterflies. Our analysis represents the first description of homeobox gene content across the order Lepidoptera, exemplifying the potential of newly generated genome assemblies for understanding genome and gene family evolution.

Current Scenario of Exogenously Induced RNAi for Lepidopteran Agricultural Pest Control: From dsRNA Design to Topical Application

Invasive insects cost the global economy around USD 70 billion per year. Moreover, increasing agricultural insect pests raise concerns about global food security constraining and infestation rising after climate changes. Current agricultural pest management largely relies on plant breeding-with or without transgenes-and chemical pesticides. Both approaches face serious technological obsolescence in the field due to plant resistance breakdown or development of insecticide resistance. The need for new modes of action (MoA) for managing crop health is growing each year, driven by market demands to reduce economic losses and by consumer demand for phytosanitary measures. The disabling of pest genes through sequence-specific expression silencing is a promising tool in the development of environmentally-friendly and safe biopesticides. The specificity conferred by long dsRNA-base solutions helps minimize effects on off-target genes in the insect pest genome and the target gene in non-target organisms (NTOs). In this review, we summarize the status of gene silencing by RNA interference (RNAi) for agricultural control. More specifically, we focus on the engineering, development and application of gene silencing to control Lepidoptera through non-transforming dsRNA technologies. Despite some delivery and stability drawbacks of topical applications, we reviewed works showing convincing proof-of-concept results that point to innovative solutions. Considerations about the regulation of the ongoing research on dsRNA-based pesticides to produce commercialized products for exogenous application are discussed. Academic and industry initiatives have revealed a worthy effort to control Lepidoptera pests with this new mode of action, which provides more sustainable and reliable technologies for field management. New data on the genomics of this taxon may contribute to a future customized target gene portfolio. As a case study, we illustrate how dsRNA and associated methodologies could be applied to control an important lepidopteran coffee pest.

Single Night Surveys of Moth Communities Can Serve as Ultra-Rapid Biodiversity Assessments

Biodiversity conservation decisions are typically based on limited data and resources. For this reason, there is great interest in surveying taxa that may allow for a rapid assessment of the biodiversity at a site. Numerous taxa have been proposed and utilized for rapid assessments that allow for such a survey in a matter of weeks or less. Herein, we test the idea that nocturnal moths have many of the characteristics that make them ideal for such surveys, such as relative ease of identification, strong ecological association with specific plant species and habitats, high alpha diversity, extended seasonal activity, and ease of trapping. We demonstrate that even in a few hours of sampling during single night surveys, moth communities are predictive of regional forest types at sampling sites in New Jersey. We sampled moths in five different forest habitats in New Jersey, USA: Pine Barrens, Upland Deciduous Forest, Palustrine Deciduous Forest, Maritime Forest, and Ruderal/Disturbed Forests, at four sites per forest type. Non-metric multidimensional scaling (NMDS) analyses revealed that moth communities differ significantly across these four forest types (p < 0.01). We used Analysis of Similarity (ANOSIM) R tests to quantify the degree of differentiation among moth communities, and found that Tortricidae (R = 0.657) and Geometridae (R = 0.637) predict forest communities nearly as well as the total moth diversity (R = 0.668). Uncommon species (R = 0.665) were better predictors than common species (R = 0.500). Host plant generalists (R = 0.654) were better predictors than specialists (0.538), which was a surprising find.

Cretaceous lophocoronids with short proboscis and retractable female genitalia provide the earliest evidence for their feeding and oviposition habits

We describe two new species of Lophocoronidae: Acanthocorona hedida Zhang, Shih and Engel sp. n. and Acanthocorona venulosa Zhang, Shih and Engel sp. n., and an undetermined specimen from mid-Cretaceous Kachin amber. Phylogenetic analysis of basal lepidopteran lineages, including three extinct families, was undertaken. The analysis supported monophyly of Glossata although internal relationships remain controversial. Acanthocorona and Lophocorona form a monophyletic group. It is likely that short and simply structured proboscides of Acanthocorona were used to sip water droplets, pollination drops from gymnosperms, nectar from early flowers, or sap from injured leaves. Both retracted and extended ovipositors are preserved in the material reported here, revealing their morphology and indicating that these Cretaceous lophocoronids inserted eggs into the tissues of their host plants.

Evolutionary functional morphology of the proboscis and feeding apparatus of hawk moths (Sphingidae: Lepidoptera)

The morphology of the proboscis and associated feeding organs was studied in several nectar-feeding hawk moths, as well as a specialized honey-feeder and two supposedly nonfeeding species. The proboscis lengths ranged from a few millimeters to more than 200 mm. Despite the variation in proboscis length and feeding strategy, the principle external and internal composition of the galeae, the stipes pump, and the suction pump were similar across all species. The morphology of the smooth and slender proboscis is highly conserved among all lineages of nectar-feeding Sphingidae. Remarkably, they share a typical arrangement of the sensilla at the tip. The number and length of sensilla styloconica are independent from proboscis length. A unique proboscis morphology was found in the honey-feeding species Acherontia atropos. Here, the distinctly pointed apex displays a large subterminal opening of the food canal, and thus characterizes a novel type of piercing proboscis in Lepidoptera. In the probably nonfeeding species, the rudimentary galeae are not interlocked and the apex lacks sensilla styloconica; galeal muscles, however, are present. All studied species demonstrate an identical anatomy of the stipes, and suction pump, regardless of proboscis length and diet. Even supposedly nonfeeding Sphingidae possess all organs of the feeding apparatus, suggesting that their proboscis rudiments might still be functional. The morphometric analyses indicate significant positive correlations between galea lumen volume and stipes muscle volume as well as the volume of the food canal and the muscular volume of the suction pump. Size correlations of these functionally connected organs reflect morphological fine-tuning in the evolution of proboscis length and function.

Characterization of Seventeen Complete Mitochondrial Genomes: Structural Features and Phylogenetic Implications of the Lepidopteran Insects

Lepidoptera (moths and butterflies) are widely distributed in the world, but high-level phylogeny in Lepidoptera remains uncertain. More mitochondrial genome (mitogenome) data can help to conduct comprehensive analysis and construct a robust phylogenetic tree. Here, we sequenced and annotated 17 complete moth mitogenomes and made comparative analysis with other moths. The gene order of trnM-trnI-trnQ in 17 moths was different from trnI-trnQ-trnM of ancestral insects. The number, type, and order of genes were consistent with reported moths. The length of newly sequenced complete mitogenomes ranged from 14,231 bp of Rhagastis albomarginatus to 15,756 bp of Numenes albofascia. These moth mitogenomes were typically with high A+T contents varied from 76.0% to 81.7% and exhibited negative GC skews. Among 13 protein coding genes (PCGs), some unusual initiations and terminations were found in part of newly sequenced moth mitogenomes. Three conserved gene-overlapping regions and one conserved intergenic region were detected among 17 mitogenomes. The phylogenetic relationship of major superfamilies in Macroheterocera was as follows: (Bombycoidea + Lasiocampoidea) + ((Drepanoidea + Geometroidea) + Noctuoidea)), which was different from previous studies. Moreover, the topology of Noctuoidea as (Notodontidae + (Erebidae + Noctuidae)) was supported by high Bayesian posterior probabilities (BPP = 1.0) and bootstrapping values (BSV = 100). This study greatly enriched the mitogenome database of moth and strengthened the high-level phylogenetic relationships of Lepidoptera.

Enhanced Resolution of Evolution and Phylogeny of the Moths Inferred from Nineteen Mitochondrial Genomes

The vast majority (approximately 90%) of Lepidoptera species belong to moths whose phylogeny has been widely discussed and highly controversial. For the further understanding of phylogenetic relationships of moths, nineteen nearly complete mitochondrial genomes (mitogenomes) of moths involved in six major lineages were sequenced and characterized. These mitogenomes ranged from 15,177 bp (Cyclidia fractifasciata) to 15,749 bp (Ophthalmitis albosignaria) in length, comprising of the core 37 mitochondrial genes (13 protein-coding genes (PCGs) + 22 tRNAs + two rRNAs) and an incomplete control region. The order and orientation of genes showed the same pattern and the gene order of trnM-trnI-trnQ showed a typical rearrangement of Lepidoptera compared with the ancestral order of trnI-trnQ-trnM. Among these 13 PCGs, ATP8 exhibited the fastest evolutionary rate, and Drepanidae showed the highest average evolutionary rate among six families involved in 66 species. The phylogenetic analyses based on the dataset of 13 PCGs suggested the relationship of (Notodontidae + (Noctuidae + Erebidae)) + (Geometridae + (Sphingidae + Drepanidae)), which suggested a slightly different pattern from previous studies. Most groups were well defined in the subfamily level except Erebidae, which was not fully consistent across bayesian and maximum likelihood methods. Several formerly unassigned tribes of Geometridae were suggested based on mitogenome sequences despite a not very strong support in partial nodes. The study of mitogenomes of these moths can provide fundamental information of mitogenome architecture, and the phylogenetic position of moths, and contributes to further phylogeographical studies and the biological control of pests.

Early diversifications of angiosperms and their insect pollinators: were they unlinked?

The present-day ubiquity of angiosperm-insect pollination has led to the hypothesis that these two groups coevolved early in their evolutionary history. However, recent fossil discoveries and fossil-calibrated molecular dating analyses challenge the notion that early diversifications of angiosperms and insects were inextricably linked. In this article, we examine (i) the discrepancies between dates of emergence for angiosperms and major clades of insects; (ii) the long history of gymnosperm-insect pollination modes, which likely shaped early angiosperm-insect pollination mutualisms; and (iii) how the K-Pg (Cretaceous-Paleogene) mass extinction event was vital in propelling modern angiosperm-insect mutualisms. We posit that the early diversifications of angiosperms and their insect pollinators were largely decoupled until the end of the Cretaceous.

Comparative mitochondrial genome analysis and phylogenetic relationship among lepidopteran species

Lepidoptera has rich species including many agricultural pests and economical insects around the world. The mitochondrial genomes (mitogenomes) were utilized to explore the phylogenetic relationships between difference taxonomic levels in Lepidoptera. However, the knowledge of mitogenomic characteristics and phylogenetic position about superfamily-level in this order is unresolved. In this study, we integrated 794 mitogenomes consisting of 37 genes and a noncoding control region, which covered 26 lepidopteran superfamilies from newly sequenced and publicly available genomes for comparative genomic and phylogenetic analysis. In primitive taxon, putative start codon of cox1 gene was ATA or ATT instead of CGA, but stop codon of that showed four types, namely TAA, TAG, TA and T. The 7-bp overlap between atp8 and atp6 presented as "ATGATAA". Moreover, the most frequently utilized amino acids were leucine (UUA) in 13 PCGs. Phylogenetic analysis showed that the main backbone relationship in Lepidoptera was (Hepialoidea + (Nepticuloidea + (Adeloidea + (Tischerioidea + (Tineoidea + (Yponomeutoidea + (Gracillarioidea + (Papilionoidea + ((Zygaenoidea + Tortricoidea) + (Gelechioidea + (Pyraloidea + ((Geometroidea + Noctuoidea) + (Lasiocampoidea + Bombycoidea))))))))))))).

Molecular tug-of-war: Plant immune recognition of herbivory

Plant defense responses against insect herbivores are induced through wound-induced signaling and the specific perception of herbivore-associated molecular patterns (HAMPs). In addition, herbivores can deliver effectors that suppress plant immunity. Here we review plant immune recognition of HAMPs and effectors, and argue that these initial molecular interactions upon a plant-herbivore encounter mediate and structure effective resistance. While the number of distinct HAMPs and effectors from both chewing and piercing-sucking herbivores has expanded rapidly with omics-enabled approaches, paired receptors and targets in the host are still not well characterized. Herbivore-derived effectors may also be recognized as HAMPs depending on the host plant species, potentially through the evolution of novel immune receptor functions. We compile examples of HAMPs and effectors where natural variation between species may inform evolutionary patterns and mechanisms of plant-herbivore interactions. Finally, we discuss the combined effects of wounding and HAMP recognition, and review potential signaling hubs, which may integrate both sensing functions. Understanding the precise mechanisms for plant sensing of herbivores will be critical for engineering resistance in agriculture.

Effects of Host Plant and Insect Generation on Shaping of the Gut Microbiota in the Rice Leaffolder, Cnaphalocrocis medinalis

Gut microbes in insects may play an important role in the digestion, immunity and protection, detoxification of toxins, development, and reproduction. The rice leaffolder Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Crambidae) is a notorious insect pest that can damage rice, maize, and other gramineous plants. To determine the effects of host plants and generations on the gut microbiota of C. medinalis, we deciphered the bacterial configuration of this insect pest fed rice or maize for three generations by Illumina MiSeq technology. A total of 16 bacterial phyla, 34 classes, 50 orders, 101 families, 158 genera, and 44 species were identified in C. medinalis fed rice or maize for three generations. Host plants, insect generation, and their interaction did not influence the alpha diversity indices of the gut microbiota of C. medinalis. The dominant bacterial taxa were Proteobacteria and Firmicutes at the phylum level and Enterococcus and unclassified Enterobacteriaceae at the genus level. A number of twenty genera coexisted in the guts of C. medinalis fed rice or maize for three generations, and their relative abundances occupied more than 90% of the gut microbiota of C. medinalis. A number of two genera were stably found in the gut of rice-feeding C. medinalis but unstably found in the gut microbiota of maize-feeding C. medinalis, and seven genera were stably found in the gut of maize-feeding C. medinalis but unstably found in the gut of rice-feeding C. medinalis. In addition, many kinds of microbes were found in some but not all samples of the gut of C. medinalis fed on a particular host plant. PerMANOVA indicated that the gut bacteria of C. medinalis could be significantly affected by the host plant and host plant × generation. We identified 47 taxa as the biomarkers for the gut microbiota of C. medinalis fed different host plants by LEfSe. Functional prediction suggested that the most dominant role of the gut microbiota in C. medinalis is metabolism, followed by environmental information processing, cellular processes, and genetic information processing. Our findings will enrich the understanding of gut bacteria in C. medinalis and reveal the differences in gut microbiota in C. medinalis fed on different host plants for three generations.

Macrostructural Evolution of the Mitogenome of Butterflies (Lepidoptera, Papilionoidea)

Simple Summary

Papilionoidea is a superfamily of Lepidoptera encompassing about 19,000 species. In the present work, we study the evolution of the structure of the mitogenome of these lepidopterans. The mechanisms generating the eight arrangements known for Papilionoidea were investigated analysing the movements of different mitochondrial genes. Five newly sequenced/assembled mitogenomes were included in our analysis involving more than 600 genomes. We provide new findings that help to understand the evolution of the gene orders MIQGO, IMQGO, 2S1GO, ES1GO and S1NGO in different butterflies. We demonstrate that the evolution of the 2S1GO in Lycaenidae followed a complicated pathway with multiple events of duplication and loss of trnS1 and changes in anticodon. We describe two new gene orders 2FFGO and 4QGO for Ampittia subvittatus (Hesperiidae) and Bhutanitis thaidina (Papilionidae).

Abstract

The mitogenome of the species belonging to the Papilionodea (Lepidoptera) is a double stranded circular molecule containing the 37 genes shared by Metazoa. Eight mitochondrial gene orders are known in the Papilionoidea. MIQGO is the plesiomorphic gene order for this superfamily, while other mitochondrial arrangements have a very limited distribution. 2S1GO gene order is an exception and is present in several Lycaenidae and one species of Hesperiidae. We studied the macrostructural changes generating the gene orders of butterflies by analysing a large data set (611 taxa) containing 5 new mitochondrial sequences/assemblies and 87 de novo annotated mitogenomes. Our analysis supports a possible origin of the intergenic spacer trnQ-nad2, characterising MIQGO, from trnM. We showed that the homoplasious gene order IMQGO, shared by butterflies, species of ants, beetles and aphids, evolved through different transformational pathways. We identify a complicated evolutionary scenario for 2S1GO in Lycaenidae, characterised by multiple events of duplication/loss and change in anticodon of trnS1. We show that the gene orders ES1GO and S1NGO originated through a tandem duplication random loss mechanism. We describe two novel gene orders. Ampittia subvittatus (Hesperiidae) exhibits the gene order 2FFGO, characterised by two copies of trnF, one located in the canonical position and a second placed in the opposite strand between trnR and trnN. Bhutanitis thaidina (Papilionidae) exhibits the gene order 4QGO, characterised by the quadruplication of trnQ.

Ecological Infrastructures May Enhance Lepidopterans Predation in Irrigated Mediterranean Farmland, Depending on Their Typology and the Predator Guild

Ecological infrastructures (EIs) are considered relevant components in agricultural landscapes to support biodiversity and ecosystem services. We used the predatory attacks on lepidopteran dummies as a proxy to assess predation rates in the agricultural matrix and different EIs types according to their location and vegetation structure. We aimed at comparing the effect of different types of EI on the predation intensity in two intensively irrigated agricultural areas located in the Sorraia and Tagus river valleys in central Portugal. We hypothesized that: (1) the predation rate would be higher near EIs compared with the agricultural matrix, (2) the positive effect of EIs on predation rate would differ with their typologies, and (3) the EIs’ proximity and proportion in the surrounding landscape would have a positive effect on the predation rate in agricultural fields. The EI typologies influenced differently the predator groups and the overall predation rate. Major differences were observed for bird predation, being higher in woody EIs. A positive correlation between predation rate and EIs area of the surrounding landscape, as well as a negative correlation with the distance to the nearest riparian and woody EIs, was observed for birds. The observed dissimilarities in the predators’ response may be related to habitat differences and its functional connectivity. The overall monthly low predation rates are possibly related to the intensive agricultural system and the small area occupied by EIs.

The Angiosperm Terrestrial Revolution and the origins of modern biodiversity

Biodiversity today has the unusual property that 85% of plant and animal species live on land rather than in the sea, and half of these live in tropical rainforests. An explosive boost to terrestrial diversity occurred from c. 100-50 million years ago, the Late Cretaceous and early Palaeogene. During this interval, the Earth-life system on land was reset, and the biosphere expanded to a new level of productivity, enhancing the capacity and species diversity of terrestrial environments. This boost in terrestrial biodiversity coincided with innovations in flowering plant biology and evolutionary ecology, including their flowers and efficiencies in reproduction; coevolution with animals, especially pollinators and herbivores; photosynthetic capacities; adaptability; and ability to modify habitats. The rise of angiosperms triggered a macroecological revolution on land and drove modern biodiversity in a secular, prolonged shift to new, high levels, a series of processes we name here the Angiosperm Terrestrial Revolution.

Expanding the Menu: Are Polyphagy and Gene Family Expansions Linked across Lepidoptera?

Evolutionary expansions and contractions of gene families are often correlated with key innovations and/or ecological characteristics. In butterflies and moths (Lepidoptera), expansions of gene families involved in detoxification of plant specialized metabolites are hypothesized to facilitate a polyphagous feeding style. However, analyses supporting this hypothesis are mostly based on a limited number of lepidopteran species. We applied a phylogenomics approach, using 37 lepidopteran genomes, to analyze if gene family evolution (gene gain and loss) is associated with the evolution of polyphagy. Specifically, we compared gene counts and evolutionary gene gain and loss rates of gene families involved in adaptations with plant feeding. We correlated gene evolution to host plant family range (phylogenetic diversity) and specialized metabolite content of plant families (functional metabolite diversity). We found a higher rate for gene loss than gene gain in Lepidoptera, a potential consequence of genomic rearrangements and deletions after (potentially small-scale) duplication events. Gene family expansions and contractions varied across lepidopteran families, and were associated to host plant use and specialization levels. Within the family Noctuidae, a higher expansion rate for gene families involved in detoxification can be related to the large number of polyphagous species. However, gene family expansions are observed in both polyphagous and monophagous lepidopteran species and thus seem to be species-specific in the taxa sampled. Nevertheless, a significant positive correlation of gene counts of the carboxyl- and choline esterase and glutathione-S-transferase detoxification gene families with the level of polyphagy was identified across Lepidoptera.

Transcriptome analysis identifies candidate genes in the biosynthetic pathway of sex pheromones from a zygaenid moth, Achelura yunnanensis (Lepidoptera: Zygaenidae)

In most moth species, sex pheromones responsible for mating and communication of both sexes are primarily produced by the pheromone glands (PGs) of female moths. Although the PG transcriptomes and pheromone production related genes from 24 moth species have been characterized, studies on the related information remain unknown in the Zygaenidae family. Here, we sequenced the PG transcriptome of a zygaenid moth, Achelura yunnanensis. Such the sequencing resulted in the yields of 47,632,610 clean reads that were assembled into 54,297 unigenes, coupled with RNA sequencing data from 12 other tissues. Based on the transcriptome, a total of 191 genes encoding pheromone biosynthesis and degradation enzymes were identified, 161 of which were predicted to have full-length sequences. A comparative analysis among 24 moth species of nine families indicated that the numbers of the genes were variable, ranging from 14 in two Grapholita species to 191 in A. yunnanensis. Phylogenetic analysis in parallel with the expression data highlighted some key genes, including three △9 and four △11 desaturases, four fatty acyl-CoA reductases (FARs) clustering in the pgFAR clade, and three significantly antennae-enriched aldehyde oxidases. An extensive tissue- and sex- expression profile revealed a broad distribution of the genes, in which 128 relatives were detected in the PGs and 127 in the antennae. This study reports, for the first time, the gene repertoires associated with the pheromone production in Zygaenidae, and provides a valuable resource for exploring putative roles of the PG-enriched genes in A. yunnanensis.

Identifying two moth species (Lepidoptera: Ditrysia) from Saudi Arabia using mitochondrial 16S rRNA sequences

The mitochondrial genetic markers are considered useful tools for discrimination between more closely related lepidopteran taxa. Therefore, the present study aimed to investigate the role of mitochondrial (mt) 16 s rRNA gene in the determination of the taxonomic position for two moth species within Ditrysia clade. Maximum likelihood analysis has indicated a well-supported dendrogram based on the Tamura-Nei model for the recovered lepidopterans. The mt 16 s rRNA query sequences from 24 species within seven families were analyzed. This analysis and bootstrap confidence revealed two major clades representing Glossata suborder within Lepidoptera, with a close relationship of Noctuoidea + (Pyraloidea (Hesperioidea + Papilionoidea)). The subfamily Heliothinae forming a sister group with Risobinae (Noctinae + Hadeninae). In addition, there is a clear observation about the close relation between Phycitinae + Galleriinae within Pyraloidea and Cyrestinae + Limenitidinae within Papilionoidea. The present study supported that the Helicoverpa and Meroptera species are the first accounts of these genera inhabiting Saudi Arabia.

The Circadian Clock in Lepidoptera

With approximately 160,000 identified species of butterflies and moths, Lepidoptera are among the most species-rich and diverse insect orders. Lepidopteran insects have fundamental ecosystem functions as pollinators and valuable food sources for countless animals. Furthermore, Lepidoptera have a significant impact on the economy and global food security because many species in their larval stage are harmful pests of staple food crops. Moreover, domesticated species such as the silkworm Bombyx mori produce silk and silk byproducts that are utilized by the luxury textile, biomedical, and cosmetics sectors. Several Lepidoptera have been fundamental as model organisms for basic biological research, from formal genetics to evolutionary studies. Regarding chronobiology, in the 1970s, Truman's seminal transplantation experiments on different lepidopteran species were the first to show that the circadian clock resides in the brain. With the implementation of molecular genetics, subsequent studies identified key differences in core components of the molecular circadian clock of Lepidoptera compared to the dipteran Drosophila melanogaster, the dominant insect species in chronobiological research. More recently, studies on the butterfly Danaus plexippus have been fundamental in characterizing the interplay between the circadian clock and navigation during the seasonal migration of this species. Moreover, the advent of Next Generation Omic technologies has resulted in the production of many publicly available datasets regarding circadian clocks in pest and beneficial Lepidoptera. This review presents an updated overview of the molecular and anatomical organization of the circadian clock in Lepidoptera. We report different behavioral circadian rhythms currently identified, focusing on the importance of the circadian clock in controlling developmental, mating and migration phenotypes. We then describe the ecological importance of circadian clocks detailing the complex interplay between the feeding behavior of these organisms and plants. Finally, we discuss how the characterization of these features could be useful in both pest control, and in optimizing rearing of beneficial Lepidoptera.

The mitochondrial genomes of Tortricidae: nucleotide composition, gene variation and phylogenetic performance

BACKGROUND

Mitochondrial genomes (mitogenomes) have greatly improved our understanding of the backbone phylogeny of Lepidoptera, but few studies on comparative mitogenomics below the family level have been conducted. Here, we generated 13 mitogenomes of eight tortricid species, reannotated 27 previously reported mitogenomes, and systematically performed a comparative analysis of nucleotide composition, gene variation and phylogenetic performance.

RESULTS

The lengths of completely sequenced mitogenomes ranged from 15,440 bp to 15,778 bp, and the gene content and organization were conserved in Tortricidae and typical for Lepidoptera. Analyses of AT-skew and GC-skew, the effective number of codons and the codon bias index all show a base bias in Tortricidae, with little heterogeneity among the major tortricid groups. Variations in the divergence rates among 13 protein-coding genes of the same tortricid subgroup and of the same PCG among tortricid subgroups were detected. The secondary structures of 22 transfer RNA genes and two ribosomal RNA genes were predicted and comparatively illustrated, showing evolutionary heterogeneity among different RNAs or different regions of the same RNA. The phylogenetic uncertainty of Enarmoniini in Tortricidae was confirmed. The synonymy of Bactrini and Olethreutini was confirmed for the first time, with the representative Bactrini consistently nesting in the Olethreutini clade. Nad6 exhibits the highest phylogenetic informativeness from the root to the tip of the resulting tree, and the combination of the third coding positions of 13 protein-coding genes shows extremely high phylogenetic informativeness.

CONCLUSIONS

This study presents 13 mitogenomes of eight tortricid species and represents the first detailed comparative mitogenomics study of Tortricidae. The results further our understanding of the evolutionary architectures of tortricid mitogenomes and provide a basis for future studies of population genetics and phylogenetic investigations in this group.

Food Plant Shifts Drive the Diversification of Sack-Bearer Moths

AbstractLepidoptera are a highly diverse group of herbivorous insects; however, some superfamilies have relatively few species. Two alternative hypotheses for drivers of Lepidoptera diversity are shifts in food plant use or shifts from concealed to external feeding as larvae. Many studies address the former hypothesis but with bias toward externally feeding taxa. One of the most striking examples of species disparity between sister lineages in Lepidoptera is between the concealed-feeding sack-bearer moths (Mimallonoidea), which contain about 300 species, and externally feeding Macroheterocera, which have over 74,000 species. We provide the first dated tree of Mimallonidae to understand the diversification dynamics of these moths in order to fill a knowledge gap pertaining to drivers of diversity within an important concealed-feeding clade. We find that Mimallonidae is an ancient Lepidoptera lineage that originated in the Cretaceous ∼105 million years ago and has had a close association with the plant order Myrtales for the past 40 million years. Diversification dynamics are tightly linked with food plant usage in this group. Reliance on Myrtales may have influenced diversification of Mimallonidae because clades that shifted away from the ancestral condition of feeding on Myrtales have the highest speciation rates in the family.

Active behaviour of terrestrial caterpillars on the water surface

Most butterfly and moth larvae (Lepidoptera) are terrestrial. When terrestrial caterpillars accidentally fall into water, they may drown or be preyed upon by aquatic predators before they can safely reach land. However, how terrestrial caterpillars escape aquatic environments and predators remains unclear. In July 2018, we observed a terrestrial caterpillar actively moving forward on the surface of a pond in Japan until it successfully reached the shore. To further investigate this behaviour in terrestrial caterpillars, we experimentally placed larvae of 13 moth species (four families) on a water surface under laboratory and field conditions. All caterpillars floated. Larvae of seven species moved forward on the water surface, whereas those of six species did not. A total of two types of behaviour were observed; in Dinumma deponens, Hypopyra vespertilio, Spirama retorta, Laelia coenosa, Lymantria dispar (all Erebidae), and Naranga aenescens (Noctuidae), larvae swung their bodies rapidly from side to side to propel themselves along the water surface (i.e., undulatory behaviour); in contrast, larvae of Acosmetia biguttula (Noctuidae) rapidly moved the abdomen (posterior segments) up and down for propulsion along the water surface (i.e., flick behaviour). Although thoracic legs were not used for undulatory and flick behaviour, rapid movements of the abdomen were used to propel caterpillars on the water surface. We also observed that undulatory and flick behaviour on the water surface aided caterpillars in escaping aquatic predators under field conditions. In addition, we investigated the relationship between body size and undulatory behaviour on the water surface in the erebid S. retorta under laboratory conditions. The frequency and speed of forward movement on the water surface increased with body length. Together, these results show that the rapid movement of elongated bodies results in forward propulsion on the water surface, allowing some terrestrial caterpillars to avoid drowning or aquatic predators. We further suggested potential factors related to morphology, host plant habitat, and defensive behaviour that may have led to the acquisition of aquatic behaviour in terrestrial caterpillars.

First Annotated Genome of a Mandibulate Moth, Neomicropteryx cornuta, Generated Using PacBio HiFi Sequencing

We provide a new, annotated genome assembly of Neomicropteryx cornuta, a species of the so-called mandibulate archaic moths (Lepidoptera: Micropterigidae). These moths belong to a lineage that is thought to have split from all other Lepidoptera more than 300 Ma and are consequently vital to understanding the early evolution of superorder Amphiesmenoptera, which contains the order Lepidoptera (butterflies and moths) and its sister order Trichoptera (caddisflies). Using PacBio HiFi sequencing reads, we assembled a highly contiguous genome with a contig N50 of nearly 17 Mb. The assembled genome length of 541,115,538 bp is about half the length of the largest published Amphiesmenoptera genome (Limnephilus lunatus, Trichoptera) and double the length of the smallest (Papilio polytes, Lepidoptera). We find high recovery of universal single copy orthologs with 98.1% of BUSCO genes present and provide a genome annotation of 15,643 genes aided by resolved isoforms from PacBio IsoSeq data. This high-quality genome assembly provides an important resource for studying ecological and evolutionary transitions in the early evolution of Amphiesmenoptera.

A database and checklist of geometrid moths (Lepidoptera) from Colombia

Background

Molecular DNA sequence data allow unprecedented advances in biodiversity assessments, monitoring schemes and taxonomic works, particularly in poorly-explored areas. They allow, for instance, the sorting of material rapidly into operational taxonomic units (such as BINs - Barcode Index Numbers), sequences can be subject to diverse analyses and, with linked metadata and physical vouchers, they can be examined further by experts. However, a prerequisite for their exploitation is the construction of reference libraries of DNA sequences that represent the existing biodiversity. To achieve these goals for Geometridae (Lepidoptera) moths in Colombia, expeditions were carried out to 26 localities in the northern part of the country in 2015–2019. The aim was to collect specimens and sequence their DNA barcodes and to record a fraction of the species richness and occurrences in one of the most biodiversity-rich countries. These data are the beginning of an identification guide to Colombian geometrid moths, whose identities are currently often provisional only, being morpho species or operational taxonomic units (OTUs). Prior to the current dataset, 99 Geometridae sequences forming 44 BINs from Colombia were publicly available on the Barcode of Life Data System (BOLD), covering 20 species only.

New information

We enrich the Colombian Geometridae database significantly by including DNA barcodes, two nuclear markers, photos of vouchers and georeferenced occurrences of 281 specimens of geometrid moths from different localities. These specimens are classified into 80 genera. Analytical tools on BOLD clustered 157 of the mentioned sequences to existing BINs identified to species level, identified earlier by experts. Another 115 were assigned to BINs that were identified to genus or tribe level only. Eleven specimens did not match any existing BIN on BOLD and are, therefore, new additions to the database. It is likely that many BINs represent undescribed species. Nine short sequences (< 500bp) were not assigned to BINs, but identified to the lowest taxonomic category by expert taxonomists and with comparisons of type material photos. The released new genetic information will help to further progress the systematics of Geometridae. An illustrated catalogue of all new records allows validation of our identifications; it is also the first document of this kind for Colombian Geometridae. All specimens are deposited at the Museo de Zoología of Universidad de Sucre (MZUS), North Colombia. DNA BINs are reported in this study through dx.doi.org/10.5883/DS-GEOCO, the species occurrences are available on SIB Colombia https://sibcolombia.net/ and the Global Biodiversity Information Facility (GBIF) https://www.gbif.org/ through https://doi.org/10.15472/ucfmkh.

Evolution of a cytoplasmic determinant: evidence for the biochemical basis of functional evolution of the novel germ line regulator oskar

Germ line specification is essential in sexually reproducing organisms. Despite their critical role, the evolutionary history of the genes that specify animal germ cells is heterogeneous and dynamic. In many insects, the gene oskar is required for the specification of the germ line. However, the germ line role of oskar is thought to be a derived role resulting from co-option from an ancestral somatic role. To address how evolutionary changes in protein sequence could have led to changes in the function of Oskar protein that enabled it to regulate germ line specification, we searched for oskar orthologs in 1,565 publicly available insect genomic and transcriptomic data sets. The earliest-diverging lineage in which we identified an oskar ortholog was the order Zygentoma (silverfish and firebrats), suggesting that oskar originated before the origin of winged insects. We noted some order-specific trends in oskar sequence evolution, including whole gene duplications, clade-specific losses, and rapid divergence. An alignment of all known 379 Oskar sequences revealed new highly conserved residues as candidates that promote dimerization of the LOTUS domain. Moreover, we identified regions of the OSK domain with conserved predicted RNA binding potential. Furthermore, we show that despite a low overall amino acid conservation, the LOTUS domain shows higher conservation of predicted secondary structure than the OSK domain. Finally, we suggest new key amino acids in the LOTUS domain that may be involved in the previously reported Oskar−Vasa physical interaction that is required for its germ line role.

Lepidoptera demonstrate the relevance of Murray's Law to circulatory systems with tidal flow

BACKGROUND

Murray's Law, which describes the branching architecture of bifurcating tubes, predicts the morphology of vessels in many amniotes and plants. Here, we use insects to explore the universality of Murray's Law and to evaluate its predictive power for the wing venation of Lepidoptera, one of the most diverse insect orders. Lepidoptera are particularly relevant to the universality of Murray's Law because their wing veins have tidal, or oscillatory, flow of air and hemolymph. We examined over one thousand wings representing 667 species of Lepidoptera.

RESULTS

We found that veins with a diameter above approximately 50 microns conform to Murray's Law, with veins below 50 microns in diameter becoming less and less likely to conform to Murray's Law as they narrow. The minute veins that are most likely to deviate from Murray's Law are also the most likely to have atrophied, which prevents efficient fluid transport regardless of branching architecture. However, the veins of many taxa continue to branch distally to the areas where they atrophied, and these too conform to Murray's Law at larger diameters (e.g., Sesiidae).

CONCLUSIONS

This finding suggests that conformity to Murray's Law in larger taxa may reflect requirements for structural support as much as fluid transport, or may indicate that selective pressures for fluid transport are stronger during the pupal stage-during wing development prior to vein atrophy-than the adult stage. Our results increase the taxonomic scope of Murray's Law and provide greater clarity about the relevance of body size.

Gut Bacterial Communities of Lymantria xylina and Their Associations with Host Development and Diet

The gut microbiota of insects has a wide range of effects on host nutrition, physiology, and behavior. The structure of gut microbiota may also be shaped by their environment, causing them to adjust to their hosts; thus, the objective of this study was to examine variations in the morphological traits and gut microbiota of Lymantria xylina in response to natural and artificial diets using high-throughput sequencing. Regarding morphology, the head widths for larvae fed on a sterilized artificial diet were smaller than for larvae fed on a non-sterilized host-plant diet in the early instars. The gut microbiota diversity of L. xylina fed on different diets varied significantly, but did not change during different development periods. This seemed to indicate that vertical inheritance occurred in L. xylina mutualistic symbionts. Acinetobacter and Enterococcus were dominant in/on eggs. In the first instar larvae, Acinetobacter accounted for 33.52% of the sterilized artificial diet treatment, while Enterococcus (67.88%) was the predominant bacteria for the non-sterilized host-plant diet treatment. Gut microbe structures were adapted to both diets through vertical inheritance and self-regulation. This study clarified the impacts of microbial symbiosis on L. xylina and might provide new possibilities for improving the control of these bacteria.