Bioluminescence has been hypothesized as aposematic signalling, intersexual communication and a predatory strategy, but origins and relationships among bioluminescent beetles have been contentious. We reconstruct the phylogeny of the bioluminescent elateroid beetles (i.e. Elateridae, Lampyridae, Phengodidae and Rhagophthalmidae), analysing genomic data of Sinopyrophorus Bi & Li, and in light of our phylogenetic results, we erect Sinopyrophoridae Bi & Li, stat.n. as a clicking elaterid‐like sister group of the soft‐bodied bioluminescent elateroid beetles, that is, Lampyridae, Phengodidae and Rhagophthalmidae. We suggest a single origin of bioluminescence for these four families, designated as the ‘lampyroid clade’, and examine the origins of bioluminescence in the terminal lineages of click beetles (Elateridae). The soft‐bodied bioluminescent lineages originated from the fully sclerotized elateroids as a derived clade with clicking Sinopyrophorus and Elateridae as their serial sister groups. This relationship indicates that the bioluminescent soft‐bodied elateroids are modified click beetles. We assume that bioluminescence was not present in the most recent common ancestor of Elateridae and the lampyroid clade and it evolved among this group with some delay, at the latest in the mid‐Cretaceous period, presumably in eastern Laurasia. The delimitation and internal structure of the elaterid‐lampyroid clade provides a phylogenetic framework for further studies on the genomic variation underlying the evolution of bioluminescence.

BackgroundPapilio bianor Cramer, 1777 (commonly known as the Chinese peacock butterfly) (Insecta, Lepidoptera, Papilionidae) is a widely distributed swallowtail butterfly with a wide number of geographic populations ranging from the southeast of Russia to China, Japan, India, Vietnam, Myanmar, and Thailand. Its wing color consists of both pigmentary colored scales (black, reddish) and structural colored scales (iridescent blue or green dust). A high-quality reference genome of P. bianor is an important foundation for investigating iridescent color evolution, phylogeography, and the evolution of swallowtail butterflies.FindingsWe obtained a chromosome-level de novo genome assembly of the highly heterozygous P. bianor using long Pacific Biosciences sequencing reads and high-throughput chromosome conformation capture technology. The final assembly is 421.52 Mb on 30 chromosomes (29 autosomes and 1 Z sex chromosome) with 13.12 Mb scaffold N50. In total, 15,375 protein-coding genes and 233.09 Mb of repetitive sequences were identified. Phylogenetic analyses indicated that P. bianor separated from a common ancestor of swallowtails ∼23.69–36.04 million years ago. Demographic history suggested that the population expansion of this species from the last interglacial period to the last glacial maximum possibly resulted from its decreased natural enemies and its adaptation to climate change during the glacial period.ConclusionsWe present a high-quality chromosome-level reference genome of P. bianor using long-read single-molecule sequencing and Hi-C–based chromatin interaction maps. Our results lay the foundation for exploring the genetic basis of special biological features of P. bianor and also provide a useful data source for comparative genomics and phylogenomics among butterflies and moths.

No abstract

The new subfamily Sinopyrophorinae within Elateridae is proposed to accommodate a bioluminescent species, Sinopyrophorusschimmeli Bi & Li, gen. et sp. nov., recently discovered in Yunnan, China. This lineage is morphologically distinguished from other click-beetle subfamilies by the strongly protruding frontoclypeal region, which is longitudinally carinate medially, the pretarsal claws without basal setae, the hind wing venation with a well-defined wedge cell, the abdomen with seven (male) or six (female) ventrites, the large luminous organ on the abdominal sternite II, and the male genitalia with median lobe much shorter than parameres, and parameres arcuate, with the inner margin near its apical third dentate. Molecular phylogeny based on the combined 14 mitochondrial and two nuclear genes supports the placement of this taxon far from other luminescent click-beetle groups, which provides additional evidence for the multiple origin of bioluminescence in Elateridae. Illustrations of habitus and main diagnostic features of S.schimmeli Bi & Li, gen. et sp. nov. are provided, as well as the brief description of its luminescent behavior.

Fireflies are among the most charismatic insects for their spectacular bioluminescence, but the origin and evolution of bioluminescence remain elusive. Especially, the genic basis of luciferin (d-luciferin) biosynthesis and light patterns is largely unknown. Here, we present the high-quality reference genomes of two fireflies Lamprigera yunnana (1053 Mb) and Abscondita terminalis (501 Mb) with great differences in both morphology and luminous behavior. We sequenced the transcriptomes and proteomes of luminous organs of two species. We created the CRISPR/Cas9-induced mutants of Abdominal B gene without luminous organs in the larvae of A. terminalis and sequenced the transcriptomes of mutants and wild-types. Combining gene expression analyses with comparative genomics, we propose a more complete luciferin synthesis pathway, and confirm the convergent evolution of bioluminescence in insects. Using experiments, the function of the firefly acyl-CoA thioesterase (ACOT1) to convert l-luciferin to d-luciferin was validated for the first time. Comparisons of three-dimension reconstruction of luminous organs and their differentially expressed genes among two species suggest that two positive genes in the calcium signaling pathway and structural difference of luminous organs may play an important role in the evolution of flash pattern. Altogether, our results provide important resources for further exploring bioluminescence in insects.

The leaf resemblance of Kallima (Nymphalidae) butterflies is an important ecological adaptive mechanism that increases their survival. However, the genetic mechanism underlying ecological adaptation remains unclear owing to a dearth of genomic information. Here, we determined the karyotype (n = 31) of the dead-leaf butterfly Kallima inachus, and generated a high-quality, chromosome-level assembly (568.92 Mb; contig N50: 19.20 Mb). We also identified candidate Z and W chromosomes. To our knowledge, this is the first study to report on these aspects of this species. In the assembled genome, 15,309 protein-coding genes and 49.86% repeat elements were annotated. Phylogenetic analysis showed that K. inachus diverged from Melitaea cinxia (no leaf resemblance), both of which are in Nymphalinae, around 40 million years ago. Demographic analysis indicated that the effective population size of K. inachus decreased during the last interglacial period in the Pleistocene. The wings of adults with the pigmentary gene ebony knocked out using CRISPR/Cas9 showed phenotypes in which the orange dorsal region and entire ventral surface darkened, suggesting its vital role in the ecological adaption of dead-leaf butterflies. Our results provide important genome resources for investigating the genetic mechanism underlying protective resemblance in dead-leaf butterflies and insights into the molecular basis of protective coloration. | 1081 YANG et Al.

Butterflies have been of great interest to naturalists for centuries, and the study of butterflies has been an integral part of ecology and evolution ever since Darwin proposed his theory of natural selection in 1859. There are > 18 000 butterfly species worldwide, showing great diversity in morphological traits and ecological niches. Compared with butterfly diversity, however, patterns of genome size variation in butterflies remain poorly understood, especially in a phylogenetic context. Here, we sequenced and assembled the mitogenomes of 68 butterflies and measured the genome sizes (C-values) of 67 of them. We also assembled 10 mitogenomes using reads from GenBank. Among the assembled 78 mitogenomes, those from 59 species, 23 genera and one subfamily are reported for the first time. Combining with published data of mitogenomes and genome size, we explored the patterns in genome size variation for 106 butterfly species in a phylogenetic context based on analyses of mitogenomes from 264 species covering six families. Our results show that the genome size of butterflies has a 6.4-fold variation ranging from 0.203 pg (199 Mb) (Nymphalidae: Heliconius xanthocles) to 1.287 pg (1253 Mb) (Papilionidae: Parnassius orleans). Within families, the largest variation was found in Papilionidae (5.9-fold: 0.22-1.29 pg), followed by Nymphalidae (4.8-fold: 0.2-0.95 pg), Pieridae (4.4-fold: 0.22-0.97 pg), Hesperiidae (2.2-fold: 0.3-0.66 pg), Lycaenidae (2.6-fold: 0.39-1.02 pg) and . Our data also suggest that butterflies have an ancestral genome size of c. 0.5 pg, and some ancestral genome size increase or decrease events along different subfamilies or tribes produce the diversity of genome size variation in diverse butterflies. Our data provide novel insights into patterns of genome size variation in butterflies and are an important reference for future genome sequencing programmes.

The nearly complete mitochondrial genome (mitogenome) of Sinopyrophorus schimmeli Bi et Li, the luminous click beetle recorded in Asia, is described in this study. It totalizes 15,951 bp and contains 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes, and most part of AT-rich region. Thirteen PCGs totalize 11,136 bp, start with ATN, stop with TAA/G, except for cox2 and cox3 stopping with T. The rrnL and rrnS are 1280 and 862 bp, respectively. The AT-rich region contains several structures characteristic of the Coleoptera. The phylogenetic analyses of 13 PCGs confirm the position of S. schimmeli in Elateridae.