Insect mimicry of plants dates back to the Permian

Landing force reveals new form of motion-induced sound camouflage in a wild predator

Predator-prey arms races have led to the evolution of finely tuned disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success in natural conditions. We used high-resolution movement data to quantify how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy. We hypothesized that hunting barn owls would modulate their landing force, potentially reducing noise levels in the vicinity of prey. Analysing 87,957 landings by 163 individuals equipped with GPS tags and accelerometers, we show that barn owls reduce their landing force as they approach their prey, and that landing force predicts the success of the following hunting attempt. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries. The physical environment, therefore, affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land use. Finally, hunting strike forces in barn owls were the highest recorded in any bird, relative to body mass, highlighting the range of selective pressures that act on landings and the capacity of these predators to modulate their landing force. Overall, our results provide the first measurements of landing force in a wild setting, revealing a new form of motion-induced sound camouflage and its link to hunting success.

Evolutionary genomics of camouflage innovation in the orchid mantis

The orchid mantises achieve camouflage with morphological modifications in body color and pattern, providing an interesting model for understanding phenotypic innovation. However, a reference genome is lacking for the order Mantodea. To unveil the mechanisms of plant-mimicking body coloration and patterns, we performed de novo assembly of two chromosome-level genomes of the orchid mantis and its close relative, the dead leaf mantis. Comparative genomic analysis revealed that the Scarlet gene plays an important role in the synthesis of xanthommatin, an important pigment for mantis camouflage coloration. Combining developmental transcriptomic analysis and genetic engineering experiments, we found that the cuticle was an essential component of the 'petal-like' enlargement, and specific expression in the ventral femur was controlled by Wnt signaling. The prolonged expression of Ultrabithorax (Ubx) accompanied by femoral expansion suggested that Ubx determines leg remodeling in the early developmental stage. We also found evidence of evolution of the Trypsin gene family for insectivory adaptation and ecdysone-dependent sexual dimorphism in body size. Overall, our study presents new genome catalogs and reveals the genetic and evolutionary mechanisms underlying the unique camouflage of the praying mantis, providing evolutionary developmental insights into phenotypic innovation and adaptation.

Ecological radiations of insects in the Mesozoic

The Mesozoic is a key era for the rise of the modern insect fauna. Among the most important evolutionary events in Mesozoic insects are the radiation of holometabolous insects, the origin of eusocial and parasitoid insects, diversification of pollinating insects, and development of advanced mimicry and camouflage. These events are closely associated with the diversification of insect ecological behaviors and colonization of new ecospaces. At the same time, insects had evolved more complex and closer ecological associations with various plants and animals. Mesozoic insects played a key and underappreciated ecological role in reconstructing and maintaining terrestrial ecosystems. A greater understanding of the history of insects may help to mitigate future changes in insect diversity and abundance.

Aposematic coloration from Mid-Cretaceous Kachin amber

Aposematic coloration is among the most diverse antipredator strategies, which can signal unpleasantness of organisms to potential predators and reduce the probability of predation. Unlike mimesis, aposematic coloration allows organisms to warn their predators away by conspicuous and recognizable colour patterns. However, aposematism has been a regular puzzle, especially as the long-term history of such traits is obscured by an insufficient fossil record. Here, we report the discovery of aposematic coloration in an orthopteran nymph from Mid-Cretaceous Kachin amber (99 million years old). It is attributed to the extinct family Elcanidae and erected as a new genus identified by conspicuous dark/light-striped coloration, four apical spurs on the metatibia, a two-segmented metatarsus and unsegmented stylus. It represents the first fossil orthopteran preserved with aposematic coloration from the Mesozoic, demonstrating that orthopterans had evolved aposematism by the Mid-Cretaceous. Our findings provide novel insights into the early evolution of anti-predator strategies among orthopterans. Together with mimesis, debris-carrying camouflage and aposematism previously reported, our findings demonstrate the relative complexity of prey-predator interactions in the Mesozoic, especially in the Mid-Cretaceous Kachin amber forest. This article is part of the theme issue 'The impact of Chinese palaeontology on evolutionary research'.

A twig-like insect stuck in the Permian mud indicates early origin of an ecological strategy in Hexapoda evolution

Full body impressions and resting traces of Hexapoda can be of extreme importance because they bring crucial information on behavior and locomotion of the trace makers, and help to better define trophic relationships with other organisms (predators or preys). However, these ichnofossils are much rarer than trackways, especially for winged insects. Here we describe a new full-body impression of a winged insect from the Middle Permian of Gonfaron (Var, France) whose preservation is exceptional. The elongate body with short prothorax and legs and long wings overlapping the body might suggests a plant mimicry as for some extant stick insects. These innovations are probably in relation with an increasing predation pressure by terrestrial vertebrates, whose trackways are abundant in the same layers. This discovery would possibly support the recent age estimates for the appearance of phasmatodean-like stick insects, nearly 30 million years older than the previous putative records. The new exquisite specimen is fossilized on a slab with weak ripple-marks, suggesting the action of microbial mats favoring the preservation of its delicate structures. Further prospections in sites with this type of preservation could enrich our understanding of early evolutionary history of insects.

A tree of leaves: Phylogeny and historical biogeography of the leaf insects (Phasmatodea: Phylliidae)

The insect order Phasmatodea is known for large slender insects masquerading as twigs or bark. In contrast to these so-called stick insects, the subordinated clade of leaf insects (Phylliidae) are dorso-ventrally flattened and therefore resemble leaves in a unique way. Here we show that the origin of extant leaf insects lies in the Australasian/Pacific region with subsequent dispersal westwards to mainland Asia and colonisation of most Southeast Asian landmasses. We further hypothesise that the clade originated in the Early Eocene after the emergence of angiosperm-dominated rainforests. The genus Phyllium to which most of the ~100 described species pertain is recovered as paraphyletic and its three non-nominate subgenera are recovered as distinct, monophyletic groups and are consequently elevated to genus rank. This first phylogeny covering all major phylliid groups provides the basis for future studies on their taxonomy and a framework to unveil more of their cryptic and underestimated diversity.

Integrative Taxonomy of the Spinous Assassin Bug Genus Sclomina (Heteroptera: Reduviidae: Harpactorinae) Reveals Three Cryptic Species Based on DNA Barcoding and Morphological Evidence

Simple Summary

The assassin bugs (Heteroptera: Reduviidae) are one of the largest and morphologically most diverse families of true bug, having essential impacts on forest ecosystems as predators. The spinous reduviid genus Sclomina exhibits shape mimicry and protective coloration adapted to the spinous Rubus plant that they inhabit. The genus Sclomina shows gradual morphological variability, so its morphological classification is still unresolved, and its biology is almost unknown. In this study, DNA barcodes and morphological evidence were combined to accurately divide the species of a comprehensive collection sampled in South China and North Vietnam. We found three cryptic species. The biological information and mimicry behavior uncover their successive evolutionary survival strategies.

Abstract

Sclomina Stål, 1861 (Heteroptera: Reduviidae: Harpactorinae) is endemic to China and Vietnam, with only two species, Sclomina erinacea Stål, 1861 and Sclomina guangxiensis Ren, 2001, characterized by spinous body and dentate abdominal connexivum. However, due to variable morphological characteristics, Sclomina erinacea, which is widely distributed in South China, is possibly a complex of cryptic species, and Sclomina guangxiensis was suspected to be an extreme group of the S. erinacea cline. In the present study, we conducted species delimitation and phylogenetic analyses based on the mitochondrial cytochrome c oxidase subunit I (COI) gene sequences of 307 Sclomina specimens collected from 30 sampling localities combined with morphological evidence. The result showed that all samples used in this study were identified as five species: Sclomina guangxiensis is a valid species, and Sclomina erinacea actually includes three cryptic species: Sclomina xingrensis P. Zhao and Cai sp. nov., Sclomina pallens P. Zhao and Cai sp. nov., and Sclomina parva P. Zhao and Cai sp. nov. In this paper, the genus Sclomina is systematically revised, and the morphological characteristics of the five species are compared, described, and photographed in detail. We elucidate the evolutionary history of Sclomina based on results of estimated divergence time. The body shape and coloration (green in nymph and brown in adult) of Sclomina match their environment and mimic the Rubus plants on which they live. The symbiotic relationship between Sclomina and spinous Rubus plants is presented and discussed.

Moss mimesis par excellence: integrating previous and new data on the life history and larval ecomorphology of long-bodied craneflies (Diptera: Cylindrotomidae: Cylindrotominae)

Different physical structures play a central role in animal camouflage. However, in evolutionary studies of mimicry, the ecological and evolutionary significance of such structures has been poorly investigated. Larvae of long-bodied craneflies, Cylindrotominae, are all obligate herbivores and resemble plants. They are distinctively characterized by possessing numerous elongated cuticular lobes on the integument. A comprehensive overview of the biology and morphology of cylindrotomids, particularly their larval stages, is laid out, providing original data on nine species. To explore the ecological background of moss resemblance, host-plants of most examined species are clarified, revealing that terrestrial moss-feeding species tend to use specific groups of mosses, either belonging to Bryales or Hypnales. However, the evolution of cryptic forms remains paradoxical, due to the apparent absence of visual predators. Based on histological examinations, extensive internal musculatures within the cuticular lobes on the lateral side are discovered, shedding new light on their function in locomotion. Traditional functional explanations for these lobes, particularly as devices for respiration, locomotion and attachment, are challenged. This study promotes our understanding of the ecomorphology of mimicry devices, which is an angle often dismissed in evolutionary studies of mimicry.

Genetic Mapping of Climbing and Mimicry: Two Behavioral Traits Degraded During Silkworm Domestication

Behavioral changes caused by domestication in animals are an important issue in evolutionary biology. The silkworm, Bombyx mori, is an ideal fully domesticated insect model for studying both convergent domestication and behavior evolution. We explored the genetic basis of climbing for foraging and mimicry, two degraded behaviors during silkworm domestication, in combination of bulked segregant analysis (BSA) and selection sweep screening. One candidate gene, ASNA1, located in the 3-5 Mb on chromosome 19, harboring a specific non-synonymous mutation in domestic silkworm, might be involved in climbing ability. This mutation was under positive selection in Lepidoptera, strongly suggesting its potential function in silkworm domestication. Nine candidate domesticated genes related to mimicry were identified on chromosomes 13, 21, and 27. Most of the candidate domesticated genes were generally expressed at higher levels in the brain of the wild silkworm. This study provides valuable information for deciphering the molecular basis of behavioral changes associated with silkworm domestication.

Integrated phylogenomic and fossil evidence of stick and leaf insects (Phasmatodea) reveal a Permian-Triassic co-origination with insectivores

Stick and leaf insects (Phasmatodea) are a distinctive insect order whose members are characterized by mimicking various plant tissues such as twigs, foliage and bark. Unfortunately, the phylogenetic relationships among phasmatodean subfamilies and the timescale of their evolution remain uncertain. Recent molecular clock analyses have suggested a Cretaceous-Palaeogene origin of crown Phasmatodea and a subsequent Cenozoic radiation, contrasting with fossil evidence. Here, we analysed transcriptomic data from a broad diversity of phasmatodeans and, combined with the assembly of a new suite of fossil calibrations, we elucidate the evolutionary history of stick and leaf insects. Our results differ from recent studies in the position of the leaf insects (Phylliinae), which are recovered as sister to a clade comprising Clitumninae, Lancerocercata, Lonchodinae, Necrosciinae and Xenophasmina. We recover a Permian to Triassic origin of crown Phasmatodea coinciding with the radiation of early insectivorous parareptiles, amphibians and synapsids. Aschiphasmatinae and Neophasmatodea diverged in the Jurassic-Early Cretaceous. A second spur in origination occurred in the Late Cretaceous, coinciding with the Cretaceous Terrestrial Revolution, and was probably driven by visual predators such as stem birds (Enantiornithes) and the radiation of angiosperms.

Lichen mimesis in mid-Mesozoic lacewings

Animals mimicking other organisms or using camouflage to deceive predators are vital survival strategies. Modern and fossil insects can simulate diverse objects. Lichens are an ancient symbiosis between a fungus and an alga or a cyanobacterium that sometimes have a plant-like appearance and occasionally are mimicked by modern animals. Nevertheless, lichen models are almost absent in fossil record of mimicry. Here, we provide the earliest fossil evidence of a mimetic relationship between the moth lacewing mimic Lichenipolystoechotes gen. nov. and its co-occurring fossil lichen model Daohugouthallus ciliiferus. We corroborate the lichen affinity of D. ciliiferus and document this mimetic relationship by providing structural similarities and detailed measurements of the mimic's wing and correspondingly the model's thallus. Our discovery of lichen mimesis predates modern lichen-insect associations by 165 million years, indicating that during the mid-Mesozoic, the lichen-insect mimesis system was well established and provided lacewings with highly honed survival strategies.

3-D imaging reveals four extraordinary cases of convergent evolution of acoustic communication in crickets and allies (Insecta)

When the same complex trait is exhibited by closely related species, a single evolutionary origin is frequently invoked. The complex stridulatory apparatus present in the forewings of extant crickets, mole crickets, katydids, and prophalangopsids, is currently interpreted as sharing a single common origin due to their similarity and unique function. An alternative hypothesis of convergent evolution in these ensiferan groups has challenged this common view, but remained controversial because of competing interpretations of wing venation. Here we propose another hypothesis for the widely and long debated homology of ensiferan stridulatory apparatus, performing the first 3D reconstruction of hidden structures at the wing bases. This approach allowed defining the homology of each vein from its very origin rather than after its more distal characteristics, which may be subjected to environmental pressure of selection. The stridulatory apparatus involves different veins in these four singing clades. In light of the most recent phylogenetic evidence, this apparatus developed four times in Ensifera, illustrating extraordinary convergent evolutions between closely related clades, by far exceeding the number of evolutionary steps ever proposed for calling ability in this group.