Extreme convergence in stick insect evolution: phylogenetic placement of the Lord Howe Island tree lobster

Genome skimming for improved phylogenetics of Taiwanese phasmids (Insecta: Phasmatodea)

Taiwan, a relatively young continental island, harbors a high proportion of endemic phasmids, reflecting its unique evolutionary history. However, a comprehensive phylogenetic framework to clarify these phasmids is still lacking. In this study, we sequenced ten of eleven valid genera and two undescribed species of Taiwanese phasmids (total 16 species) using the genome-skimming approach. We also integrated these sequences with public databases to create two aligned datasets: one comprising 92 taxa (mitogenomes) and the other 606 taxa (seven nuclear and mitochondrial genes), enabling us to examine their phylogenetic relationships using longer sequences and more samples. Our analyses show that Taiwanese phasmids should be categorized into six families, with a revised number of genera to 13. Furthermore, four species require taxonomic treatments: namely Micadina honei (Günther, 1940) comb. nov., Micadina truncatum (Shiraki, 1935) comb. nov., Otraleus okunii (Shiraki, 1935) comb. nov., and Ramulus granulatus (Shiraki, 1935) syn. nov. now recognized as Ramulus artemis (Westwood, 1859). While some Taiwanese genera exhibit polyphyletic relationships, our findings highlight the importance of taxon sampling, particularly for type species in resolving these systematic issues. The genome-skimming approach has proven to be an excellent method for producing comparable sequence datasets, facilitating the investigation of highly diverse insects, even when samples are old, small, or have highly fragmented DNAs.

Purging of Highly Deleterious Mutations Through an Extreme Bottleneck

Transitions to captivity often produce population bottlenecks. On the one hand, bottlenecks increase inbreeding and decrease effective population size, thus increasing extinction risk. On the other hand, elevated homozygosity associated with inbreeding may purge deleterious mutations. Previous empirical studies of purging in captive breeding programs have focused on phenotypic measurements. We test natural selection's ability to purge deleterious mutations following an extreme population bottleneck by analyzing patterns of genetic diversity in wild and captive-bred individuals of the Lord Howe Island stick insect, Dryococelus australis. Dryococelus australis has been bred in captivity for two decades, having passed through an extreme bottleneck-only two mating pairs with few new additions since then. The magnitude of the bottleneck together with high female fecundity but low offspring recruitment set up nearly ideal conditions for the purging of deleterious mutations. As expected, captive-bred individuals had a greater number of long runs of homozygosity compared with wild individuals, implying strong inbreeding in captivity which would facilitate purging in homozygous regions. Stop-codon mutations were preferentially depleted in captivity compared with other mutations in coding and noncoding regions. The more deleterious a mutation was predicted to be, the more likely it was found outside of runs of homozygosity, implying that inbreeding facilitates the expression and thus removal of deleterious mutations, even after such an extreme bottleneck and under the benign conditions of captivity. These data implicate inbreeding and recessive deleterious mutation load in fitness variation among captive and wild D. australis.

A review of Sadyattes Stål, 1875, with the descriptions of six new species from the Philippines (Phasmatodea: Platycraninae: Stephanacridini)

The genus Sadyattes Stål, 1875 is a poorly understood clade of stick insects of the subfamily Platycraninae and tribe Stephanacridini, that currently comprises three species from Borneo as well as type-species S. borrii Stål, 1875 whose locality is as yet a mystery. In its present recognition the genus is here shown to be paraphyletic and research has revealed that a number of species currently attributed to other genera, one of which is not even closely related, actually belong in Sadyattes. To elucidate these shortcomings a taxonomic review of Sadyattes at the species level is presented along with a generic redescription. Sadyattes is distributed throughout the land masses of the Sunda Shelf (Borneo, Peninsular Malaysia, Java and Sumatra with some of its surrounding islands) and the Philippine Islands. Differential diagnoses as well as notes on intraspecific variability and the distributions are provided for all known species, including new descriptions and combinations, with most species also illustrated. Keys are presented to distinguish females and males. The genus Eucarcharus Brunner v. Wattenwyl, 1907 is found to be a synonym of Sadyattes and thus synonymised (syn. nov.). The two Philippine species previously contained in Eucarcharus, E. fallax Brunner v. Wattenwyl, 1907 and E. feruloides (Westwood, 1859), are automatically transferred to Sadyattes, which results in two new generic combinations (comb. nov.). Four species are transferred to Sadyattes from other genera, which results in another four new generic combinations (comb. nov.): the Bornean S. decoris (Seow-Choen, 2016) and S. incertus (Brunner v. Wattenwyl, 1907) from Peninsular Malaysia, Bangka Island and the Andaman Islands from the genus Phobaeticus Brunner v. Wattenwyl, 1907 (Clitumninae: Pharnaciini), the Bornean S. nigricornis (Redtenbacher, 1908) from the genus Pharnacia Stål, 1877 (Clitumninae: Pharnaciini), and the Philippine S. leytensis (Zompro, 1997) from the genus Hermarchus Stål, 1875 (Platycraninae: Stephanacridini). Six new species from the Philippines are described: S. banwaon sp. nov. from the island of Mindanao from the female, S. maganda sp. nov. from the island of Mindoro from the female and male, S. matipuno sp. nov. from the island of Luzon from the female, male and egg, S. mindanaense sp. nov. from the island of Mindanao from the female, male and egg, S. panayense sp. nov. from the island of Panay from the female only, and S. tubaense sp. nov. from the island of Luzon from the male. A redescription of the male of the type-species S. borrii Stål, 1875 is presented, whose distribution is here shown to comprise Java and Sumatra, along with a description of the previously unrecorded female, which has proven to be represented by Nesiophasma zanus Hennemann, 1998 (syn. nov.). This latter synonymy renders the questionable locality "New Guinea" of Nesiophasma zanus as erroneous. The previously unknown males of S. feruloides comb. nov., S. fallax comb. nov., and S. incertus comb. nov. are described and those of the latter two species are illustrated for the first time. Also, the eggs of S. fallax comb. nov. and S. feruloides comb. nov. are described and illustrated for the first time. Nearchus grubaueri Redtenbacher, 1908 is re-synonymised with S. incertus (Brunner v. Wattenwyl, 1907; rev. syn.). Holotypes of the newly described species are deposited in the collections of Institute Royal des Sciences Naturelles de Belgique, Brussels, Belgium (RBINS) and the Natural History Museum, London, U.K. (NHMUK).

Divergence time and environmental similarity predict the strength of morphological convergence in stick and leaf insects

Independent evolution of similar traits in lineages inhabiting similar environments (convergent or repeated evolution) is often taken as evidence for adaptation by natural selection, and used to illustrate the predictability of evolution. Yet convergence is rarely perfect for two reasons. First, environments may not be as similar as they appear. Second, responses to selection are contingent upon available genetic variation and independent lineages may differ in the alleles, genetic backgrounds, and even the developmental mechanisms responsible for the phenotypes in question. Both impediments to convergence are predicted to increase as the length of time separating two lineages increases, making it difficult to discern their relative importance. We quantified environmental similarity and the extent of convergence to show how habitat and divergence time each contribute to observed patterns of morphological evolution in 212 species of stick and leaf insects (order Phasmatodea). Dozens of phasmid lineages independently colonized similar habitats, repeatedly evolving in parallel directions on a 23-trait morphospace, though the magnitude and direction of these shifts varied. Lineages converging toward more similar environments ended up closer on the morphospace, as did closely related lineages, and closely related lineages followed more parallel evolutionary trajectories to arrive there than more distantly related ones. Remarkably, after accounting for habitat similarity, we show that divergence time reduced the extent of convergence at a constant rate across more than 100 My of separation, suggesting even the magnitude of contingency can be predictable, given sufficient spans of time.

Insight into the Phylogenetic Relationships of Phasmatodea and Selection Pressure Analysis of Phraortes liaoningensis Chen & He, 1991 (Phasmatodea: Lonchodidae) Using Mitogenomes

Stick and leaf insects are a group among the Insecta that are famous for their extraordinary mimicry ability. Since the establishment of the Phasmatodea, their internal classification has been constantly revised. Mitochondrial genes as molecular markers have been widely used for species classification, but the phylogenetic relationships within the Phasmatodea remain to be thoroughly discussed. In the present study, five mitogenomes of Phasmatodea ranging from 15,746 bp to 16,747 bp in length were sequenced. Bayesian inference (BI) and maximum likelihood (ML) analyses were carried out based on a 13 PCGs data matrix (nt123) and a combined matrix of 13 PCGs and two rRNA genes (nt123_rRNA). The present study supports the conclusion that Phylliidae was the basal group of Neophasmatodea and confirms the monophyly of Lonchodinae and Necrosciinae, but it shows that Lonchodidae was polyphyletic. A sister group of Bacillidae and Pseudophasmatidae was also recovered. The phylogenetic tree based on the nt_123 dataset showed higher node support values. The construction of a divergent time tree in this study supported the conclusion that extant Phasmatodea originated in the Jurassic (170 Mya) and most lineages diverged after the Cretaceous-Paleogene extinction event. To explore whether the mitochondrial genes of Phraortes liaoningensis collected from high latitudes where low temperatures occur for eight months of the year are under selection pressure, this study used the branch-site model and the branch model to analyze the selection pressure on the 13 mitochondria protein-coding genes (PCGs). We found that both ND2 and ND4L of Ph. liaoningensis exhibited positive selection sites using the branch-site model. This study shows that a low-temperature environment causes mitochondrial genes to be selected to meet the energy requirements for survival.

Studies on Neotropical Phasmatodea XXVI: Taxonomic review of Cladomorformia tax. n., a lineage of Diapheromerinae stick insects, with the descriptions of seven new genera and 41 new species (Phasmatodea: Occidophasmata: Diapheromerinae)

Stick and leaf insects (Phasmatodea) are a moderately diverse order that comprises almost 3,500 extant species of large to very large often impressively camouflaged nocturnal herbivores. The order also stands out as one of the few insect orders that have until lately lacked a robust higher-level phylogeny and still the relationships between many New World taxa in particular remain unknown. The Diapheromerinae is one of the main lineages of the Occidophasmata and comprises a bulk of the diversity of New World stick insects. The clade is endemic to the Americas and includes the longest insects of that region. During the past 25 years Diapheromerinae has experienced various often inconsistent attempts of a classification, which have resulted in a complicated history that has meanwhile constituted a heterogenous mixture of historical and contemporary views. To counter these challenges workers have made use of rank-free taxa to provisionally group supposedly monophyletic clades. Currently the Diapheromerinae are sub-divided into the two tribes Diapheromerini and Oreophoetini and recent molecular analyses have shown taxa of the Cladomorphinae Günther, 1953 to belong to Diapheromerinae. Certainly, the clade still deserves much work to delimit meaningful sub-groups within Diapheromerinae reflective of their evolutionary history and the results of the latest comprehensive molecular-based phylogenetic studies already imply sub-divisions within the Diapheromerini. The rank-free taxon Cladomorformia tax. n. is established to comprise former Cladomorphini, Cranidiini, Otocrania Redtenbacher, 1908 as well as sections of Diapheromerini sensu Robertson et al., 2018, which are the genera that have previously been placed in the "Phanocles group" sensu Zompro, 2001 as well as two genera of the "Bacteria group" and one genus of the "Clonistria group": Alienobostra, Bostriana, Calynda, Globocalynda, Laciphorus, Phanocles, Phanocloidea and Trychopeplus. The genus Cranidium and all genera of Cladomorphini sensu Hennemann et al., 2016 are here formally transferred to Diapheromerinae, this is Aplopocranidium, Cladomorphus, Jeremia, Jeremiodes, Otocraniella and Xylodus. A holistic review of Cladomorformia at the genus level is conducted herein and new diagnoses, differentiations and keys to all 25 genera that are now contained in that clade are presented. Lists of species are provided for all genera, which include detailed type data, synonymies and distributional records. Moreover, identification keys to all 163 known valid species are provided to render identification of species within the 25 known genera possible. In total, 232 species are covered if the 69 synonymous taxa are included. The subfamily Haplopodinae is introduced to comprise all genera of the tribes Haplopodini, Hesperophasmatini and Pterinoxylini as classified by Hennemann et al. (2016) as well as the recently described Teruelphasmini. Renaming former Cladomorphinae sensu Robertson et al. (2018) into Haplopodinae is necessary, because the type-genus Cladomorphus can no longer be considered a member of that lineage and belongs in Diapheromerinae. Haplopodinae is the only New World clade that belongs into the Old World Oriophasmata. Bostranova Villet, 2023 has been introduced to replace the preoccupied Bostra Stål, 1875. The type-species of Bostranova, Bacteria turgida Westwood, 1859, however is here shown to belong in Phanocloidea Zompro, 2001. Thus, Bostranova is synonymised under Phanocloidea (n. syn.) and all species are transferred to Phanocloidea and other genera. Paraphanocles Zompro, 2001 (Type-species: Mantis keratosqueleton Olivier, 1792) is synonymised with Phanocles Stål, 1875 (syn. n.). Seven new genera are described: Globocrania gen. n. (Type-species: Bacteria emesa Westwood, 1859), Hirtuleiodes gen. n. (Type-species: Phibalosoma gibbosa Chopard, 1911), Lanceobostra gen. n. (Type-species: Bacteria aetolus Westwood, 1859), Ocreatophasma gen. n. (Type-species: Ocreatophasma elegans sp. n.), Parotocrania gen. n. (Type-species: Parotocrania panamae sp. n.), Phanoclocrania gen. n. (Type-species: Bostra dorsuaria Stål, 1875) and Spinocloidea gen. n. (Type-species: Spinocloidea panamaense sp. n.). All seven genera are described from both sexes and the eggs, with the exception of Ocreatophasma gen. n., which is known from the females only. Forty-one new species are described: Globocalynda cornuta sp. n. from Ecuador, Globocalynda marcapatae sp. n. from Peru, Globocalynda ruficollis sp. n. from Bolivia, Hirtuleiodes peruanus sp. n. from Peru, Jeremiodes costaricensis sp. n. from Costa Rica, Jeremiodes ecuadoricus sp. n. from Ecuador, Jeremiodes peruanus sp. n. from Peru, Lanceobostra chapalaense sp. n. from Mexico, Lanceobostra glabra sp. n. from Mexico, Lanceobostra oaxacaee sp. n. from Mexico, Lanceobostra ornata sp. n. from Mexico, Lanceobostra torquata sp. n. from Mexico, Lanceobostra tuckerae sp. n. from Mexico, Ocreatophasma elegans gen. n., sp. n. from Peru, Ocreatophasma fragile gen. n., sp. n. from Peru, Ocreatophasma modestum gen. n., sp. n. from Peru, Parotocrania acutilobata gen. n., sp. n. from Ecuador, Parotocrania curvata gen. n., sp. n. from Peru, Parotocrania panamae gen. n., sp. n. from Panama, Phanocles acutecornutus sp. n. from Ecuador, Phanocles barbadosense sp. n. from Barbados, Phanocles berezini sp. n. from Mexico, Phanocles brevipes sp. n. from Peru, Phanocles chiapasense sp. n. from Mexico, Phanocles cuzcoense sp. n. from Peru, Phanocles ecuadoricus sp. n. from Ecuador, Phanocles falcatus sp. n. from Ecuador, Phanocles maximus sp. n. from Panama, Phanocles mexicanus sp. n. from Mexico, Phanocles pleurospinosus sp. n. from Costa Rica, Phanocles rehni sp. n. from Honduras, Phanocles solidus sp. n. from Ecuador, Phanocles spectabilis sp. n. from Costa Rica, Phanocles superbus sp. n. from Ecuador, Phanocloidea sanguinea sp. n. from Ecuador, Phanocloidea semiptera sp. n. from Venezuela, Phanocloidea venezuelica sp. n. from Venezuela, Spinocloidea panamaense gen. n., sp. n. from Panama, Spinocloidea splendida gen. n., sp. n. from Colombia and Spinocloidea tumescens gen. n., sp. n. from Costa Rica. With a maximum recorded body length of 285.0 mm the new species Phanocles maximus sp. n. from Panama is the longest extant insect of the Americas and the Occidophasmata clade. A total of 132 taxonomic changes are conducted: 64 species are transferred to other genera and 43 new synonyms are established. Lectotypes are designated for 25 taxa to ensure stability of the concerned names or new synonymies here established. Moreover, the previously unknown females of five and males of twelve species are described and illustrated for the first time. Colour illustrations are presented of the eggs of 39 species, of which those of 26 species are formally described and illustrated for the first time.

Descriptions of two new stick insect species of Cnipsomorpha Hennemann, Conle, Zhang & Liu (Phasmatodea) from China based on integrative taxonomy

Accurate taxonomical identification is an extremely important basis for stick insect research, including evolutionary biology but also applied biology such as pest control. In addition, genetic methods are a valuable identification auxiliary technology at present. Therefore, this paper used morphological and molecular data to investigate five stick insect specimens from the genus Cnipsomorpha in Yunnan, successfully identifying two new species: Cnipsomorphayunnanensis Xu, Jiang & Yang, sp. nov. and C.yuxiensis Xu, Jiang & Yang, sp. nov. A phylogenetic tree was constructed through their 28S and COI genes in order to infer the phylogenetic position of the two new species. Photographs of the new species and a key to all known Cnipsomorpha species are provided.

Nine Mitochondrial Genomes of Phasmatodea with Two Novel Mitochondrial Gene Rearrangements and Phylogeny

The classification of stick and leaf insects (Order Phasmatodea) is flawed at various taxonomic ranks due to a lack of robust phylogenetic relationships and convergent morphological characteristics. In this study, we sequenced nine new mitogenomes that ranged from 15,011 bp to 17,761 bp in length. In the mitogenome of Carausis sp., we found a translocation of trnR and trnA, which can be explained by the tandem duplication/random loss (TDRL) model. In the Stheneboea repudiosa Brunner von Wattenwyl, 1907, a novel mitochondrial structure of 12S rRNA-CR1-trnI-CR2-trnQ-trnM was found for the first time in Phasmatodea. Due to the low homology of CR1 and CR2, we hypothesized that trnI was inverted through recombination and then translocated into the middle of the control region. Control region repeats were frequently detected in the newly sequenced mitogenomes. To explore phylogenetic relationships in Phasmatodea, mtPCGs from 56 Phasmatodean species (composed of 9 stick insects from this study, 31 GenBank data, and 16 data derived from transcriptome splicing) were used for Bayesian inference (BI), and maximum likelihood (ML) analyses. Both analyses supported the monophyly of Lonchodinae and Necrosciinae, but Lonchodidae was polyphyletic. Phasmatidae was monophyletic, and Clitumninae was paraphyletic. Phyllidae was located at the base of Neophasmatodea and formed a sister group with the remaining Neophasmatodea. Bacillidae and Pseudophasmatidae were recovered as a sister group. Heteroptergidae was monophyletic, and the Heteropteryginae sister to the clade (Obriminae + Dataminae) was supported by BI analysis and ML analysis.

Leaves that walk and eggs that stick: comparative functional morphology and evolution of the adhesive system of leaf insect eggs (Phasmatodea: Phylliidae)

Phylliidae are herbivorous insects exhibiting impressive cryptic masquerade and are colloquially called "walking leaves". They imitate angiosperm leaves and their eggs often resemble plant seeds structurally and in some cases functionally. Despite overall morphological similarity of adult Phylliidae, their eggs reveal a significant diversity in overall shape and exochorionic surface features. Previous studies have shown that the eggs of most Phylliidae possess a specialised attachment mechanism with hierarchical exochorionic fan-like structures (pinnae), which are mantled by a film of an adhesive secretion (glue). The folded pinnae and glue respond to water contact, with the fibrous pinnae expanding and the glue being capable of reversible liquefaction. In general, the eggs of phylliids appear to exhibit varying structures that were suggested to represent specific adaptations to the different environments the eggs are deposited in. Here, we investigated the diversity of phylliid eggs and the functional morphology of their exochorionic structure. Based on the examination of all phylliid taxa for which the eggs are known, we were able to characterise eleven different morphological types. We explored the adhesiveness of these different egg morphotypes and experimentally compared the attachment performance on a broad range of substrates with different surface roughness, surface chemistry and tested whether the adhesion is replicable after detachment in multiple cycles. Furthermore, we used molecular phylogenetic methods to reconstruct the evolutionary history of different egg types and their adhesive systems within this lineage, based on 53 phylliid taxa. Our results suggest that the egg morphology is congruent with the phylogenetic relationships within Phylliidae. The morphological differences are likely caused by adaptations to the specific environmental requirements for the particular clades, as the egg morphology has an influence on the performance regarding the surface roughness. Furthermore, we show that different pinnae and the adhesive glue evolved convergently in different species. While the evolution of the Phylliidae in general appears to be non-adaptive judging on the strong similarity of the adults and nymphs of most species, the eggs represent a stage with complex and rather diverse functional adaptations including mechanisms for both fixation and dispersal of the eggs.

Three new genera and one new species of leaf insect from Melanesia (Phasmatodea, Phylliidae)

With the first large-scale Phylliidae molecular phylogeny recently published adding a great deal of clarity to phylliid diversity, several of the rarer species which could not be included were methodically and morphologically reviewed. This review resulted in identification of numerous substantial morphological features that suggest there are Melanesian clades that create polyphyletic groups within the phylliids which should instead be taxonomically recognized as unique. These rarer Melanesia species have historically been considered to be southern representatives of the Pulchriphyllium Griffini, 1898 sensu lato. However, there are notable morphological differences between the Pulchriphyllium sensu stricto and the "schultzei" group. Therefore, two new genera are erected, Vaabonbonphyllium gen. nov. from the Solomon Islands and Papua New Guinea and Rakaphyllium gen. nov. from New Guinea and the Aru Islands. Erection of these two new genera warrants the following new combinations: Rakaphylliumschultzei (Giglio-Tos, 1912), comb. nov., Rakaphylliumexsectum (Zompro, 2001b), comb. nov., and Vaabonbonphylliumgroesseri (Zompro, 1998), comb. nov. Additionally, while reviewing material an undescribed Vaabonbonphyllium gen. nov. specimen was located and is herein described as Vaabonbonphylliumrafidahae gen. et sp. nov. from Mt. Hagen, Papua New Guinea. Additionally, a morphologically unique clade of several species recovered as sister to the Nanophyllium sensu stricto was recognized and their numerous unique morphological features and monophyly leads the authors to erect the new genus Acentetaphyllium gen. nov. which warrants the following new combinations: Acentetaphylliumbrevipenne (Größer, 1992), comb. nov., Acentetaphylliumlarssoni (Cumming, 2017), comb. nov., Acentetaphylliummiyashitai (Cumming et al. 2020), comb. nov., and Acentetaphylliumstellae (Cumming, 2016), comb. nov. With the addition of several new genera, a key to phylliid genera is included for adult males and females.

Macroevolutionary Analyses Provide New Evidence of Phasmid Wings Evolution as a Reversible Process

The concept that complex ancestral traits can never be recovered after their loss is still widely accepted, despite phylogenetic and molecular approaches suggest instances where phenotypes may have been lost throughout the evolutionary history of a clade and subsequently reverted back in derived lineages. One of the first and most notable examples of such a process is wing evolution in phasmids; this polyneopteran order of insects, which comprises stick and leaf insects, has played a central role in initiating a long-standing debate on the topic. In this study, a novel and comprehensive time tree including over 300 Phasmatodea species is used as a framework for investigating wing evolutionary patterns in the clade. Despite accounting for several possible biases and sources of uncertainty, macroevolutionary analyses consistently revealed multiple reversals to winged states taking place after their loss, and reversibility is coupled with higher species diversification rates. Our findings support a loss of or reduction in wings that occurred in the lineage leading to the extant phasmid most recent common ancestor, and brachyptery is inferred to be an unstable state unless co-opted for nonaerodynamic adaptations. We also explored how different assumptions of wing reversals probability could impact their inference: we found that until reversals are assumed to be over 30 times more unlikely than losses, they are consistently inferred despite uncertainty in tree and model parameters. Our findings demonstrate that wing evolution is a reversible and dynamic process in phasmids and contribute to our understanding of complex trait evolution.

A second view on the evolution of flight in stick and leaf insects (Phasmatodea)

BACKGROUND

The re-evolution of complex characters is generally considered impossible, yet, studies of recent years have provided several examples of phenotypic reversals shown to violate Dollo's law. Along these lines, the regain of wings in stick and leaf insects (Phasmatodea) was hypothesised to have occurred several times independently after an ancestral loss, a scenario controversially discussed among evolutionary biologists due to overestimation of the potential for trait reacquisition as well as to the lack of taxonomic data.

RESULTS

We revisited the recovery of wings by reconstructing a phylogeny based on a comprehensive taxon sample of over 500 representative phasmatodean species to infer the evolutionary history of wings. We additionally explored the presence of ocelli, the photoreceptive organs used for flight stabilisation in winged insects, which might provide further information for interpreting flight evolution. Our findings support an ancestral loss of wings and that the ancestors of most major lineages were wingless. While the evolution of ocelli was estimated to be dependent on the presence of (fully-developed) wings, ocelli are nevertheless absent in the majority of all examined winged species and only appear in the members of few subordinate clades, albeit winged and volant taxa are found in every euphasmatodean lineage.

CONCLUSION

In this study, we explored the evolutionary history of wings in Phasmatodea and demonstrate that the disjunct distribution of ocelli substantiates the hypothesis on their regain and thus on trait reacquisition in general. Evidence from the fossil record as well as future studies focussing on the underlying genetic mechanisms are needed to validate our findings and to further assess the evolutionary process of phenotypic reversals.

How to approach the study of syndromes in macroevolution and ecology

Syndromes, wherein multiple traits evolve convergently in response to a shared selective driver, form a central concept in ecology and evolution. Recent work has questioned the existence of some classic syndromes, such as pollination and seed dispersal syndromes. Here, we discuss some of the major issues that have afflicted research into syndromes in macroevolution and ecology. First, correlated evolution of traits and hypothesized selective drivers is often relied on as the only evidence for adaptation of those traits to those hypothesized drivers, without supporting evidence. Second, the selective driver is often inferred from a combination of traits without explicit testing. Third, researchers often measure traits that are easy for humans to observe rather than measuring traits that are suited to testing the hypothesis of adaptation. Finally, species are often chosen for study because of their striking phenotypes, which leads to the illusion of syndromes and divergence. We argue that these issues can be avoided by combining studies of trait variation across entire clades or communities with explicit tests of adaptive hypotheses and that taking this approach will lead to a better understanding of syndrome-like evolution and its drivers.

Three Complete Mitochondrial Genomes of Orestes guangxiensis, Peruphasma schultei, and Phryganistria guangxiensis (Insecta: Phasmatodea) and Their Phylogeny

Insects of the order Phasmatodea are mainly distributed in the tropics and subtropics and are best known for their remarkable camouflage as plants. In this study, we sequenced three complete mitochondrial genomes from three different families: Orestes guangxiensis, Peruphasma schultei, and Phryganistria guangxiensis. The lengths of the three mitochondrial genomes were 15,896 bp, 16,869 bp, and 17,005 bp, respectively, and the gene composition and structure of the three stick insects were identical to those of the most recent common ancestor of insects. The phylogenetic relationships among stick insects have been chaotic for a long time. In order to discuss the intra- and inter-ordinal relationship of Phasmatodea, we used the 13 protein-coding genes (PCGs) of 85 species for maximum likelihood (ML) and Bayesian inference (BI) analyses. Results showed that the internal topological structure of Phasmatodea had a few differences in both ML and BI trees and long-branch attraction (LBA) appeared between Embioptera and Zoraptera, which led to a non-monophyletic Phasmatodea. Consequently, after removal of the Embioptera and Zoraptera species, we re-performed ML and BI analyses with the remaining 81 species, which showed identical topology except for the position of Tectarchus ovobessus (Phasmatodea). We recovered the monophyly of Phasmatodea and the sister-group relationship between Phasmatodea and Mantophasmatodea. Our analyses also recovered the monophyly of Heteropterygidae and the paraphyly of Diapheromeridae, Phasmatidae, Lonchodidae, Lonchodinae, and Clitumninae. In this study, Peruphasma schultei (Pseudophasmatidae), Phraortes sp. YW-2014 (Lonchodidae), and species of Diapheromeridae clustered into the clade of Phasmatidae. Within Heteropterygidae, O. guangxiensis was the sister clade to O. mouhotii belonging to Dataminae, and the relationship of (Heteropteryginae + (Dataminae + Obriminae)) was recovered.

Resolving a century-old case of generic mistaken identity: polyphyly of Chitoniscus sensu lato resolved with the description of the endemic New Caledonia Trolicaphyllium gen. nov. (Phasmatodea, Phylliidae)

With every molecular review involving Chitoniscus Stål, 1875 sensu lato samples from Fiji and New Caledonia revealing polyphyly, the morphology from these two distinct clades was extensively reviewed. Morphological results agree with all previously published molecular studies and therefore Trolicaphylliumgen. nov. is erected to accommodate the former Chitoniscus sensu lato species restricted to New Caledonia, leaving the type species Chitoniscuslobiventris (Blanchard, 1853) and all other Fijian species within Chitoniscus sensu stricto. Erection of this new genus for the New Caledonian species warrants the following new combinations: Trolicaphylliumbrachysoma (Sharp, 1898), comb. nov., Trolicaphylliumerosus (Redtenbachher, 1906), comb. nov., and Trolicaphylliumsarrameaense (Größer, 2008a), comb. nov. Morphological details of the female, male, freshly hatched nymph, and egg are illustrated and discussed alongside the Chitoniscus sensu stricto in order to differentiate these two clades which have been mistaken as one for decades.

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.

Physical constraints lead to parallel evolution of micro- and nanostructures of animal adhesive pads: a review

Adhesive pads are functional systems with specific micro- and nanostructures which evolved as a response to specific environmental conditions and therefore exhibit convergent traits. The functional constraints that shape systems for the attachment to a surface are general requirements. Different strategies to solve similar problems often follow similar physical principles, hence, the morphology of attachment devices is affected by physical constraints. This resulted in two main types of attachment devices in animals: hairy and smooth. They differ in morphology and ultrastructure but achieve mechanical adaptation to substrates with different roughness and maximise the actual contact area with them. Species-specific environmental surface conditions resulted in different solutions for the specific ecological surroundings of different animals. As the conditions are similar in discrete environments unrelated to the group of animals, the micro- and nanostructural adaptations of the attachment systems of different animal groups reveal similar mechanisms. Consequently, similar attachment organs evolved in a convergent manner and different attachment solutions can occur within closely related lineages. In this review, we present a summary of the literature on structural and functional principles of attachment pads with a special focus on insects, describe micro- and nanostructures, surface patterns, origin of different pads and their evolution, discuss the material properties (elasticity, viscoelasticity, adhesion, friction) and basic physical forces contributing to adhesion, show the influence of different factors, such as substrate roughness and pad stiffness, on contact forces, and review the chemical composition of pad fluids, which is an important component of an adhesive function. Attachment systems are omnipresent in animals. We show parallel evolution of attachment structures on micro- and nanoscales at different phylogenetic levels, focus on insects as the largest animal group on earth, and subsequently zoom into the attachment pads of the stick and leaf insects (Phasmatodea) to explore convergent evolution of attachment pads at even smaller scales. Since convergent events might be potentially interesting for engineers as a kind of optimal solution by nature, the biomimetic implications of the discussed results are briefly presented.

Evolutionary morphology of the antennal heart in stick and leaf insects (Phasmatodea) and webspinners (Embioptera) (Insecta: Eukinolabia)

The morphology of the antennal hearts in the head of Phasmatodea and Embioptera was investigated with particular reference to phylogenetically relevant key taxa. The antennal circulatory organs of all examined species have the same basic construction: they consist of antennal vessels that are connected to ampullae located in the head near the antenna base. The ampullae are pulsatile due to associated muscles, but the points of attachment differ between the species studied. All examined Phasmatodea species have a Musculus (M.) interampullaris which extends between the two ampullae plus a M. ampulloaorticus that runs from the ampullae to the anterior end of the aorta; upon contraction, all these muscles dilate the lumina of both ampullae at the same time. In Embioptera, only the australembiid Metoligotoma has an M. interampullaris. All other studied webspinners instead have a M. ampullofrontalis which extends between the ampullae and the frontal region of the head capsule; these species do not have M. ampulloaorticus. Outgroup comparison indicates that an antennal heart with a M. interampullaris is the plesiomorphic character state among Embioptera and the likely ground pattern of the taxon Eukinolabia. Antennal hearts with a M. ampullofrontalis represent a derived condition that occurs among insects only in some embiopterans. These findings help to further clarify the controversially discussed internal phylogeny of webspinners by supporting the view that Australembiidae are the sister group of the remaining Embioptera.

Evolution of adult male horn developmental phenotypes and character displacement in Xylotrupes beetles (Scarabaeidae)

Character displacement that leads to divergent phenotypes between sympatric species has been hypothesized to facilitate coexistence and promote the accumulation of biodiversity. However, there are alternative evolutionary mechanisms that may also lead to the evolution of phenotypic divergence between sympatric species; one of the mechanisms is evolutionary contingency. We studied the evolution of the presence and absence of a major male horn phenotype, which may have ecological implications for promoting coexistence between sympatric beetles, across geographic populations from different Xylotrupes beetles. By using a previously published phylogeny with 80 Xylotrupes taxa, we estimated the transition rates between the two phenotypic states (i.e., presence vs. absence of a major male phenotype). Based on the estimated transition rates, we then simulated possible phenotypic outcomes between sympatric species. We found that sympatric species were equally likely to evolve the same versus distinct phenotypic states based on the estimated transition rates given the phylogeny. The empirically observed number of sympatric species showing different phenotypic states can be explained by evolutionary contingency alone. We discussed the importance of applying phylogenetic comparative methods when studying phenotypic evolution and more generally to investigate the effect of stochastic processes before making deterministic inferences.

Do sexually selected weapons drive diversification?

Sexual selection is often thought to promote speciation. This expectation is largely driven by the fact that sexually selected traits can influence mating patterns and contribute to reproductive isolation. Indeed, some comparative studies have shown that clades with sexually selected traits have increased rates of speciation and diversification. However, these studies have almost exclusively focused on one mechanism of sexual selection: female choice. Another widespread mechanism is male-male competition. Few empirical studies (if any) have investigated the role of this alternative mechanism in driving diversification. Nevertheless, recent reviews have suggested that male-male competition can increase speciation rates. Here, we investigated whether traits associated with precopulatory male-male competition (i.e., sexually selected weapons) have promoted speciation and diversification in insects. We focused on three clades with both weapons and suitable phylogenies: leaf-footed and broad-headed bugs (Coreidae+Alydidae; ∼2850 species), stick insects and relatives (Phasmatodea; ∼3284 species), and scarab beetles (Scarabaeoidea; ∼39,717 species). We found no evidence that weapon-bearing lineages in these clades have higher rates of speciation or diversification than their weaponless relatives. Thus, our results suggest that precopulatory male-male competition may not have strong, general effects on speciation and diversification in insects, a group encompassing ∼60% of all described species.

Cladistic analysis of Paraphasma (Phasmatodea: Pseudophasmatidae) highlights the importance of the phallic organ for phasmid systematics

The internal male genitalia have been poorly investigated in Phasmatodea, remaining virtually unexplored in phylogenetic studies. Here we describe and illustrate the main phallic elements in several Neotropical stick insects, with emphasis on Paraphasma (Pseudophasmatidae), and present a phylogenetic analysis of this genus. The analysis included ten terminals in the ingroup and 18 in the outgroup, and was based on 32 characters of the phallic organ and 48 of external morphology. In order to compare these datasets in terms of phylogenetic signal and level of homoplasy, the consistency and retention indices of the cladogram were calculated separately for each of them, and partial analyses were also conducted using each dataset alone. The phylogenetic reconstruction revealed Paraphasma as polyphyletic and led us to propose a new, monotypic genus, Ecuadoriphasma gen. nov., three new combinations (Ecuadoriphasma cognatum, Paraphasma trianguliferum and Tithonophasma cancellatum) and place Oestrophora as a synonym of Paraphasma. Additionally, Olcyphides hopii and Paraphasma dentatum are synonymized with Paraphasma laterale. Both external and phallic characters were determinant for the topology obtained, and the latter were less homoplastic in the phylogenetic tree. Our results highlight the usefulness of phallic morphology for inferring phylogenetic relationships in Phasmatodea, especially among closely related genera and species.

Cryptophyllium, the hidden leaf insects - descriptions of a new leaf insect genus and thirteen species from the former celebicum species group (Phasmatodea, Phylliidae)

While the leaf insects (Phylliidae) are a well-supported group within Phasmatodea, the genus Phyllium Illiger, 1798 has repeatedly been recovered as paraphyletic. Here, the Phyllium (Phyllium) celebicum species group is reviewed and its distinctiveness from the remaining Phylliini genera and subgenera in a phylogenetic context based on morphological review and a phylogenetic analysis of three genes (nuclear gene 28S and mitochondrial genes COI and 16S) from most known and multiple undescribed species is shown. A new genus, Cryptophylliumgen. nov., is erected to partially accommodate the former members of the celebicum species group. Two species, PhylliumericoriaiHennemann et al., 2009 and Phylliumbonifacioi Lit & Eusebio, 2014 morphologically and molecularly do not fall within this clade and are therefore left within Phyllium (Phyllium). The transfer of the remaining celebicum group members from Phyllium Illiger, 1798 to this new genus creates the following new combinations; Cryptophylliumathanysus (Westwood, 1859), comb. nov.; Cryptophylliumcelebicum (de Haan, 1842), comb. nov.; Cryptophylliumchrisangi (Seow-Choen, 2017), comb. nov.; Cryptophylliumdrunganum (Yang, 1995), comb. nov.; Cryptophylliumoyae (Cumming & Le Tirant, 2020), comb. nov.; Cryptophylliumparum (Liu, 1993), comb. nov.; Cryptophylliumrarum (Liu, 1993), comb. nov.; Cryptophylliumtibetense (Liu, 1993), comb. nov.; Cryptophylliumwestwoodii (Wood-Mason, 1875), comb. nov.; Cryptophylliumyapicum (Cumming & Teemsma, 2018), comb. nov.; and Cryptophylliumyunnanense (Liu, 1993), comb. nov.

The review of specimens belonging to this clade also revealed 13 undescribed species, which are described within as: Cryptophylliumanimatumgen. et sp. nov. from Vietnam: Quang Nam Province; Cryptophylliumbankoigen. et sp. nov. from Vietnam: Quang Ngai, Thua Thien Hue, Da Nang, Gia Lai, Quang Nam, and Dak Nong Provinces; Cryptophylliumbollensigen. et sp. nov. from Vietnam: Ninh Thuan Province; Cryptophylliumdaparogen. et sp. nov. from China: Yunnan Province; Cryptophylliumechidnagen. et sp. nov. from Indonesia: Wangi-wangi Island; Cryptophylliumfaulknerigen. et sp. nov. from Vietnam: Quang Ngai and Lam Dong Provinces; Cryptophylliumicarusgen. et sp. nov. from Vietnam: Lam Dong and Dak Lak Provinces; Cryptophylliumkhmergen. et sp. nov. from Cambodia: Koh Kong and Siem Reap Provinces; Cryptophylliumlimogesigen. et sp. nov. from Vietnam: Lam Dong, Dak Lak, and Dak Nong Provinces; Cryptophylliumliyananaegen. et sp. nov. from China: Guangxi Province; Cryptophylliumnuichuaensegen. et sp. nov. from Vietnam: Ninh Thuan Province; Cryptophylliumphamigen. et sp. nov. from Vietnam: Dong Nai and Ninh Thuan Provinces; and Cryptophylliumwennaegen. et sp. nov. from China: Yunnan Province. All newly described species are morphologically described, illustrated, and molecularly compared to congenerics.

With the molecular results revealing cryptic taxa, it was found necessary for Cryptophylliumwestwoodii (Wood-Mason, 1875), comb. nov. to have a neotype specimen designated to allow accurate differentiation from congenerics. To conclude, male and female dichotomous keys to species for the Cryptophylliumgen. nov. are presented.

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.

Sexual dimorphism divergence between sister species is associated with a switch in habitat use and mating system in thorny devil stick insects

The habitat and resource use of females critically affects their pattern of distribution and consequently their monoposibility by males and the mating system of a species. Shifts in habitat use are therefore likely to be associated with changes in mating system and sexual selection acting on males' phenotypes, consequently affecting patterns of sexual dimorphism. Although sexual dimorphism is often correlated with shifts in habitat use at the macroevolutionary scale, the underlying microevolutionary processes involved are typically unclear. Here, we used the New Guinean stick insect genus Eurycantha to investigate how changes in habitat use and mating system were associated with a change in sexual dimorphism seen specifically in the thorny devil stick insects (Eurycantha calcarata and Eurycantha horrida). Male thorny devils display sexually dimorphic and enlarged hindlegs endowed with a sharp spine. Sexual size dimorphism is also very reduced in these species relative to other phasmids. Using field observations, morphological measurements and radiotelemetry, we investigated changes in mating system associated with the reduction of sexual dimorphism and tested predictions from the hypothesis that sexual selection drove the evolution of this unusual male morphology. We found that thorny devils switched from solitary roosting in the canopy during the day to communal roosting inside cavities of a few host trees, shifting the distribution of females from scattered to clumped. Male thorny devils used their large hindlegs to fight with rivals for positions on the tree close to cavities containing females, and larger males were associated with cavities containing relatively more females. In contrast, the sister species, Eurycantha insularis, displays relatively small and unarmoured males (ancestral state). Adult female E. insularis were always scattered in the canopy, and this species displayed a scramble competition mating system typical of other phasmids, where mobility, rather than fighting ability, is probably critical to males' reproductive success. Overall, our study illustrates how a drastic change in sexual dimorphism can be associated with a switch from solitary to communal roosting and from a scramble competition to a defense-based polygyny mating system.

Mitochondrial genomes of stick insects (Phasmatodea) and phylogenetic considerations

Phasmatodea represents an order of hemimetabolous insects. This group includes species with extreme forms of masquerade crypsis, whereby they imitate twigs, bark, lichen, moss, and leaves. In this study, we sequenced and annotated three mitochondrial genomes (mitogenomes) from Phasmatodea. The lengths of the novel mitogenomes range from 14,162 bp to 15,879 bp. The gene content and organization correspond to those inferred for the ancestral insect. We conducted phylogenetic analyses together with the existing mitogenomes of polyneopterans and mayflies. In most cases, the Phasmatodea was non-monophyletic, with Embioptera and Zoraptera nested inside. The mitogenome sequences from Embioptera and Zoraptera suffered from high substitution rates and displayed very long branches in phylogenetic trees. The monophyletic Phasmatodea was recovered only when the analysis employed the site-heterogeneous CAT-GTR model in PhyloBayes and used the nucleotide dataset PCG_nt. The Euphasmatodea was well established by various data types and inference methods. In addition, the clade Heteropterygidae and the subfamilies Lonchodinae and Necrosciinae were strongly supported. The Australasian clade Lanceocercata was recovered across analyses. However, the Clitumninae was non-monophyletic.

Lost lovers linked at long last: elusive female Nanophyllium mystery solved after a century of being placed in a different genus (Phasmatodea, Phylliidae)

After successful laboratory rearing of both males and females from a single clutch of eggs, the genus Nanophyllium Redtenbacher, 1906 (described only from males) and the frondosum species group within Phyllium (Pulchriphyllium) Griffini, 1898 (described only from females) are found to be the opposite sexes of the same genus. This rearing observation finally elucidates the relationship of these two small body sized leaf insect groups which, for more than a century, have never been linked before. This paper synonymizes the frondosum species group with Nanophyllium Redtenbacher, 1906 in order to create a singular and clearly defined taxonomic group. Five species are transferred from the Phyllium (Pulchriphyllium) frondosum species group and create the following new combinations: Nanophylliumasekiense (Größer, 2002), comb. nov.; Nanophylliumchitoniscoides (Größer, 1992), comb. nov.; Nanophylliumfrondosum (Redtenbacher, 1906), comb. nov.; Nanophylliumkeyicum (Karny, 1914), comb. nov.; Nanophylliumsuzukii (Größer, 2008), comb. nov. The only taxon from this species group not transferred from the frondosum species group to Nanophyllium is Phyllium (Pulchriphyllium) groesseri Zompro, 1998. Based on protibial exterior lobes, this species belongs in the schultzei species group as described in Hennemann et al. 2009 and is therefore excluded from further discussion here. The rearing of Nanophyllium also yielded the male Nanophylliumasekiense (Größer, 2002), comb. nov. thus, enabling comparison of this male to the other previously known Nanophyllium species. Two new species of nano-leaf insects are described within, Nanophylliummiyashitaisp. nov., from Morobe Province, Papua New Guinea, and Nanophylliumdaphnesp. nov., from Biak Island, Papua Province, Indonesia. With such distinct sexual dimorphism in Nanophyllium between sexes, which have only now been matched up via captive rearing, illustrated within are numerous specimens which might represent the unknown opposite sexes of the many currently known species of Nanophyllium. Due to pronounced sexual dimorphism in Nanophyllium, only future captive rearing or molecular analysis will match up the many unknown sexes. To conclude, with the description of two new Nanophyllium species, dichotomous keys to species for known males and females are presented.

Adhesion Performance in the Eggs of the Philippine Leaf Insect Phyllium Philippinicum (Phasmatodea: Phylliidae)

Leaf insects (Phasmatodea: Phylliidae) exhibit perfect crypsis imitating leaves. Although the special appearance of the eggs of the species Phyllium philippinicum, which imitate plant seeds, has received attention in different taxonomic studies, the attachment capability of the eggs remains rather anecdotical. We herein elucidate the specialized attachment mechanism of the eggs of this species and provide the first experimental approach to systematically characterize the functional properties of their adhesion by using different microscopy techniques and attachment force measurements on substrates with differing degrees of roughness and surface chemistry, as well as repetitive attachment/detachment cycles while under the influence of water contact. We found that a combination of folded exochorionic structures (pinnae) and a film of adhesive secretion contribute to attachment, which both respond to water. Adhesion is initiated by the glue, which becomes fluid through hydration, enabling adaption to the surface profile. Hierarchically structured pinnae support the spreading of the glue and reinforcement of the film. This combination aids the egg’s surface in adapting to the surface roughness, yet the attachment strength is additionally influenced by the egg’s surface chemistry, favoring hydrophilic substrates. Repetitive detachment and water-mediated adhesion can optimize the location of the egg to ensure suitable environmental conditions for embryonic development. Furthermore, this repeatable and water-controlled adhesion mechanism can stimulate further research for biomimeticists, ecologists and conservationalists.

Taxonomy, phylogeny and evolution of the bumblebee bot flies (Oestridae: Hypodermatinae: Portschinskia)

The first phylogenetic study of Portschinskia is presented based on 42 adult morphological characters scored for all 11 species, including four new species Portschinskia burmensis sp. nov., Portschinskia sichuanensis sp. nov., Portschinskia xizangensis sp. nov. and Portschinskia yunnanensis sp. nov.Portschinskia luliangensis is established as a junior synonym of Portschinskia magnifica. Monophyly of Portschinskia is strongly supported by nine non-homoplasious synapomorphies. All cladograms resolve P. yunnanensis as a basal taxon and a well-resolved Portschinskia gigas clade {P. gigas + ((Portschinskia bombiformis + (P. burmensis + (P. magnifica + P. xizangensis))) + (Portschinskia himalayana + (Portschinskia przewalskyi + P. sichuanensis)))}. The only topological difference is Portschinskia loewii and Portschinskia neugebaueri either being sister taxa or branching off successively at the base of the P. gigas clade. Three colour-pattern types are recognized, with the yellow-tailed pattern optimized as the ancestral state. Our data show that the modal colour pattern of Portschinskia species is the same as in bumblebees, and a regional correlation in species diversity and colour patterns can be detected between sympatric Portschinskia and Bombus species. As a result, we suggest that colour patterns of Portschinskia can be explained as Batesian mimicry tracking locally dominant bumblebees.

Notes on the leaf insects of the genus Phyllium of Sumatra and Java, Indonesia, including the description of two new species with purple coxae (Phasmatodea, Phylliidae)

Within the last two years, the leaf insects of the genus Phyllium of both the islands of Java and Sumatra have been reviewed extensively based on morphological observations. However, cryptic species which cannot be differentiated morphologically may be present among the various populations. Since it has frequently been demonstrated that analyses based on molecular data can bring clarity in such cases, we conducted a phylogenetic analysis based on three genes (nuclear gene 28S and mitochondrial genes COI and 16S) from the Phyllium species of these islands. The results show distinct molecular divergence for several populations and suggest the presence of two new cryptic species, morphologically inseparable from Phylliumhausleithneri Brock, 1999. From Sumatra, the population originally thought to be a range expansion for Phylliumhausleithneri, is now here described as Phylliumnisussp. nov., with the only consistent morphological difference being the color of the eggs between the two populations (dark brown in P.hausleithneri and tan in P.nisussp. nov.). Further, an additional population with purple coxae from Java was morphologically examined and found to have no consistent features to separate it morphologically from the other purple coxae species. This cryptic species from Java was however shown to be molecularly distinct from the other purple coxae populations from Sumatra and Peninsular Malaysia and is here described as Phylliumgardabagusisp. nov. In addition, Phylliumgiganteum is here officially reported from Java for the first time based on both historic and modern records of male specimens.

Complementary effect of attachment devices in stick insects (Phasmatodea)

Stick insects are well adapted in their locomotion to various surfaces and topographies of natural substrates. Single pad measurements characterised the pretarsal arolia of these insects as shear-sensitive adhesive pads and the tarsal euplantulae as load-sensitive friction pads. Different attachment microstructures on the euplantulae reveal an adaptation of smooth euplantulae to smooth surfaces and nubby eupantulae to a broader range of surface roughness. However, how different attachment pads and claws work in concert and how strong the contribution of different structures is to the overall attachment performance remains unclear. We therefore assessed combinatory effects in the attachment system of two stick insect species with different types of euplantular microstructures by analysing their usage in various posture situations and the performance on different levels of substrate roughness. For comparison, we provide attachment force data of the whole attachment system. The combination of claws, arolia and euplantulae provides mechanical interlocking on rough surfaces, adhesion and friction on smooth surfaces in different directions, and facilitates attachment on different inclines and on a broad range of surface roughness, with the least performance in the range 0.3-1.0 µm. On smooth surfaces, stick insects use arolia always, but employ euplantulae if the body weight can generate load on them (upright, wall). On structured surfaces, claws enable mechanical interlocking at roughnesses higher than 12 µm. On less-structured surfaces, the attachment strength depends on the use of pads and, corroborating earlier studies, favours smooth pads on smooth surfaces, but nubby euplantulae on micro-rough surfaces.

The earliest Timematids in Burmese amber reveal diverse tarsal pads of stick insects in the mid-Cretaceous

Many extant insects have developed pad structures, euplantulae or arolia on their tarsi to increase friction or enhance adhesion for better mobility. Many polyneopteran insects with euplantulae, for example, Grylloblattodea, Mantophasmatodea and Orthoptera, have been described from the Mesozoic. However, the origin and evolution of stick insects' euplantulae are poorly understood due to rare fossil records. Here, we report the earliest fossil records of Timematodea hitherto, Tumefactipes prolongates gen. et sp. nov. and Granosicorpes lirates gen. et sp. nov., based on three specimens from mid-Cretaceous Burmese amber. Specimens of Tumefactipes prolongates gen. et sp. nov. have extremely specialized and expanded euplantulae on their tarsomere II. These new findings are the first known and the earliest fossil records about euplantula structure within Phasmatodea, demonstrating the diversity of euplantulae in Polyneoptera during the Mesozoic. Such tarsal pads might have increased friction and helped these mid-Cretaceous stick insects to climb more firmly on various surfaces, such as broad leaves, wetted tree branches or ground. These specimens provide more morphological data for us to understand the relationships of Timematodea, Euphasmatodea, Orthoptera and Embioptera, suggesting that Timematodea might be monophyletic with Euphasmatodea rather than Embioptera and Phasmatodea should have a closer relationship with Orthoptera rather than Embioptera.

Phylogenetic divergence of island biotas: Molecular dates, extinction, and "relict" lineages

Island formation is a key driver of biological evolution, and several studies have used geological ages of islands to calibrate rates of DNA change. However, many islands are home to "relict" lineages whose divergence apparently pre-dates island age. The geologically dynamic New Zealand (NZ) archipelago sits upon the ancient, largely submerged continent Zealandia, and the origin and age of its distinctive biota have long been contentious. While some researchers have interpreted NZ's biota as equivalent to that of a post-Oligocene island, a recent review of genetic studies identified a sizeable proportion of pre-Oligocene "relict" lineages, concluding that much of the biota survived an incomplete drowning event. Here, we assemble comparable genetic divergence data sets for two recently formed South Pacific archipelagos (Lord Howe; Chatham Islands) and demonstrate similarly substantial proportions of relict lineages. Similar to the NZ biota, our island reviews provide surprisingly little evidence for major genetic divergence "pulses" associated with island emergence. The dominance of Quaternary divergence estimates in all three biotas may highlight the importance of rapid biological turnover and new arrivals in response to recent climatic and/or geological disturbance and change. We provide a schematic model to help account for discrepancies between expected versus observed divergence-date distributions for island biotas, incorporating the effects of both molecular dating error and lineage extinction. We conclude that oceanic islands can represent both evolutionary "cradles" and "museums" and that the presence of apparently archaic island lineages does not preclude dispersal origins.

Versatility of Turing patterns potentiates rapid evolution in tarsal attachment microstructures of stick and leaf insects (Phasmatodea)

In its evolution, the diverse group of stick and leaf insects (Phasmatodea) has undergone a rapid radiation. These insects evolved specialized structures to adhere to different surfaces typical for their specific ecological environments. The cuticle of their tarsal attachment pads (euplantulae) is known to possess a high diversity of attachment microstructures (AMS) which are suggested to reflect ecological specializations of different groups within phasmids. However, the origin of these microstructures and their developmental background remain largely unknown. Here, based on the detailed scanning electron microscopy study of pad surfaces, we present a theoretical approach to mathematically model an outstanding diversity of phasmid AMS using the reaction-diffusion model by Alan Turing. In general, this model explains pattern formation in nature. For the first time, we were able to identify eight principal patterns and simulate the transitions among these. In addition, intermediate transitional patterns were predicted by the model. The ease of transformation suggests a high adaptability of the microstructures that might explain the rapid evolution of pad characters. We additionally discuss the functional morphology of the different microstructures and their assumed advantages in the context of the ecological background of species.

Cretaceous winged stick insects clarify the early evolution of Phasmatodea

Wingless and shorter winged stick insects are very common today, but most known extinct stick insects had fully developed wings, leading to contentious affinities among the extinct winged and extant groups. We report herein three male winged stick insects, assigned to Pterophasmatidae fam. nov., from mid-Cretaceous Myanmar (Burmese) amber. Pterophasmatidae fam. nov. are regarded as transitional taxa from extinct winged to modern wingless and shorter winged stick insects based on their similar tegmina venation with extinct Susumanioidea and some body features the same as extant Phasmatodea. However, their symmetric phallic organs comprising two consistent phallomeres are different from those of all living groups. Phylogenetic analyses suggest that the extinct winged taxa, including the new family, are the stem groups of modern stick and leaf insects, and all of them constitute the clade of Phasmatodea. New findings indicate winged and wingless stick insects' morphologies diversified significantly during or before the mid-Cretaceous.

Consistent Associations between Body Size and Hidden Contrasting Color Signals across a Range of Insect Taxa

While there have been a number of recent advances in our understanding of the evolution of animal color patterns, much of this work has focused on color patterns that are constantly displayed. However, some animals hide functional color signals and display them only transiently through behavioral displays. These displays are widely employed as a secondary defense following detection when fleeing (flash display) or when stationary (deimatic display). Yet if displays of hidden colors are so effective in deterring predation, why have not all species evolved them? An earlier study suggested that the hidden antipredatory color signals in insects are more likely to have evolved in species with large size because either (or both) (i) large cryptic prey are more frequently detected and pursued or (ii) hidden color signals in large prey are more effective in deterring predation than in small prey. These arguments should apply universally to any prey that use hidden signals, so the association between large size and hidden contrasting color signals should be evident across diverse groups of prey. In this study, we tested this prediction in five different groups of insects. Using phylogenetically controlled analysis to elucidate the relationship between body size and color contrast between forewings and hind wings, we found evidence for the predicted size-color contrast associations in four different groups of insects, namely, Orthoptera, Phasmatidae, Mantidae, and Saturniidae, but not in Sphingidae. Collectively, our study indicates that body size plays an important role in explaining variation in the evolution of hidden contrasting color signals in insects.

Stick insect in Burmese amber reveals an early evolution of lateral lamellae in the Mesozoic

Extant stick and leaf insects commonly imitate twigs or leaves, with lateral lamellae used to enhance crypsis or achieve mimicry for protection. However, the origin and early evolution of such lateral expansions among Phasmatodea are unknown, because all known Mesozoic phasmatodeans hitherto lack preserved evidence of such structures. We report here the first Mesozoic stick insect, Elasmophasma stictum gen. et sp. nov., with well-preserved, thin, lateral lamellae on the thoracic pleura, the terga of abdominal segments I-X and the ventrolateral margins of all femora. This new species, from the mid-Cretaceous amber of northern Myanmar, has a clear, stick-like body and is assigned to Euphasmatodea. The abdominal structures of E. stictum exhibit traces of multiple expansions of the terga, suggesting that such structure might have been an early development of body expansions used to improve crypsis for stick or leaf insects when they sprawled on twigs or leaves.

Epaphroditidae sensu novo, an Endemic Caribbean Family of Morphologically Divergent Praying Mantises (Insecta, Mantodea)

Three endemic Caribbean praying mantis genera with a complex taxonomic history were recently discovered to be part of a lineage that colonized the Caribbean region during the Cretaceous period (Svenson & Rodrigues, Proc R Soc B Biol Sci 284, 2017). In all classification systems proposed up to now, the three genera, Callimantis, Epaphrodita, and Gonatista, were never considered as close relatives, a reflection of their divergent morphology. More recently, the genus Brancsikia was placed with Epaphrodita in a family based on the similarity of camouflage-related morphology. To address recent phylogenetic results that do not track current classification, we compared the morphology of the three Caribbean genera with each other and representative members of traditional or current family groups. Our morphological analysis of external and male genital characters provides strong support for the Caribbean lineage despite the divergent morphological evolution present in the three genera. We raise this Caribbean lineage to family status by employing a precedent family-group name, Epaphroditidae Brunner de Wattenwyl, 1893 sensu novo. We remove Brancsikia from our new concept of Epaphroditidae, rendering the genus incertae sedis.

Comparative phylogeography of oceanic archipelagos: Hotspots for inferences of evolutionary process

Remote island archipelagos offer superb opportunities to study the evolution of community assembly because of their relatively young and simple communities where speciation contributes to the origin and evolution of community structure. There is great potential for common phylogeographic patterns among remote archipelagos that originate through hotspot volcanism, particularly when the islands formed are spatially isolated and linearly arranged. The progression rule is characterized by a phylogeographic concordance between island age and lineage age in a species radiation. Progression is most likely to arise when a species radiation begins on an older island before the emergence of younger islands of a hotspot archipelago. In the simplest form of progression, colonization of younger islands as they emerge and offer appropriate habitat, is coincident with cladogenesis. In this paper, we review recent discoveries of the progression rule on seven hotspot archipelagos. We then discuss advantages that progression offers to the study of community assembly, and insights that community dynamics may offer toward understanding the evolution of progression. We describe results from two compelling cases of progression where the mosaic genome may offer insights into contrasting demographic histories that shed light on mechanisms of speciation and progression on remote archipelagos.

Conservation Biology: A Walking Stick's Redux on Lord Howe Island

Arguably the world's rarest insect - the Lord Howe Island 'tree lobster' - is being brought back from the brink. A recent study has confirmed the identity of this species using genomic data, which backstops its reintroduction to this World Heritage listed oceanic island.

A Cretaceous-aged Palaeotropical dispersal established an endemic lineage of Caribbean praying mantises

Recent phylogenetic advances have uncovered remarkable biogeographic histories that have challenged traditional concepts of dispersal, vicariance and diversification in the Greater Antilles. Much of this focus has centred on vertebrate lineages despite the high diversity and endemism of terrestrial arthropods, which account for 2.5 times the generic endemism of all Antillean plants and non-marine vertebrates combined. In this study, we focus on three Antillean endemic praying mantis genera, Callimantis, Epaphrodita and Gonatista, to determine their phylogenetic placement and geographical origins. Each genus is enigmatic in their relation to other praying mantises due to their morphological affinities with both Neotropical and Old World groups. We recovered the three genera as a monophyletic lineage among Old World groups, which was supported by molecular and morphological evidence. With a divergence at approximately 107 Ma, the lineage originated during the break-up of Gondwana. Ancestral range reconstruction indicates the lineage dispersed from an African + Indomalayan range to the Greater Antilles, with a subsequent extinction in the Old World. The profound ecomorphic convergence with non-Caribbean groups obscured recognition of natural relationships within the same geographical distribution. To the best of our knowledge, the lineage is one of the oldest endemic animal groups in the Greater Antilles and their morphological diversity and restricted distribution mark them as a critical taxon to conserve.

Phenotypic disparity in Iberian short-horned grasshoppers (Acrididae): the role of ecology and phylogeny

BACKGROUND

The combination of model-based comparative techniques, disparity analyses and ecomorphological correlations constitutes a powerful method to gain insight into the evolutionary mechanisms that shape morphological variation and speciation processes. In this study, we used a time-calibrated phylogeny of 70 Iberian species of short-horned grasshoppers (Acrididae) to test for patterns of morphological disparity in relation to their ecology and phylogenetic history. Specifically, we examined the role of substrate type and level of ecological specialization in driving different aspects of morphological evolution (locomotory traits, chemosensitive organs and cranial morphology) in this recent radiation.

RESULTS

We found a bimodal distribution of locomotory attributes corresponding to the two main substrate type guilds (plant vs. ground); plant-perching species tend to exhibit larger wings and thicker femora than those that remain on the ground. This suggests that life form (i.e., substrate type) is an important driving force in the evolution of morphological traits in short-horned grasshoppers, irrespective of ancestry. Substrate type and ecological specialization had no significant influence on head shape, a trait that showed a strong phylogenetic conservatism. Finally, we also found a marginal significant association between the length of antennae and the level of ecological specialization, suggesting that the development of sensory organs may be favored in specialist species.

CONCLUSIONS

Our results provide evidence that even in taxonomic groups showing limited morphological and ecological disparity, natural selection seems to play a more important role than genetic drift in driving the speciation process. Overall, this study suggests that morphostatic radiations should not necessarily be considered as "non-adaptive" and that the speciation process can bind both adaptive divergence mechanisms and neutral speciation processes related with allopatric and/or reproductive isolation.