Single origin of the Mascarene stick insects: ancient radiation on sunken islands?

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.

Phylogeographical evidence for historical long-distance dispersal in the flightless stick insect Ramulus mikado

Exploring how organisms overcome geographical barriers to dispersal is a fundamental question in biology. Passive long-distance dispersal events, although infrequent and unpredictable, have a considerable impact on species range expansions. Despite limited active dispersal capabilities, many stick insect species have vast geographical ranges, indicating that passive long-distance dispersal is vital for their distribution. A potential mode of passive dispersal in stick insects is via the egg stage within avian digestive tracts, as suggested by experimental evidence. However, detecting such events under natural conditions is challenging due to their rarity. Therefore, to indirectly assess the potential of historical avian-mediated dispersal, we examined the population genetic structure of the flightless stick insect Ramulus mikado across Japan, based on a multifaceted molecular approach [cytochrome oxidase subunit I (COI) haplotypes, nuclear simple sequence repeat markers and genome-wide single nucleotide polymorphisms]. Subsequently, we identified unique phylogeographic patterns, including the discovery of identical COI genotypes spanning considerable distances, which substantiates the notion of passive long-distance genotypic dispersal. Overall, all the molecular data revealed the low and mostly non-significant genetic differentiation among populations, with identical or very similar genotypes across distant populations. We propose that long-distance dispersal facilitated by birds is the plausible explanation for the unique phylogeographic pattern observed in this flightless stick insect.

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.

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.

The phylogenic position of aschiphasmatidae in euphasmatodea based on mitochondrial genomic evidence

The mitochondrial genome (mitogenome) has been regarded as significant source of data to better understand the phylogenetic relationships within the Euphasmatodea, but no mitogenome in Aschiphasmatoidea has been sequenced to date. In this study, two mitogenomes of Orthomeria smaragdinum and Nanhuaphasma hamicercum of Aschiphasmatidae were sequenced and annotated for the first time. The same mitochondrial gene rearrangement structure was present in the two mitogenomes sequenced, showing as the translocation of tRNA-Arg and tRNA-Asn, which conformed to the tandem duplication-random loss and could be used as a possible synapomorphy for Aschiphasmatidae. The phylogenetic results based on the maximum likelihood (ML) and bayesian inference (BI) methods both showed that Aschiphasmatidae and Neophasmatodea in Euphasmatodea are sister taxa. Although the monophyly of Oriophasmata, Occidophasmata, Diapheromeridae, Phasmatidae, Lonchodidae and Bacilloidea has not been solved, the monophyly of Neophasmatodea and Phyllioidea was well supported.

Extinct before discovered? Epactoidesgiganteus sp. nov. (Coleoptera, Scarabaeidae, Scarabaeinae), the first native dung beetle to Réunion island

We describe a new species of dung beetle, Epactoidesgiganteussp. nov., from a single female specimen allegedly collected in the 19^th century on Réunion island and recently found at the Muséum national d’Histoire naturelle, Paris. This species differs from other species of Epactoides by larger size and a set of other distinctive morphological characters. Epactoidesgiganteussp. nov. is the first native dung beetle (Scarabaeinae) of Réunion, and its discovery expands the known area of distribution of the genus Epactoides, which was hitherto believed to be endemic to Madagascar. Like other taxa from Madagascar and peripheral islands (e.g., Comoro, Seychelles, Mascarenes), E.giganteussp. nov. may have reached Réunion by over-water dispersal. Given the rapid loss of biodiversity on Réunion island and the fact that no additional specimens were re-collected over the last two centuries, it is very likely that E.giganteussp. nov. has gone extinct. However, we have unconfirmed evidence that the holotype of E.giganteussp. nov. might be a mislabeled specimen from Madagascar, which would refute the presence of native dung beetles on Réunion. We discuss both hypotheses about the specimen origin and assess the systematic position of E.giganteussp. nov. by examining most of the described species of Madagascan Epactoides. Additionally, we provide a brief overview of the dung beetle fauna of Mascarene Archipelago.

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.

Divergent Gene Expression Following Duplication of Meiotic Genes in the Stick Insect Clitarchus hookeri

Some animal groups, such as stick insects (Phasmatodea), have repeatedly evolved alternative reproductive strategies, including parthenogenesis. Genomic studies have found modification of the genes underlying meiosis exists in some of these animals. Here we examine the evolution of copy number, evolutionary rate, and gene expression in candidate meiotic genes of the New Zealand geographic parthenogenetic stick insect Clitarchus hookeri. We characterized 101 genes from a de novo transcriptome assembly from female and male gonads that have homology with meiotic genes from other arthropods. For each gene we determined copy number, the pattern of gene duplication relative to other arthropod orthologs, and the potential for meiosis-specific expression. There are five genes duplicated in C. hookeri, including one also duplicated in the stick insect Timema cristinae, that are not or are uncommonly duplicated in other arthropods. These included two sister chromatid cohesion associated genes (SA2 and SCC2), a recombination gene (HOP1), an RNA-silencing gene (AGO2) and a cell-cycle regulation gene (WEE1). Interestingly, WEE1 and SA2 are also duplicated in the cyclical parthenogenetic aphid Acyrthosiphon pisum and Daphnia duplex, respectively, indicating possible roles in the evolution of reproductive mode. Three of these genes (SA2, SCC2, and WEE1) have one copy displaying gonad-specific expression. All genes, with the exception of WEE1, have significantly different nonsynonymous/synonymous ratios between the gene duplicates, indicative of a shift in evolutionary constraints following duplication. These results suggest that stick insects may have evolved genes with novel functions in gamete production by gene duplication.

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.

Phylomitogenomics provides new perspectives on the Euphasmatodea radiation (Insecta: Phasmatodea)

Phasmatodea species diversity lies almost entirely within its suborder Euphasmatodea, which exhibits a pantropical distribution and is considered to derive from a recent and rapid evolutionary radiation. To shed light on Euphasmatodea origins and diversification, we assembled the mitogenomes of 17 species from transcriptomic sequencing data and analysed them along with 22 already available Phasmatodea mitogenomes and 33 mitogenomes representing most of the Polyneoptera lineages. Maximum Likelihood and Bayesian Inference approaches retrieved consistent topologies, both showing the widespread conflict between phylogenetic approaches and traditional systematics. We performed a divergence time analysis leveraging ten fossil specimens representative of most polyneopteran lineages: the time tree obtained supports an older radiation of the clade with respect to previous hypotheses. Euphasmatodea diversification is inferred to have started ~ 187 million years ago, suggesting that the Triassic-Jurassic mass extinction and the breakup of Pangea could have contributed to the process. We also investigated Euphasmatodea mitogenomes patterns of dN, dS and dN/dS ratio throughout our time-tree, trying to characterize the selective regime which may have shaped the clade evolution.

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.

The dynamic eggs of the Phasmatodea and their apparent convergence with plants

The egg stages of animal life cycles are underappreciated in terms of their capacity for dispersal, protection, and biotic and abiotic interactions. Some of the most intriguing egg morphologies are seen in stick and leaf insects (Phasmatodea). Phasmids are charismatic insects, particularly due to their incredible camouflage, though a lesser-known fact is that their eggs are incredibly diverse in shape and structure, reflecting varying ecological niches. Perhaps most remarkable are those eggs which appear to resemble plant seeds in both their appearance and means of dispersal, such as via water and animal vectors. Numerous hypotheses surrounding the function of these egg morphologies and their apparent convergence with seeds have been proposed; however, empirical evidence remains lacking. Here, we present an initial synthesis of available evidence surrounding the ecology and dispersal strategies of phasmid eggs and weigh up the evidence for convergent evolution between phasmid eggs and seeds. In doing so, we highlight areas where further research is needed and discuss how the ecology of phasmid eggs may interplay with other aspects of phasmid ecology, distribution, and evolution.

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.

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.

Ancient mitogenomics clarifies radiation of extinct Mascarene giant tortoises (Cylindraspis spp.)

The five extinct giant tortoises of the genus Cylindraspis belong to the most iconic species of the enigmatic fauna of the Mascarene Islands that went largely extinct after the discovery of the islands. To resolve the phylogeny and biogeography of Cylindraspis, we analysed a data set of 45 mitogenomes that includes all lineages of extant tortoises and eight near-complete sequences of all Mascarene species extracted from historic and subfossil material. Cylindraspis is an ancient lineage that diverged as early as the late Eocene. Diversification of Cylindraspis commenced in the mid-Oligocene, long before the formation of the Mascarene Islands. This rejects any notion suggesting that the group either arrived from nearby or distant continents over the course of the last millions of years or had even been translocated to the islands by humans. Instead, Cylindraspis likely originated on now submerged islands of the Réunion Hotspot and utilized these to island hop to reach the Mascarenes. The final diversification took place both before and after the arrival on the Mascarenes. With Cylindraspis a deeply divergent clade of tortoises became extinct that evolved long before the dodo or the Rodrigues solitaire, two other charismatic species of the lost Mascarene fauna.

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.

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.

Clade-age-dependent diversification under high species turnover shapes species richness disparities among tropical rainforest lineages of Bulbophyllum (Orchidaceae)

Background

Tropical rainforests (TRFs) harbour almost half of the world’s vascular plant species diversity while covering only about 6–7% of land. However, why species richness varies amongst the Earth’s major TRF regions remains poorly understood. Here we investigate the evolutionary processes shaping continental species richness disparities of the pantropical, epiphytic and mostly TRF-dwelling orchid mega-genus Bulbophyllum (c. 1948 spp. in total) using diversification analyses based on a time-calibrated molecular phylogeny (including c. 45–50% spp. each from Madagascar, Africa, Neotropics, and 8.4% from the Asia-Pacific region), coupled with ecological niche modelling (ENM) of geographic distributions under present and past (Last Glacial Maximum; LGM) conditions.

Results

Our results suggest an early-to-late Miocene scenario of ‘out-of-Asia-Pacific’ origin and progressive, dispersal-mediated diversification in Madagascar, Africa and the Neotropics, respectively. Species richness disparities amongst these four TRF lineages are best explained by a time-for-speciation (i.e. clade age) effect rather than differences in net diversification or diversity-dependent diversification due to present or past spatial-bioclimatic limits. For each well-sampled lineage (Madagascar, Africa, Neotropics), we inferred high rates of speciation and extinction over time (i.e. high species turnover), yet with the origin of most extant species falling into the Quaternary. In contrast to predictions of classical ‘glacial refuge’ theories, all four lineages experienced dramatic range expansions during the LGM.

Conclusions

As the Madagascan, African and Neotropical lineages display constant-rate evolution since their origin (early-to-mid-Miocene), Quaternary environmental change might be a less important cause of their high species turnover than intrinsic features generally conferring rapid population turnover in tropical orchids (e.g., epiphytism, specialization on pollinators and mycorrhizal fungi, wind dispersal). Nonetheless, climate-induced range fluctuations during the Quaternary could still have played an influential role in the origination and extinction of Bulbophyllum species in those three, if not in all four TRF regions.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1416-1) contains supplementary material, which is available to authorized users.

No signal of deleterious mutation accumulation in conserved gene sequences of extant asexual hexapods

Loss of sex and recombination is generally assumed to impede the effectiveness of purifying selection and to result in the accumulation of slightly deleterious mutations. Empirical evidence for this has come from several studies investigating mutational load in a small number of individual genes. However, recent whole transcriptome based studies have yielded inconsistent results, hence questioning the validity of the assumption of mutational meltdown in asexual populations. Here, we study the effectiveness of purifying selection in eight asexual hexapod lineages and their sexual relatives, as present in the 1 K Insect Transcriptome Evolution (1KITE) project, covering eight hexapod groups. We analyse the accumulation of slightly deleterious nonsynonymous and synonymous point mutations in 99 single copy orthologue protein-coding loci shared among the investigated taxa. While accumulation rates of nonsynonymous mutations differed between genes and hexapod groups, we found no effect of reproductive mode on the effectiveness of purifying selection acting at nonsynonymous and synonymous sites. Although the setup of this study does not fully rule out nondetection of subtle effects, our data does not support the established consensus of asexual lineages undergoing ‘mutational meltdown’.

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.

High diversity, high insular endemism and recent origin in the lichen genus Sticta (lichenized Ascomycota, Peltigerales) in Madagascar and the Mascarenes

Lichen biodiversity and its generative evolutionary processes are practically unknown in the MIOI (Madagascar and Indian Ocean Islands) biodiversity hotspot. We sought to test the hypothesis that lichenized fungi in this region have undergone a rapid radiation, following a single colonization event, giving rise to narrow endemics, as is characteristic of other lineages of plants. We extensively sampled specimens of the lichen genus Sticta in the Mascarene archipelago (mainly Réunion) and in Madagascar, mainly in the northern range (Amber Mt and Marojejy Mt) and produced the fungal ITS barcode sequence for 148 thalli. We further produced a four-loci data matrix for 68 of them, representing the diversity and geographical distribution of ITS haplotypes. We reconstructed the phylogenetic relationships within this group, established species boundaries with morphological context, and estimated the date of the most recent common ancestor. Our inferences resolve a robust clade comprising 31 endemic species of Sticta that arose from the diversification following a single recent (c. 11 Mya) colonization event. All but three species have a very restricted range, endemic to either the Mascarene archipelago or a single massif in Madagascar. The first genus of lichens to be studied with molecular data in this region underwent a recent radiation, exhibits micro-endemism, and thus exemplifies the biodiversity characteristics found in other taxa in Madagascar and the Mascarenes.

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.

Large-scale mitochondrial DNA analysis of native honey bee Apis mellifera populations reveals a new African subgroup private to the South West Indian Ocean islands

BACKGROUND

The South West Indian Ocean (SWIO) archipelagos and Madagascar constitute a hotspot of biodiversity with a high rate of endemism. In this area, the endemic subspecies A. m. unicolor has been described in Madagascar. It belongs to the African lineage, one of the four described evolutionary lineages in honey bees. Despite a long beekeeping tradition and several recorded European introductions, few studies have been carried out on the diversity and proportion of honey bee subspecies. In order to identify and define which evolutionary lineages and potential sub-lineages are present in the SWIO, the COI-COII intergenic region and the ND2 gene of the mtDNA were sequenced in honey bee colonies from three archipelagos. An extensive sampling (n = 1184 colonies) was done in the Mascarene (La Réunion, Mauritius, Rodrigues), Seychelles (Mahé, Praslin, La Digue) and Comoros (Grande Comore, Mohéli, Anjouan, Mayotte) archipelagos. Islands genetic diversity was compared to newly sampled populations from Madagascar, continental African and European populations.

RESULTS

African lineage haplotypes were found in all islands (except for Rodrigues). Madagascar, Comoros and Seychelles had 100% of A lineage, 95.5% in La Réunion and 56.1% in Mauritius. Among all African colonies detected in the SWIO, 98.1% (n = 633) of COI-COII haplotypes described the presence of the subspecies A. M. unicolor. Both genetic markers revealed i) a new private AI mitochondrial group shared by the SWIO archipelagos and Madagascar distant from continental populations; ii) the private African haplotypes for each island suggested diversity radiation in the archipelagos; iii) the detection of the Comoros archipelago as a possible contact area between insular and continental African populations. The exotic European C and M lineages were only detected in the Mascarene archipelago, but striking differences of proportion were observed among islands. Merely 4.6% of European colonies were found in La Réunion whereas Mauritius cumulated 44%. Here, among the 84 observed COI-COII haplotypes, 50 were newly described including 13 which were private to the SWIO archipelagos and Madagascar. Similarly, 24 of the 34 found ND2 haplotypes were novel which included six haplotypes particular to the SWIO populations.

CONCLUSION

A new African subgroup was described in the SWIO region with mitochondrial genetic evidence that A. m. unicolor is the indigenous subspecies of the archipelagos surrounding Madagascar.

Horizontal Gene Transfer of Pectinases from Bacteria Preceded the Diversification of Stick and Leaf Insects

Genes acquired by horizontal transfer are increasingly being found in animal genomes. Understanding their origin and evolution requires knowledge about the phylogenetic relationships from both source and recipient organisms. We used RNASeq data and respective assembled transcript libraries to trace the evolutionary history of polygalacturonase (pectinase) genes in stick insects (Phasmatodea). By mapping the distribution of pectinase genes on a Polyneoptera phylogeny, we identified the transfer of pectinase genes from known phasmatodean gut microbes into the genome of an early euphasmatodean ancestor that took place between 60 and 100 million years ago. This transfer preceded the rapid diversification of the suborder, enabling symbiont-free pectinase production that would increase the insects’ digestive efficiency and reduce dependence on microbes. Bacteria-to-insect gene transfer was thought to be uncommon, however the increasing availability of large-scale genomic data may change this prevailing notion.

Ancestral gene duplication enabled the evolution of multifunctional cellulases in stick insects (Phasmatodea)

The Phasmatodea (stick insects) have multiple, endogenous, highly expressed copies of glycoside hydrolase family 9 (GH9) genes. The purpose for retaining so many was unknown. We cloned and expressed the enzymes in transfected insect cell lines, and tested the individual proteins against different plant cell wall component poly- and oligosaccharides. Nearly all isolated enzymes were active against carboxymethylcellulose, however most could also degrade glucomannan, and some also either xylan or xyloglucan. The latter two enzyme groups were each monophyletic, suggesting the evolution of these novel substrate specificities in an early ancestor of the order. Such enzymes are highly unusual for Metazoa, for which no xyloglucanases had been reported. Phasmatodea gut extracts could degrade multiple plant cell wall components fully into sugar monomers, suggesting that enzymatic breakdown of plant cell walls by the entire Phasmatodea digestome may contribute to the Phasmatodea nutritional budget. The duplication and neofunctionalization of GH9s in the ancestral Phasmatodea may have enabled them to specialize as folivores and diverge from their omnivorous ancestors. The structural changes enabling these unprecedented activities in the cellulases require further study.

The thorax of the cave cricket Troglophilus neglectus: anatomical adaptations in an ancient wingless insect lineage (Orthoptera: Rhaphidophoridae)

BACKGROUND

Secondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive' group of Ensifera, for which no apomorphic character has been reported so far.

RESULTS

We present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages.

CONCLUSIONS

Based on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.