Maternal Care under Large Clutches with Small Eggs: The Evolution of Life History Traits in Shield Bugs.

AbstractPatterns in the correlated evolution of parental care and life history traits are long established but controversial. Although parental care is related to large egg size in many taxa, conflicting results have also been reported. To test the evolutionary relationships between parental care and life history traits, we performed phylogenetic comparative analyses using shield bugs (Heteroptera: Acanthosomatidae), in which maternal guarding of eggs and young has repeatedly evolved. Our analyses revealed that female body size affected reproductive resource allocation. Contrary to the expectations of current theories, the acquisition of maternal care was associated with small eggs, large clutches, and large egg resource allocation. There was a greater trade-off between egg size and clutch size in caring species than in noncaring species. Egg and hatchling developmental rates were not correlated with egg size but were slower in caring species than in noncaring species. Analyses of evolutionary transitions suggest that the establishment of large clutches, small eggs, and large egg resource allocation preceded the evolution of maternal care. To our knowledge, this is the first study clarifying the evolution of parental care linked with small eggs in invertebrates.

Are males just passive? Coupling mechanism of the Brazilian cave insects with inverted genitalia.

Species of the Brazilian cave barklouse genus Neotrogla (Psocodea: "Psocoptera": Trogiomorpha: Prionoglarididae: Sensitibillini) are known to have a "female penis (gynosome)" that functions as an intromittent organ inserted into the membranous pouches in the simple male genital chamber during copulation to receive semen. However, the functions of other male and female genital structures and the copulatory processes of Neotrogla were completely unknown to date. Based on µCT observation of the male and female postabdomen and connected muscles both before and in copula, we clarified the functions of the male and female genital structures. In addition, based on the analyses of the established 3D models, we concluded that precise and rigid contact of multiple genital structures, and step-by-step releases of each holding mechanism achieved by the cooperation of both sexes are involved in the copulatory processes. The coevolution between the male and female genital structures in Neotrogla may provide a new example for the evolution of tolerance traits.

Phylogenomics of Parasitic and Nonparasitic Lice (Insecta: Psocodea): Combining Sequence Data and Exploring Compositional Bias Solutions in Next Generation Data Sets.

The insect order Psocodea is a diverse lineage comprising both parasitic (Phthiraptera) and nonparasitic members (Psocoptera). The extreme age and ecological diversity of the group may be associated with major genomic changes, such as base compositional biases expected to affect phylogenetic inference. Divergent morphology between parasitic and nonparasitic members has also obscured the origins of parasitism within the order. We conducted a phylogenomic analysis on the order Psocodea utilizing both transcriptome and genome sequencing to obtain a data set of 2370 orthologous genes. All phylogenomic analyses, including both concatenated and coalescent methods suggest a single origin of parasitism within the order Psocodea, resolving conflicting results from previous studies. This phylogeny allows us to propose a stable ordinal level classification scheme that retains significant taxonomic names present in historical scientific literature and reflects the evolution of the group as a whole. A dating analysis, with internal nodes calibrated by fossil evidence, suggests an origin of parasitism that predates the K-Pg boundary. Nucleotide compositional biases are detected in third and first codon positions and result in the anomalous placement of the Amphientometae as sister to Psocomorpha when all nucleotide sites are analyzed. Likelihood-mapping and quartet sampling methods demonstrate that base compositional biases can also have an effect on quartet-based methods.[Illumina; Phthiraptera; Psocoptera; quartet sampling; recoding methods.].

Why Did a Female Penis Evolve in a Small Group of Cave Insects?

The evolution of a female penis is an extremely rare event and is only known to have occurred in a tribe of small cave insects, Sensitibillini (Psocodea: Trogiomorpha: Prionoglarididae). The female penis, which is protrudable and inserted into the male vagina-like cavity during copulation to receive semen, is thought to have evolved independently twice in this tribe, in the Brazilian Neotrogla and the African Afrotrogla. These findings strongly suggest that there are some factors unique to Sensitibillini that have facilitated female penis evolution. Here, several hypothetical factors are presented that may have enabled the evolution of the female penis in Sensitibillini. The female-female competition for nutritious semen, the oligotrophic environment, and the twin insemination slots with switching valve are considered to be the driving factors for female penis evolution. Additionally, the following factors are considered responsible for relaxing the constraint against female penis evolution: preexistence of the female-above mating position, the elongated duct connecting the female pre-penis with the sperm storage organ, and the small male genital cavity accepting the female genital tubercle bearing the opening of this duct. Understanding the factors enabling female penis evolution may also shed light on the evolution of the male penis.

Phylogenomics and the evolution of hemipteroid insects.

Hemipteroid insects (Paraneoptera), with over 10% of all known insect diversity, are a major component of terrestrial and aquatic ecosystems. Previous phylogenetic analyses have not consistently resolved the relationships among major hemipteroid lineages. We provide maximum likelihood-based phylogenomic analyses of a taxonomically comprehensive dataset comprising sequences of 2,395 single-copy, protein-coding genes for 193 samples of hemipteroid insects and outgroups. These analyses yield a well-supported phylogeny for hemipteroid insects. Monophyly of each of the three hemipteroid orders (Psocodea, Thysanoptera, and Hemiptera) is strongly supported, as are most relationships among suborders and families. Thysanoptera (thrips) is strongly supported as sister to Hemiptera. However, as in a recent large-scale analysis sampling all insect orders, trees from our data matrices support Psocodea (bark lice and parasitic lice) as the sister group to the holometabolous insects (those with complete metamorphosis). In contrast, four-cluster likelihood mapping of these data does not support this result. A molecular dating analysis using 23 fossil calibration points suggests hemipteroid insects began diversifying before the Carboniferous, over 365 million years ago. We also explore implications for understanding the timing of diversification, the evolution of morphological traits, and the evolution of mitochondrial genome organization. These results provide a phylogenetic framework for future studies of the group.

Mitochondrial phylogenomics and genome rearrangements in the barklice (Insecta: Psocodea).

The mitochondrial genome arrangement in the insect order Psocodea (booklice, barklice, and parasitic lice) is extremely variable. Genome organization ranges from the rearrangement of a few tRNAs and protein coding genes, through extensive tRNA and protein coding gene rearrangements, to subdivision into multiple mini-chromosomes. Evolution of the extremely modified mitochondrial genome in parasitic lice (Phthiraptera) has been the subject of several studies, but limited information is available regarding the mitochondrial genome organization of the more plesiomorphic, free-living Psocodea (formerly known as the "Psocoptera"). In particular, the ancestral state of the psocodean mitochondrial genome arrangement and the evolutionary pathway to the rearranged conditions are still unknown. In this study, we addressed mitochondrial evolutionary questions within the Psocodea by using mitochondrial genome sequences obtained from a wide range of Psocoptera, covering all three suborders. We identified seven types of mitochondrial genome arrangements in Psocoptera, including the first example in Psocodea of retention of the ancestral pancrustacean condition in Prionoglaris (Prionoglarididae). Two methods (condition-based parsimony reconstruction and common-interval genome distances) were applied to estimate the ancestral mitochondrial arrangement in Psocodea, and both provided concordant results. Specifically, the common ancestor of Psocodea retained the ancestral pancrustacean condition, and most of the gene arrangement types have originated independently from this ancestral condition. We also utilized the genomic data for phylogenetic estimation. The tree estimated from the mitochondrial genomic data was well resolved, strongly supported, and in agreement with previously estimated phylogenies. It also provided the first robust support for the family Prionoglarididae, as its monophyly was uncertain in previous morphological and molecular studies.

Independent origins of female penis and its coevolution with male vagina in cave insects (Psocodea: Prionoglarididae).

The cave-dwelling psocid tribe Sensitibillini (Afrotrogla, Neotrogla and Sensitibilla) is of special morphological and evolutionary interest because of its possession of reversed copulatory organs: i.e. females of Afrotrogla and Neotrogla have a penis-like organ. The female penis structure is highly variable among taxa, as is the case of the male penis in animals with normal copulatory organs. Here, we present the first molecular phylogeny of Sensitibillini and analyse the evolutionary pattern of their genitalia. Afrotrogla and Neotrogla did not form a monophyletic clade, and their female penis structures are significantly different, suggesting two independent origins of the female penis within Sensitibillini. In Neotrogla, the species that has a simple female penis is embedded among species that have an elaborate penis, and detailed structures of the female penis elaborations are in exact agreement among species, suggesting a secondary simplification of the female penis. A correlated evolutionary pattern between male and female genitalia was also detected. This coevolution of genitalia may suggest that sexual conflict or cryptic 'male' choice drove the diversity of the female penis, as is the case of male penile diversity in animals with conventional genitalia.

Molecular phylogeny reveals genital convergences and reversals in the barklouse genus Trichadenotecnum (Insecta: Psocodea: 'Psocoptera': Psocidae).

Trichadenotecnum is one of the most diverse genera among the non-parasitic members of Psocodea (Insecta: "Psocoptera"). The genus shows a world-wide distribution (excluding the Australian Region, where only one introduced species is known) with its center of diversity in southern to eastern Asia. Several species groups had been proposed for this large genus based on morphology, but their validity and phylogenetic relationships are still unclear because of great morphological diversity in the genitalia, systematically the most relevant character. In this study, we estimated the molecular phylogeny of the Old World species of Trichadenotecnum based on extensive taxon sampling. As a result, the monophyly of morphology-based species groups was very strongly supported in most cases. However, two groups were recovered as non-monophyletic, which had been inadequately defined on the basis of plesiomorphies or convergences of genital characters. First, the monophyly of the sexpunctatum group was not supported because the medium group was found to be embedded within this group. The simpler genitalia observed in the medium group were considered to be derived from the more complicated genitalia present in the sexpunctatum group. Second, the monophyly of the majus group was not supported for two reasons: (1) It was divided into two distant clades which initially had been united on the basis of convergent similarities of the male genitalia. (2) Two species groups were revealed to be embedded within the main clade of the majus group; the initial separation of these groups had been based on reversals to the ancestral genital condition.

Maternal care in Acanthosomatinae (Insecta: Heteroptera: Acanthosomatidae)--correlated evolution with morphological change.

BACKGROUND: Maternal care (egg-nymph guarding behavior) has been recorded in some genera of Acanthosomatidae. However, the origin of the maternal care in the family has remained unclear due to the lack of phylogenetic hypotheses. Another reproductive mode is found in non-caring species whose females smear their eggs before leaving them. They possess pairs of complex organs on the abdominal venter called Pendergrast's organ (PO) and spread the secretion of this organ onto each egg with their hind legs, which is supposed to provide a protective function against enemies. Some authors claim that the absence of PO may be associated with the presence of maternal care. No study, however, has tested this hypothesis of a correlated evolution between the two traits. RESULTS: We reconstructed the molecular phylogeny of the subfamily Acanthosomatinae using five genetic markers sequenced from 44 species and one subspecies with and without maternal care. Eight additional species from the other two acanthosomatid subfamilies were included as outgroups. Our results indicated that maternal care has evolved independently at least three times within Acanthosomatinae and once in the outgroup species. Statistical tests for correlated evolution showed that the presence of maternal care is significantly correlated with the secondary loss or reduction of PO. Ancestral state reconstruction for the node of Acanthosoma denticaudum (a non-caring species in which egg smearing with developed POs occurs) and A. firmatum (a caring species with reduced POs) suggested egg smearing was still present in their most recent common ancestor and that maternal care in A. firmatum has evolved relatively recently. CONCLUSIONS: We showed that maternal care is an apomorphic trait that has arisen multiple times from the presence of PO within the subfamily Acanthosomatinae. The acquisition of maternal care is correlated with the reduction or loss of PO, which suggests an evolutionary trade-off between the two traits resulting from physiological costs. This prediction also implies that presence of maternal care can be highly expected for those groups lacking behavioral data, which invariably also lack the organ. No secondary loss of maternal care was detected in the present tree. We suggest that the loss of maternal care may be suppressed due to the vulnerability of the PO-free condition, which thus maintains maternal care.

Evolution of attachment structures in the highly diverse Acercaria (Hexapoda).

Acercaria display an unusually broad array of adhesive devices occurring on different parts of the legs. Attachment structures of all major subgroups are described and illustrated. Nineteen characters of the distal leg region were combined with a data matrix containing 99 additional morphological characters of different body parts. The results of the cladistic analysis are largely congruent with current hypotheses. Zoraptera are not retrieved as close relatives of Acercaria. The monophyly of the entire lineage and of the major subgroups Psocodea, Phthiraptera, and Hemiptera is confirmed. Our data also support the monophyly of Auchenorrhycha and a sister-group relationship between Thysanoptera and Hemiptera (Condylognatha). In contrast to other lineages of insects, the hairy type of adhesive device is present only in one group within the Acercaria (Heteroptera, Cimicomorpha). The arolium is present in the groundplan but missing in several groups (e.g. Psocodea, Cicadoidea, Aphidoidea). Pretarsal pulvilli evolved several times independently. Tarsal euplantulae and different specialized clasping devices have evolved within Phthiraptera, whereas pretarsal attachment devices are missing in this ectoparasitic group. The potential to modify pretarsal attachment devices in their structural details has probably contributed to the very successful diversification of the predominantly phytophagous Hemiptera.

Comparisons of host specificity in feather louse genera (Insecta: Phthiraptera: Philopteridae) parasitizing gulls (Aves: Laridae: Larus).

Data from gene sequences and morphological structures were collected for the gull feather lice, Saemundssonia lari, Quadraceps punctatus, and Q. ornatus, parasitizing Larus crassirostris and L. schistisagus. Saemundssonia lari was collected from both gull species, and no detectable morphological and genetic differences were found between lice collected from the two different hosts. In contrast, Q. punctatus was only collected from L. crassirostris, whereas Q. ornatus was only collected from L. schistisagus. The two Quadraceps species were genetically highly divergent, and body-size differences corresponding to the gull's body size (Harrison's rule) were also detected between them. Both Quadraceps species were collected from the interbarb of the remex or rectrix, and a match in body size between the louse and the interbarb space may be important in escape from host preening defenses. In contrast, Saemundssonia is a head louse, inhabiting the finer feathers of the head and neck, which the bird cannot preen. A close match to host body size may be less important for lice in the head microhabitat. The differences in the pattern of host-specificity between Saemundssonia and Quadraceps on the two focal host species of this study were probably due to their different microhabitat preferences. More broadly, comparisons of the gene sequences of S. lari and Q. punctatus to those from other gull hosts showed that genetically almost undifferentiated populations of both species were distributed on wide range of gull species. Frequent interspecific hybridization of gulls is one possible factor that may allow these lice to maintain gene flow across multiple host species.

Two new species of Cameraria Chapman (Lepidoptera: Gracillariidae) associated with Salix or Cornus in Japan.

Two new species of the genus Cameraria Chapman, 1902, Cameraria riparia sp. nov. and Cameraria corni sp. nov., are described from Japan. Larval setal maps, illustrations and/or photographs of wing patterns, wing venations and genitalia are provided for both species, and the systematic positions of the two species are discussed based on their morphologies. The larvae of C. riparia feed on Salix spp. and make blotch mines, whereas C. corni larvae feed on Cornus kousa subsp. kousa and make linear blotch mines. C. riparia was collected on Hokkaido and Honshu Islands, and considerable differences in the male genital characters were detected between the two populations. However, a molecular phylogenetic analysis based on the COI barcode region indicated that there was no clear genetic differentiation between the two populations (maximum divergence, 1.41%). C. corni was collected on Honshu and Kyushu Islands, and this is the first record of the trophic association of Lithocolletinae with Cornaceae.

Morphology of the pterothoracic musculature in Paraneoptera and its phylogenetic implication (Insecta: Neoptera).

Although the monophyly of Paraneoptera (=hemipteroid orders or Acercaria, composed of Psocodea, Thysanoptera and Hemiptera) has been widely accepted morphologically, the results from molecular phylogenetic and phylogenomic analyses contradict this hypothesis. In particular, phylogenomic analyses provide strong bootstrap support for the sister group relationship between Psocodea and Holometabola, that is, paraphyly of Paraneoptera. Here, we examined the pterothoracic musculature of Paraneoptera, as well as a wide range of other neopterous insect orders, and analysed its phylogenetic implication. By using the synchrotron microcomputed tomography (µCT) and parsimony-based ancestral state reconstruction, several apomorphic conditions suggesting the monophyly of Paraneoptera, such as the absence of the II/IIItpm7, IIscm3, IIIspm2 and IIIscm3 muscles, were identified. In contrast, no characters supporting Psocodea + Holometabola were recovered from the thoracic muscles. These results provide additional support for the monophyly of Paraneoptera, together with the previously detected morphological apomorphies of the head, wing base, and abdomen.

Parallel evolution of novelties: extremely long intromittent organs in the leaf beetle subfamily Criocerinae.

Extreme elongation of a part of the intromittent organ, the flagellum, has occurred several times in Criocerinae (Chrysomelidae). These leaf beetles have acquired a specialized pocket to store the flagellum in the abdominal cavity, at the same time allowing a quick control of movements of this structure during copulation. We investigated the morphogenesis of the intromittent organs of species with and without a flagellum to discuss the evolutionary background of parallel evolution of novel structures. We found that the specialized pocket is formed by the invagination of an epidermal layer and a resultant rotation of the primary gonopore. Invagination itself is a well-known phenomenon in morphogenetic processes, which leads us to hypothesize that the novelty is formed by co-opting a previously acquired genetic system. A large open-space is present within the intromittent organ during the entire morphogenesis in species without a flagellum, and the invagination in the species with a flagellum grows in the corresponding area. This means that there are no physical impediments for the growth of a large pocket. In addition the sites of muscular attachments in the species with a flagellum are also different from those without it. The differentiation of muscles is completed immediately before adult emergence, which means the muscles are adjustable during the entire morphogenesis in this group. Simple modifications probably based on a co-option of previously acquired genetic systems, the potential space for adding a new element, and an adjustable factor in morphogenesis of the intromittent organ facilitate the parallel evolution of the extreme elongation.

Changes in base composition bias of nuclear and mitochondrial genes in lice (Insecta: Psocodea).

While it is well known that changes in the general processes of molecular evolution have occurred on a variety of timescales, the mechanisms underlying these changes are less well understood. Parasitic lice ("Phthiraptera") and their close relatives (infraorder Nanopsocetae of the insect order Psocodea) are a group of insects well known for their unusual features of molecular evolution. We examined changes in base composition across parasitic lice and bark lice. We identified substantial differences in percent GC content between the clade comprising parasitic lice plus closely related bark lice (=Nanopsocetae) versus all other bark lice. These changes occurred for both nuclear and mitochondrial protein coding and ribosomal RNA genes, often in the same direction. To evaluate whether correlations in base composition change also occurred within lineages, we used phylogenetically controlled comparisons, and in this case few significant correlations were identified. Examining more constrained sites (first/second codon positions and rRNA) revealed that, in comparison to the other bark lice, the GC content of parasitic lice and close relatives tended towards 50 % either up from less than 50 % GC or down from greater than 50 % GC. In contrast, less constrained sites (third codon positions) in both nuclear and mitochondrial genes showed less of a consistent change of base composition in parasitic lice and very close relatives. We conclude that relaxed selection on this group of insects is a potential explanation of the change in base composition for both mitochondrial and nuclear genes, which could lead to nucleotide frequencies closer to random expectation (i.e., 50 % GC) in the absence of any mutation bias. Evidence suggests this relaxed selection arose once in the non-parasitic common ancestor of Phthiraptera + Nanopsocetae and is not directly related to the evolution of the parasitism in lice.

Atrichadenotecnum multispinosus sp. n. (Psocoptera: Psocidae) from southwestern China, with new synonyms and new combinations from Psocomesites and Clematostigma.

Atrichadenotecnum multispinosus sp. n. is described from southwestern China. Psocomesites and Clematostigma from China are discussed, with five species transferred to Atrichadenotecnum and four species placed as new synonyms. Keys to adult males and females of Atrichadenotecnum species are presented.

Zorotypus in Peninsular Malaysia (Zoraptera: Zorotypidae), with the description of three new species.

Three new species of the uncommonly encountered insect order Zoraptera are described and figured from Peninsular Malaysia--Zorotypus magnicaudelli sp. n., Zorotypus cervicornis sp. n., and Zorotypus impolitus sp. n. Another species from the region, identified as Zorotypus caudelli Karny, 1927, was also collected and is reevaluated herein based on new material. A brief discussion of characters used in zorapteran systematics is provided, and a key to the species of Peninsular Malaysia provided. This is the first report for the order Zoraptera from Peninsular Malaysia.

Acquisition of novel muscles enabled protruding and retracting mechanisms of female penis in sex-role reversed cave insects.

Brazilian sex-role reversed cave insects (genus Neotrogla) have a striking structure called the gynosome (or female penis), which deeply penetrates male vagina-like genitalia during copulation to receive nutritious semen. However, the protruding and retracting mechanisms of the female penis, including their evolutionary origin, are poorly understood. By using micro-computed tomography (µCT), we compared the genital morphology and musculature between species with a gynosome and others lacking this structure. As a result, we discovered two groups of muscles related to the protrusion and retraction of gynosomes. These muscles were also observed in species with non-protrusible prepenis. This suggests that evolution of these muscles preceded the acquisition of the protruding function of the gynosome, originally having a putative stimulatory function to receive nutritious semen. This intermediate stage probably allowed for the reversal of genital functions.

Co-phylogeography and morphological evolution of sika deer lice (Damalinia sika) with their hosts (Cervus nippon).

Lice are obligate parasites of mammals and birds and have become an important model for studies of host-parasite co-evolution and co-phylogenetics. Population genetic and phylogeographic studies represent an important bridge between microevolution and co-phylogenetic patterns. We examine co-phylogeographic patterns in sika deer and their parasitic lice. Co-phylogeographic patterns in deer and lice were evaluated using homologous regions of mitochondrial COI sequences. The phylogeographic breaks recovered for deer populations matched those of previous studies. Comparisons of the phylogeographic tree topology for deer lice with that of their hosts revealed a significant level of congruence. However, comparisons of genetic distances between deer and lice suggested that one of the estimated co-divergence events is more likely a recent host switch. Taking into account genetic divergence, there is not strong evidence for complete phylogeographic co-divergence between deer and their parasitic lice. However, mitochondrial phylogenies only track genetic structure of female lineages, and the incongruence between deer and louse phylogeography may be explained by louse migration mediated by male deer. Morphological analysis of head shape variation based on an elliptic Fourier descriptor showed that overall morphological variation contained phylogenetic signal, suggesting that in general morphology of these lice evolves congruent to population history.

Exploration of the homology among the muscles associated with the female genitalia of the three suborders of Psocodea (Insecta).

By using µCT technology, we reconstructed 3D models of the female genital structures and associated muscles of seven species from three suborders of Psocodea (free-living species only, formerly known as independent insect order "Psocoptera"). The homology of the female genital structures and associated muscles of different species is discussed. A total of 21 muscle groups were observed, and except for one muscle, all were homologized throughout the order. Moreover, some of the homologous muscles could be identified confidently in holometabolan insects. Using the muscles as landmarks, we discuss the homology of the ovipositor valves between Psocodea and other neopteran insects. Most importantly, the ovipositor of the suborder Trogiomorpha was identified to consist of the well-developed external valve (V3) plus a remnant of the dorsal valve (V2). We also examined the phylogenetic information included in the female genital muscles and found that certain muscles provide useful information and support deeper nodes (e.g., monophyly of the suborder Psocomorpha). The present study of female genital muscles not only helps us to better understand the phylogeny of Psocodea but also provides a solid foundation for research on muscle evolution.