Climate-land-use interactions shape tropical mountain biodiversity and ecosystem functions.

Agriculture and the exploitation of natural resources have transformed tropical mountain ecosystems across the world, and the consequences of these transformations for biodiversity and ecosystem functioning are largely unknown1-3. Conclusions that are derived from studies in non-mountainous areas are not suitable for predicting the effects of land-use changes on tropical mountains because the climatic environment rapidly changes with elevation, which may mitigate or amplify the effects of land use4,5. It is of key importance to understand how the interplay of climate and land use constrains biodiversity and ecosystem functions to determine the consequences of global change for mountain ecosystems. Here we show that the interacting effects of climate and land use reshape elevational trends in biodiversity and ecosystem functions on Africa's largest mountain, Mount Kilimanjaro (Tanzania). We find that increasing land-use intensity causes larger losses of plant and animal species richness in the arid lowlands than in humid submontane and montane zones. Increases in land-use intensity are associated with significant changes in the composition of plant, animal and microorganism communities; stronger modifications of plant and animal communities occur in arid and humid ecosystems, respectively. Temperature, precipitation and land use jointly modulate soil properties, nutrient turnover, greenhouse gas emissions, plant biomass and productivity, as well as animal interactions. Our data suggest that the response of ecosystem functions to land-use intensity depends strongly on climate; more-severe changes in ecosystem functioning occur in the arid lowlands and the cold montane zone. Interactions between climate and land use explained-on average-54% of the variation in species richness, species composition and ecosystem functions, whereas only 30% of variation was related to single drivers. Our study reveals that climate can modulate the effects of land use on biodiversity and ecosystem functioning, and points to a lowered resistance of ecosystems in climatically challenging environments to ongoing land-use changes in tropical mountainous regions.

The Chalcidoidea bush of life: evolutionary history of a massive radiation of minute wasps.

Chalcidoidea are mostly parasitoid wasps that include as many as 500 000 estimated species. Capturing phylogenetic signal from such a massive radiation can be daunting. Chalcidoidea is an excellent example of a hyperdiverse group that has remained recalcitrant to phylogenetic resolution. We combined 1007 exons obtained with Anchored Hybrid Enrichment with 1048 ultra-conserved elements (UCEs) for 433 taxa including all extant families, >95% of all subfamilies, and 356 genera chosen to represent the vast diversity of the superfamily. Going back and forth between the molecular results and our collective knowledge of morphology and biology, we detected bias in the analyses that was driven by the saturation of nucleotide data. Our final results are based on a concatenated analysis of the least saturated exons and UCE datasets (2054 loci, 284 106 sites). Our analyses support an expected sister relationship with Mymarommatoidea. Seven previously recognized families were not monophyletic, so support for a new classification is discussed. Natural history in some cases would appear to be more informative than morphology, as illustrated by the elucidation of a clade of plant gall associates and a clade of taxa with planidial first-instar larvae. The phylogeny suggests a transition from smaller soft-bodied wasps to larger and more heavily sclerotized wasps, with egg parasitism as potentially ancestral for the entire superfamily. Deep divergences in Chalcidoidea coincide with an increase in insect families in the fossil record, and an early shift to phytophagy corresponds with the beginning of the "Angiosperm Terrestrial Revolution". Our dating analyses suggest a middle Jurassic origin of 174 Ma (167.3-180.5 Ma) and a crown age of 162.2 Ma (153.9-169.8 Ma) for Chalcidoidea. During the Cretaceous, Chalcidoidea may have undergone a rapid radiation in southern Gondwana with subsequent dispersals to the Northern Hemisphere. This scenario is discussed with regard to knowledge about the host taxa of chalcid wasps, their fossil record and Earth's palaeogeographic history.

More complex than you think: Taxonomic and temporal patterns of plant-pollinator networks of caraway (Carum carvi L.).

Caraway (Carum carvi L.) is a crop species that is gaining in importance in Europe, especially as a condiment and medicinal plant. Here, we present the plant-pollinator network of caraway in a central European agricultural landscape, focusing on two diverse potential pollinator taxa, Diptera: Brachycera (= true flies) and Hymenoptera (sawflies, bees, and wasps). We specifically studied qualitative differences in interactions between the two insect taxa as well as the intraday and intraseasonal variability of the network. Insect and pollen plant species determination was done via morphological identification and DNA (meta)barcoding. In total, 121 species representing 33 families of Hymenoptera and Brachycera were found to carry caraway pollen. These taxa included many nonhoneybee and nonhoverfly species, showing a wide taxonomic breadth of potential pollinators and a higher network complexity than previously anticipated. There are distinct qualitative differences between Brachycera and Hymenoptera networks, suggesting complementary roles of both taxa in the pollination of native and crop plants. Strong intraday differences in potential pollinator diversity make it necessary to collect insects and pollen at different times of the day to compile complete plant-pollinator networks. Intraseasonal analyses of the plant-pollinator network of caraway show the potential of caraway as an important food source for insect species with an activity peak in late summer.

Phylogenomics reveals the evolutionary timing and pattern of butterflies and moths.

Butterflies and moths (Lepidoptera) are one of the major superradiations of insects, comprising nearly 160,000 described extant species. As herbivores, pollinators, and prey, Lepidoptera play a fundamental role in almost every terrestrial ecosystem. Lepidoptera are also indicators of environmental change and serve as models for research on mimicry and genetics. They have been central to the development of coevolutionary hypotheses, such as butterflies with flowering plants and moths' evolutionary arms race with echolocating bats. However, these hypotheses have not been rigorously tested, because a robust lepidopteran phylogeny and timing of evolutionary novelties are lacking. To address these issues, we inferred a comprehensive phylogeny of Lepidoptera, using the largest dataset assembled for the order (2,098 orthologous protein-coding genes from transcriptomes of 186 species, representing nearly all superfamilies), and dated it with carefully evaluated synapomorphy-based fossils. The oldest members of the Lepidoptera crown group appeared in the Late Carboniferous (∼300 Ma) and fed on nonvascular land plants. Lepidoptera evolved the tube-like proboscis in the Middle Triassic (∼241 Ma), which allowed them to acquire nectar from flowering plants. This morphological innovation, along with other traits, likely promoted the extraordinary diversification of superfamily-level lepidopteran crown groups. The ancestor of butterflies was likely nocturnal, and our results indicate that butterflies became day-flying in the Late Cretaceous (∼98 Ma). Moth hearing organs arose multiple times before the evolutionary arms race between moths and bats, perhaps initially detecting a wide range of sound frequencies before being co-opted to specifically detect bat sonar. Our study provides an essential framework for future comparative studies on butterfly and moth evolution.

The evolution and genomic basis of beetle diversity.

The order Coleoptera (beetles) is arguably the most speciose group of animals, but the evolutionary history of beetles, including the impacts of plant feeding (herbivory) on beetle diversification, remain poorly understood. We inferred the phylogeny of beetles using 4,818 genes for 146 species, estimated timing and rates of beetle diversification using 89 genes for 521 species representing all major lineages and traced the evolution of beetle genes enabling symbiont-independent digestion of lignocellulose using 154 genomes or transcriptomes. Phylogenomic analyses of these uniquely comprehensive datasets resolved previously controversial beetle relationships, dated the origin of Coleoptera to the Carboniferous, and supported the codiversification of beetles and angiosperms. Moreover, plant cell wall-degrading enzymes (PCWDEs) obtained from bacteria and fungi via horizontal gene transfers may have been key to the Mesozoic diversification of herbivorous beetles-remarkably, both major independent origins of specialized herbivory in beetles coincide with the first appearances of an arsenal of PCWDEs encoded in their genomes. Furthermore, corresponding (Jurassic) diversification rate increases suggest that these novel genes triggered adaptive radiations that resulted in nearly half of all living beetle species. We propose that PCWDEs enabled efficient digestion of plant tissues, including lignocellulose in cell walls, facilitating the evolution of uniquely specialized plant-feeding habits, such as leaf mining and stem and wood boring. Beetle diversity thus appears to have resulted from multiple factors, including low extinction rates over a long evolutionary history, codiversification with angiosperms, and adaptive radiations of specialized herbivorous beetles following convergent horizontal transfers of microbial genes encoding PCWDEs.

Evolutionary history of Polyneoptera and its implications for our understanding of early winged insects.

Polyneoptera represents one of the major lineages of winged insects, comprising around 40,000 extant species in 10 traditional orders, including grasshoppers, roaches, and stoneflies. Many important aspects of polyneopteran evolution, such as their phylogenetic relationships, changes in their external appearance, their habitat preferences, and social behavior, are unresolved and are a major enigma in entomology. These ambiguities also have direct consequences for our understanding of the evolution of winged insects in general; for example, with respect to the ancestral habitats of adults and juveniles. We addressed these issues with a large-scale phylogenomic analysis and used the reconstructed phylogenetic relationships to trace the evolution of 112 characters associated with the external appearance and the lifestyle of winged insects. Our inferences suggest that the last common ancestors of Polyneoptera and of the winged insects were terrestrial throughout their lives, implying that wings did not evolve in an aquatic environment. The appearance of the first polyneopteran insect was mainly characterized by ancestral traits such as long segmented abdominal appendages and biting mouthparts held below the head capsule. This ancestor lived in association with the ground, which led to various specializations including hardened forewings and unique tarsal attachment structures. However, within Polyneoptera, several groups switched separately to a life on plants. In contrast to a previous hypothesis, we found that social behavior was not part of the polyneopteran ground plan. In other traits, such as the biting mouthparts, Polyneoptera shows a high degree of evolutionary conservatism unique among the major lineages of winged insects.

Beyond Drosophila: resolving the rapid radiation of schizophoran flies with phylotranscriptomics.

BACKGROUND: The most species-rich radiation of animal life in the 66 million years following the Cretaceous extinction event is that of schizophoran flies: a third of fly diversity including Drosophila fruit fly model organisms, house flies, forensic blow flies, agricultural pest flies, and many other well and poorly known true flies. Rapid diversification has hindered previous attempts to elucidate the phylogenetic relationships among major schizophoran clades. A robust phylogenetic hypothesis for the major lineages containing these 55,000 described species would be critical to understand the processes that contributed to the diversity of these flies. We use protein encoding sequence data from transcriptomes, including 3145 genes from 70 species, representing all superfamilies, to improve the resolution of this previously intractable phylogenetic challenge. RESULTS: Our results support a paraphyletic acalyptrate grade including a monophyletic Calyptratae and the monophyly of half of the acalyptrate superfamilies. The primary branching framework of Schizophora is well supported for the first time, revealing the primarily parasitic Pipunculidae and Sciomyzoidea stat. rev. as successive sister groups to the remaining Schizophora. Ephydroidea, Drosophila's superfamily, is the sister group of Calyptratae. Sphaeroceroidea has modest support as the sister to all non-sciomyzoid Schizophora. We define two novel lineages corroborated by morphological traits, the 'Modified Oviscapt Clade' containing Tephritoidea, Nerioidea, and other families, and the 'Cleft Pedicel Clade' containing Calyptratae, Ephydroidea, and other families. Support values remain low among a challenging subset of lineages, including Diopsidae. The placement of these families remained uncertain in both concatenated maximum likelihood and multispecies coalescent approaches. Rogue taxon removal was effective in increasing support values compared with strategies that maximise gene coverage or minimise missing data. CONCLUSIONS: Dividing most acalyptrate fly groups into four major lineages is supported consistently across analyses. Understanding the fundamental branching patterns of schizophoran flies provides a foundation for future comparative research on the genetics, ecology, and biocontrol.

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.

Correction to: An integrative phylogenomic approach to elucidate the evolutionary history and divergence times of Neuropterida (Insecta: Holometabola).

An amendment to this paper has been published and can be accessed via the original article.

An integrative phylogenomic approach to elucidate the evolutionary history and divergence times of Neuropterida (Insecta: Holometabola).

BACKGROUND: The latest advancements in DNA sequencing technologies have facilitated the resolution of the phylogeny of insects, yet parts of the tree of Holometabola remain unresolved. The phylogeny of Neuropterida has been extensively studied, but no strong consensus exists concerning the phylogenetic relationships within the order Neuroptera. Here, we assembled a novel transcriptomic dataset to address previously unresolved issues in the phylogeny of Neuropterida and to infer divergence times within the group. We tested the robustness of our phylogenetic estimates by comparing summary coalescent and concatenation-based phylogenetic approaches and by employing different quartet-based measures of phylogenomic incongruence, combined with data permutations. RESULTS: Our results suggest that the order Raphidioptera is sister to Neuroptera + Megaloptera. Coniopterygidae is inferred as sister to all remaining neuropteran families suggesting that larval cryptonephry could be a ground plan feature of Neuroptera. A clade that includes Nevrorthidae, Osmylidae, and Sisyridae (i.e. Osmyloidea) is inferred as sister to all other Neuroptera except Coniopterygidae, and Dilaridae is placed as sister to all remaining neuropteran families. Ithonidae is inferred as the sister group of monophyletic Myrmeleontiformia. The phylogenetic affinities of Chrysopidae and Hemerobiidae were dependent on the data type analyzed, and quartet-based analyses showed only weak support for the placement of Hemerobiidae as sister to Ithonidae + Myrmeleontiformia. Our molecular dating analyses suggest that most families of Neuropterida started to diversify in the Jurassic and our ancestral character state reconstructions suggest a primarily terrestrial environment of the larvae of Neuropterida and Neuroptera. CONCLUSION: Our extensive phylogenomic analyses consolidate several key aspects in the backbone phylogeny of Neuropterida, such as the basal placement of Coniopterygidae within Neuroptera and the monophyly of Osmyloidea. Furthermore, they provide new insights into the timing of diversification of Neuropterida. Despite the vast amount of analyzed molecular data, we found that certain nodes in the tree of Neuroptera are not robustly resolved. Therefore, we emphasize the importance of integrating the results of morphological analyses with those of sequence-based phylogenomics. We also suggest that comparative analyses of genomic meta-characters should be incorporated into future phylogenomic studies of Neuropterida.

An integrative phylogenomic approach illuminates the evolutionary history of cockroaches and termites (Blattodea).

Phylogenetic relationships among subgroups of cockroaches and termites are still matters of debate. Their divergence times and major phenotypic transitions during evolution are also not yet settled. We addressed these points by combining the first nuclear phylogenomic study of termites and cockroaches with a thorough approach to divergence time analysis, identification of endosymbionts, and reconstruction of ancestral morphological traits and behaviour. Analyses of the phylogenetic relationships within Blattodea robustly confirm previously uncertain hypotheses such as the sister-group relationship between Blaberoidea and remaining Blattodea, and Lamproblatta being the closest relative to the social and wood-feeding Cryptocercus and termites. Consequently, we propose new names for various clades in Blattodea: Cryptocercus + termites = Tutricablattae; Lamproblattidae + Tutricablattae = Kittrickea; and Blattoidea + Corydioidea = Solumblattodea. Our inferred divergence times contradict previous studies by showing that most subgroups of Blattodea evolved in the Cretaceous, reducing the gap between molecular estimates of divergence times and the fossil record. On a phenotypic level, the blattodean ground-plan is for egg packages to be laid directly in a hole while other forms of oviposition, including ovovivipary and vivipary, arose later. Finally, other changes in egg care strategy may have allowed for the adaptation of nest building and other novelties.

Phylogenomics of the superfamily Dytiscoidea (Coleoptera: Adephaga) with an evaluation of phylogenetic conflict and systematic error.

The beetle superfamily Dytiscoidea, placed within the suborder Adephaga, comprises six families. The phylogenetic relationships of these families, whose species are aquatic, remain highly contentious. In particular the monophyly of the geographically disjunct Aspidytidae (China and South Africa) remains unclear. Here we use a phylogenomic approach to demonstrate that Aspidytidae are indeed monophyletic, as we inferred this phylogenetic relationship from analyzing nucleotide sequence data filtered for compositional heterogeneity and from analyzing amino-acid sequence data. Our analyses suggest that Aspidytidae are the sister group of Amphizoidae, although the support for this relationship is not unequivocal. A sister group relationship of Hygrobiidae to a clade comprising Amphizoidae, Aspidytidae, and Dytiscidae is supported by analyses in which model assumptions are violated the least. In general, we find that both concatenation and the applied coalescent method are sensitive to the effect of among-species compositional heterogeneity. Four-cluster likelihood-mapping suggests that despite the substantial size of the dataset and the use of advanced analytical methods, statistical support is weak for the inferred phylogenetic placement of Hygrobiidae. These results indicate that other kinds of data (e.g. genomic meta-characters) are possibly required to resolve the above-specified persisting phylogenetic uncertainties. Our study illustrates various data-driven confounding effects in phylogenetic reconstructions and highlights the need for careful monitoring of model violations prior to phylogenomic analysis.

Phylogenomic analysis of Apoidea sheds new light on the sister group of bees.

BACKGROUND: Apoid wasps and bees (Apoidea) are an ecologically and morphologically diverse group of Hymenoptera, with some species of bees having evolved eusocial societies. Major problems for our understanding of the evolutionary history of Apoidea have been the difficulty to trace the phylogenetic origin and to reliably estimate the geological age of bees. To address these issues, we compiled a comprehensive phylogenomic dataset by simultaneously analyzing target DNA enrichment and transcriptomic sequence data, comprising 195 single-copy protein-coding genes and covering all major lineages of apoid wasps and bee families. RESULTS: Our compiled data matrix comprised 284,607 nucleotide sites that we phylogenetically analyzed by applying a combination of domain- and codon-based partitioning schemes. The inferred results confirm the polyphyletic status of the former family "Crabronidae", which comprises nine major monophyletic lineages. We found the former subfamily Pemphredoninae to be polyphyletic, comprising three distantly related clades. One of them, Ammoplanina, constituted the sister group of bees in all our analyses. We estimate the origin of bees to be in the Early Cretaceous (ca. 128 million years ago), a time period during which angiosperms rapidly radiated. Finally, our phylogenetic analyses revealed that within the Apoidea, (eu)social societies evolved exclusively in a single clade that comprises pemphredonine and philanthine wasps as well as bees. CONCLUSION: By combining transcriptomic sequences with those obtained via target DNA enrichment, we were able to include an unprecedented large number of apoid wasps in a phylogenetic study for tracing the phylogenetic origin of bees. Our results confirm the polyphyletic nature of the former wasp family Crabonidae, which we here suggest splitting into eight families. Of these, the family Ammoplanidae possibly represents the extant sister lineage of bees. Species of Ammoplanidae are known to hunt thrips, of which some aggregate on flowers and feed on pollen. The specific biology of Ammoplanidae as predators indicates how the transition from a predatory to pollen-collecting life style could have taken place in the evolution of bees. This insight plus the finding that (eu)social societies evolved exclusively in a single subordinated lineage of apoid wasps provides new perspectives for future comparative studies.

Transcriptome sequence-based phylogeny of chalcidoid wasps (Hymenoptera: Chalcidoidea) reveals a history of rapid radiations, convergence, and evolutionary success.

Chalcidoidea are a megadiverse group of mostly parasitoid wasps of major ecological and economical importance that are omnipresent in almost all extant terrestrial habitats. The timing and pattern of chalcidoid diversification is so far poorly understood and has left many important questions on the evolutionary history of Chalcidoidea unanswered. In this study, we infer the early divergence events within Chalcidoidea and address the question of whether or not ancestral chalcidoids were small egg parasitoids. We also trace the evolution of some key traits: jumping ability, development of enlarged hind femora, and associations with figs. Our phylogenetic inference is based on the analysis of 3,239 single-copy genes across 48 chalcidoid wasps and outgroups representatives. We applied an innovative a posteriori evaluation approach to molecular clock-dating based on nine carefully validated fossils, resulting in the first molecular clock-based estimation of deep Chalcidoidea divergence times. Our results suggest a late Jurassic origin of Chalcidoidea, with a first divergence of morphologically and biologically distinct groups in the early to mid Cretaceous, between 129 and 81 million years ago (mya). Diversification of most extant lineages happened rapidly after the Cretaceous in the early Paleogene, between 75 and 53 mya. The inferred Chalcidoidea tree suggests a transition from ancestral minute egg parasitoids to larger-bodied parasitoids of other host stages during the early history of chalcidoid evolution. The ability to jump evolved independently at least three times, namely in Eupelmidae, Encyrtidae, and Tanaostigmatidae. Furthermore, the large-bodied strongly sclerotized species with enlarged hind femora in Chalcididae and Leucospidae are not closely related. Finally, the close association of some chalcidoid wasps with figs, either as pollinators, or as inquilines/gallers or as parasitoids, likely evolved at least twice independently: in the Eocene, giving rise to fig pollinators, and in the Oligocene or Miocene, resulting in non-pollinating fig-wasps, including gallers and parasitoids. The origins of very speciose lineages (e.g., Mymaridae, Eulophidae, Pteromalinae) are evenly spread across the period of chalcidoid evolution from early Cretaceous to the late Eocene. Several shifts in biology and morphology (e.g., in host exploitation, body shape and size, life history), each followed by rapid radiations, have likely enabled the evolutionary success of Chalcidoidea.

Orthograph: a versatile tool for mapping coding nucleotide sequences to clusters of orthologous genes.

BACKGROUND: Orthology characterizes genes of different organisms that arose from a single ancestral gene via speciation, in contrast to paralogy, which is assigned to genes that arose via gene duplication. An accurate orthology assignment is a crucial step for comparative genomic studies. Orthologous genes in two organisms can be identified by applying a so-called reciprocal search strategy, given that complete information of the organisms' gene repertoire is available. In many investigations, however, only a fraction of the gene content of the organisms under study is examined (e.g., RNA sequencing). Here, identification of orthologous nucleotide or amino acid sequences can be achieved using a graph-based approach that maps nucleotide sequences to genes of known orthology. Existing implementations of this approach, however, suffer from algorithmic issues that may cause problems in downstream analyses. RESULTS: We present a new software pipeline, Orthograph, that addresses and solves the above problems and implements useful features for a wide range of comparative genomic and transcriptomic analyses. Orthograph applies a best reciprocal hit search strategy using profile hidden Markov models and maps nucleotide sequences to the globally best matching cluster of orthologous genes, thus enabling researchers to conveniently and reliably delineate orthologs and paralogs from transcriptomic and genomic sequence data. We demonstrate the performance of our approach on de novo-sequenced and assembled transcript libraries of 24 species of apoid wasps (Hymenoptera: Aculeata) as well as on published genomic datasets. CONCLUSION: With Orthograph, we implemented a best reciprocal hit approach to reference-based orthology prediction for coding nucleotide sequences such as RNAseq data. Orthograph is flexible, easy to use, open source and freely available at https://mptrsen.github.io/Orthograph . Additionally, we release 24 de novo-sequenced and assembled transcript libraries of apoid wasp species.

The molecular evolutionary dynamics of oxidative phosphorylation (OXPHOS) genes in Hymenoptera.

BACKGROUND: The primary energy-producing pathway in eukaryotic cells, the oxidative phosphorylation (OXPHOS) system, comprises proteins encoded by both mitochondrial and nuclear genes. To maintain the function of the OXPHOS system, the pattern of substitutions in mitochondrial and nuclear genes may not be completely independent. It has been suggested that slightly deleterious substitutions in mitochondrial genes are compensated by substitutions in the interacting nuclear genes due to positive selection. Among the four largest insect orders, Coleoptera (beetles), Hymenoptera (sawflies, wasps, ants, and bees), Diptera (midges, mosquitoes, and flies) and Lepidoptera (moths and butterflies), the mitochondrial genes of Hymenoptera exhibit an exceptionally high amino acid substitution rate while the evolution of nuclear OXPHOS genes is largely unknown. Therefore, Hymenoptera is an excellent model group for testing the hypothesis of positive selection driving the substitution rate of nuclear OXPHOS genes. In this study, we report the evolutionary rate of OXPHOS genes in Hymenoptera and test for evidence of positive selection in nuclear OXPHOS genes of Hymenoptera. RESULTS: Our analyses revealed that the amino acid substitution rate of mitochondrial and nuclear OXPHOS genes in Hymenoptera is higher than that in other studied insect orders. In contrast, the amino acid substitution rate of non-OXPHOS genes in Hymenoptera is lower than the rate in other insect orders. Overall, we found the dN/dS ratio of the nuclear OXPHOS genes to be higher in Hymenoptera than in other insect orders. However, nuclear OXPHOS genes with high dN/dS ratio did not always exhibit a high amino acid substitution rate. Using branch-site and site model tests, we identified various codon sites that evolved under positive selection in nuclear OXPHOS genes. CONCLUSIONS: Our results showed that nuclear OXPHOS genes in Hymenoptera are evolving faster than the genes in other three insect orders. The branch test suggested that while some nuclear OXPHOS genes in Hymenoptera show a signature of positive selection, the pattern is not consistent across all nuclear OXPHOS genes. As only few codon sites were under positive selection, we suggested that positive selection might not be the only factor contributing to the rapid evolution of nuclear OXPHOS genes in Hymenoptera.

BaitFisher: A Software Package for Multispecies Target DNA Enrichment Probe Design.

Target DNA enrichment combined with high-throughput sequencing technologies is a powerful approach to probing a large number of loci in genomes of interest. However, software algorithms that explicitly consider nucleotide sequence information of target loci in multiple reference species for optimizing design of target enrichment baits to be applicable across a wide range of species have not been developed. Here we present an algorithm that infers target DNA enrichment baits from multiple nucleotide sequence alignments. By applying clustering methods and the combinatorial 1-center sequence optimization to bait design, we are able to minimize the total number of baits required to efficiently probe target loci in multiple species. Consequently, more loci can be probed across species with a given number of baits. Using transcript sequences of 24 apoid wasps (Hymenoptera: Crabronidae, Sphecidae) from the 1KITE project and the gene models of Nasonia vitripennis, we inferred 57,650, 120-bp-long baits for capturing 378 coding sequence sections of 282 genes in apoid wasps. Illumina reduced-representation library sequencing confirmed successful enrichment of the target DNA when applying these baits to DNA of various apoid wasps. The designed baits furthermore enriched a major fraction of the target DNA in distantly related Hymenoptera, such as Formicidae and Chalcidoidea, highlighting the baits' broad taxonomic applicability. The availability of baits with broad taxonomic applicability is of major interest in numerous disciplines, ranging from phylogenetics to biodiversity monitoring. We implemented our new approach in a software package, called BaitFisher, which is open source and freely available at https://github.com/cmayer/BaitFisher-package.git.

Transcriptome and target DNA enrichment sequence data provide new insights into the phylogeny of vespid wasps (Hymenoptera: Aculeata: Vespidae).

The wasp family Vespidae comprises more than 5000 described species which represent life history strategies ranging from solitary and presocial to eusocial and socially parasitic. The phylogenetic relationships of the major vespid wasp lineages (i.e., subfamilies and tribes) have been investigated repeatedly by analyzing behavioral and morphological traits as well as nucleotide sequences of few selected genes with largely incongruent results. Here we reconstruct their phylogenetic relationships using a phylogenomic approach. We sequenced the transcriptomes of 24 vespid wasp and eight outgroup species and exploited the transcript sequences for design of probes for enriching 913 single-copy protein-coding genes to complement the transcriptome data with nucleotide sequence data from additional 25 ethanol-preserved vespid species. Results from phylogenetic analyses of the combined sequence data revealed the eusocial subfamily Stenogastrinae to be the sister group of all remaining Vespidae, while the subfamily Eumeninae turned out to be paraphyletic. Of the three currently recognized eumenine tribes, Odynerini is paraphyletic with respect to Eumenini, and Zethini is paraphyletic with respect to Polistinae and Vespinae. Our results are in conflict with the current tribal subdivision of Eumeninae and thus, we suggest granting subfamily rank to the two major clades of "Zethini": Raphiglossinae and Zethinae. Overall, our findings corroborate the hypothesis of two independent origins of eusociality in vespid wasps and suggest a single origin of using masticated and salivated plant material for building nests by Raphiglossinae, Zethinae, Polistinae, and Vespinae. The inferred phylogenetic relationships and the open access vespid wasp target DNA enrichment probes will provide a valuable tool for future comparative studies on species of the family Vespidae, including their genomes, life styles, evolution of sociality, and co-evolution with other organisms.

New Insights into the Evolution of the W Chromosome in Lepidoptera.

Moths and butterflies (Lepidoptera) represent the most diverse group of animals with heterogametic females. Although the vast majority of species has a WZ/ZZ (female/male) sex chromosome system, it is generally accepted that the ancestral system was Z/ZZ and the W chromosome has evolved in a common ancestor of Tischeriidae and Ditrysia. However, the lack of data on sex chromosomes in lower Lepidoptera has prevented a formal test of this hypothesis. Here, we performed a detailed analysis of sex chromosomes in Tischeria ekebladella (Tischeriidae) and 3 species representing lower Ditrysia, Cameraria ohridella (Gracillariidae), Plutella xylostella (Plutellidae), and Tineola bisselliella (Tineidae). Using comparative genomic hybridization we show that the first 3 species have well-differentiated W chromosomes, which vary considerably in their molecular composition, whereas T. bisselliella has no W chromosome. Furthermore, our results suggest the presence of neo-sex chromosomes in C. ohridella. For Z chromosomes, we selected 5 genes evenly distributed along the Z chromosome in ditrysian model species and tested their Z-linkage using qPCR. The tested genes (Henna, laminin A, Paramyosin, Tyrosine hydroxylase, and 6-Phosphogluconate dehydrogenase) proved to be Z-linked in all species examined. The conserved synteny of the Z chromosome across Tischeriidae and Ditrysia, along with the W chromosome absence in the lower ditrysian families Psychidae and Tineidae, suggests a possible independent origin of the W chromosomes in these 2 lineages.

Transcriptomic data from panarthropods shed new light on the evolution of insulator binding proteins in insects : Insect insulator proteins.

BACKGROUND: Body plan development in multi-cellular organisms is largely determined by homeotic genes. Expression of homeotic genes, in turn, is partially regulated by insulator binding proteins (IBPs). While only a few enhancer blocking IBPs have been identified in vertebrates, the common fruit fly Drosophila melanogaster harbors at least twelve different enhancer blocking IBPs. We screened recently compiled insect transcriptomes from the 1KITE project and genomic and transcriptomic data from public databases, aiming to trace the origin of IBPs in insects and other arthropods. RESULTS: Our study shows that the last common ancestor of insects (Hexapoda) already possessed a substantial number of IBPs. Specifically, of the known twelve insect IBPs, at least three (i.e., CP190, Su(Hw), and CTCF) already existed prior to the evolution of insects. Furthermore we found GAF orthologs in early branching insect orders, including Zygentoma (silverfish and firebrats) and Diplura (two-pronged bristletails). Mod(mdg4) is most likely a derived feature of Neoptera, while Pita is likely an evolutionary novelty of holometabolous insects. Zw5 appears to be restricted to schizophoran flies, whereas BEAF-32, ZIPIC and the Elba complex, are probably unique to the genus Drosophila. Selection models indicate that insect IBPs evolved under neutral or purifying selection. CONCLUSIONS: Our results suggest that a substantial number of IBPs either pre-date the evolution of insects or evolved early during insect evolution. This suggests an evolutionary history of insulator binding proteins in insects different to that previously thought. Moreover, our study demonstrates the versatility of the 1KITE transcriptomic data for comparative analyses in insects and other arthropods.