Recalibration of the insect evolutionary time scale using Monte San Giorgio fossils suggests survival of key lineages through the End-Permian Extinction

A winged relative of ice-crawlers in amber bridges the cryptic extant Xenonomia and a rich fossil record

Until the advent of phylogenomics, the atypical morphology of extant representatives of the insect orders Grylloblattodea (ice-crawlers) and Mantophasmatodea (gladiators) had confounding effects on efforts to resolve their placement within Polyneoptera. This recent research has unequivocally shown that these species-poor groups are closely related and form the clade Xenonomia. Nonetheless, divergence dates of these groups remain poorly constrained, and their evolutionary history debated, as the few well-identified fossils, characterized by a suite of morphological features similar to that of extant forms, are comparatively young. Notably, the extant forms of both groups are wingless, whereas most of the pre-Cretaceous insect fossil record is composed of winged insects, which represents a major shortcoming of the taxonomy. Here, we present new specimens embedded in mid-Cretaceous amber from Myanmar and belonging to the recently described species Aristovia daniili. The abundant material and pristine preservation allowed a detailed documentation of the morphology of the species, including critical head features. Combined with a morphological data set encompassing all Polyneoptera, these new data unequivocally demonstrate that A. daniili is a winged stem Grylloblattodea. This discovery demonstrates that winglessness was acquired independently in Grylloblattodea and Mantophasmatodea. Concurrently, wing apomorphic traits shared by the new fossil and earlier fossils demonstrate that a large subset of the former "Protorthoptera" assemblage, representing a third of all known insect species in some Permian localities, are genuine representatives of Xenonomia. Data from the fossil record depict a distinctive evolutionary trajectory, with the group being both highly diverse and abundant during the Permian but experiencing a severe decline from the Triassic onwards.

Geologically calibrated mammalian tree and its correlation with global events, including the emergence of humans

A robust timetree for Mammalia was constructed using the time calibration function of BEAST v1.10.4 and MEGA 11. The analysis involved the application of times of the most recent common ancestors, including a total of 19 mammalian fossil calibration ages following Benton et al. (Palaeontologia Electronica, 2015, 1-106) for their minimum ages. Additionally, fossil calibration ages for Gorilla, Pan, and a geologic event calibration age for otters were incorporated. Using these calibration ages, I constructed a geologically calibrated tree that estimates the age of the Homo and Pan splitting to be 5.69 Ma. The tree carries several significant implications. First, after the initial rifting at 120 Ma, the Atlantic Ocean expanded by over 500 km around Chron 34 (84 Ma), and vicariant speciation between Afrotheria (Africa) and Xenarthra (South America) appears to have commenced around 70 Ma. Additionally, ordinal level differentiations began immediately following the K-Pg boundary (66.0 Ma), supporting previous hypothesis that mammalian radiation rapidly filled ecological niches left vacant by non-avian dinosaurs. I constructed a diagram depicting the relationship between base substitution rate and age using an additional function in BEAST v1.10.4. The diagram reveals an exponential increase in the base substitution rate approaching recent times. This increased base substitution rate during the Neogene period may have contributed to the expansion of biodiversity, including the extensive adaptive radiation that led to the evolution of Homo sapiens. One significant driving factor behind this radiation could be attributed to the emergence and proliferation of C4 grasses since 20 Ma. These grasses have played a role in increasing carbon fixation, reducing atmospheric CO2 concentration, inducing global cooling, and initiating Quaternary glacial-interglacial cycles, thereby causing significant climatic changes.

Illusion of flight? Absence, evidence and the age of winged insects

The earliest fossils of winged insects (Pterygota) are mid-Carboniferous (latest Mississippian, 328–324 Mya), but estimates of their age based on fossil-calibrated molecular phylogenetic studies place their origin at 440–370 Mya during the Silurian or Devonian. This discrepancy would require that winged insects evaded fossilization for at least the first ~50 Myr of their history. Here, we examine the plausibility of such a gap in the fossil record, and possible explanations for it, based on comparisons with the fossil records of other arthropod groups, the distribution of first occurrence dates of pterygote families, phylogenetically informed simulations of the fossilization of Palaeozoic insects, and re-analysis of data presented by Misof and colleagues using updated fossil calibrations under a variety of prior probability settings. We do not find support for the mechanisms previously suggested to account for such an extended gap in the pterygote fossil record, including sampling bias, preservation bias, and body size. We suggest that inference of an early origin of Pterygota long prior to their first appearance in the fossil record is probably an analytical artefact of taxon sampling and choice of fossil calibration points, possibly compounded by heterogeneity in rates of sequence evolution or speciation, including radiations or ‘bursts’ during their early history.

Multiple drivers and lineage-specific insect extinctions during the Permo-Triassic

The Permo-Triassic interval encompasses three extinction events including the most dramatic biological crisis of the Phanerozoic, the latest Permian mass extinction. However, their drivers and outcomes are poorly quantified and understood for terrestrial invertebrates, which we assess here for insects. We find a pattern with three extinctions: the Roadian/Wordian (≈266.9 Ma; extinction of 64.5% insect genera), the Permian/Triassic (≈252 Ma; extinction of 82.6% insect genera), and the Ladinian/Carnian boundaries (≈237 Ma; extinction of 74.8% insect genera). We also unveil a heterogeneous effect of these extinction events across the major insect clades. Because extinction events have impacted Permo-Triassic ecosystems, we investigate the influence of abiotic and biotic factors on insect diversification dynamics and find that changes in floral assemblages are likely the strongest drivers of insects' responses throughout the Permo-Triassic. We also assess the effect of diversity dependence between three insect guilds; an effect ubiquitously found in current ecosystems. We find that herbivores held a central position in the Permo-Triassic interaction network. Our study reveals high levels of insect extinction that profoundly shaped the evolutionary history of the most diverse non-microbial lineage.

A world review of the bristle fly parasitoids of webspinners

Background

Dipteran parasitoids of Embioptera (webspinners) are few and extremely rare but known from all biogeographical regions except Australasia/Oceania. All belong to the fly family Tachinidae, a hyperdiverse and widespread clade of parasitoids attacking a variety of arthropod orders.

Results

The webspinner-parasitizing Diptera are reviewed based mostly on records from the collecting and rearing by Edward S. Ross. A new genus is erected to accommodate a new Afrotropical species, Embiophoneus rossi gen. et sp. nov. The genus Perumyia Arnaud is reviewed and a new species, Perumyia arnaudi sp. nov., is described from Central America while P. embiaphaga Arnaud is redescribed and new host records are given. A new species of Phytomyptera Rondani, P. woodi sp. nov., is described from Myanmar, representing the first report of a member of this genus obtained from webspinners. The genus Rossimyiops Mesnil is reviewed, R. longicornis (Kugler) is redescribed and R. aeratus sp. nov., R. fuscus sp. nov. and R. rutilans sp. nov. are newly described from the Oriental Region, and an updated key to species is given.

Conclusions

Webspinners were probably colonized independently at least four times by tachinids shifting from other hosts, most likely Lepidoptera.

Gene arrangement, phylogeny and divergence time estimation of mitogenomes in Thrips

BACKGROUND

The metazoan mitogenomes usually display conserved gene arrangement while thrips are known for their extensive gene rearrangement, and duplication of the control region.

METHODS AND RESULT

We sequenced complete mitogenomes of eight species of thrips to determine the gene arrangement, phylogeny and divergence time estimation. All contain 37 genes and one control region, (CR) except four species with two CRs. Duplicated tRNAs were detected in Mycterothrips nilgiriensis and Thrips florum. nad4-nad4L were not found adjacent to each other in Phibalothrips peringueyi and Plicothrips apicalis. Both Bayesian and likelihood phylogenetic analyses of thrips mitogenomes supported the monophyly of two suborders (Terebrantia and Tubulifera) and the two largest families (Phlaeothripidae and Thripidae). Out of seven earlier proposed ancestral gene blocks, six are conserved in Panchaetothripinae, three in Thripinae and two in Phlaeothripidae. Additionally, eight Thrips Gene Blocks were identified, of which, three conserved in Tubulifera, four in Terebrantia, and one only in Aeolothripidae. Forty-two gene boundaries (15 from previous study + 27 new) were identified. The molecular divergence time is estimated for the order Thysanoptera and suggested that these insects may have been diversified from hemipterans in the late Permian period. The most recent ancestors belong to family Thripidae and Phlaeothripidae, which were diversified in upper Cretaceous period and showed higher rates of rearrangement from the ancestral gene order.

CONCLUSIONS

The current study is the first largest effort to provide the new insights into the mitogenomic features, gene arrangement, phylogeny and divergence time estimation of thrips belonging to the order Thysanoptera.

What is the age of flowering plants?

The origin of flowering plants (angiosperms) was one of the most transformative events in the history of our planet. Despite considerable interest from multiple research fields, numerous questions remain, including the age of the group as a whole. Recent studies have reported a perplexing range of estimates for the crown-group age of angiosperms, from ~140 million years (Ma; Early Cretaceous) to 270 Ma (Permian). Both ends of the spectrum are now supported by both macroevolutionary analyses of the fossil record and fossil-calibrated molecular dating analyses. Here, we first clarify and distinguish among the three ages of angiosperms: the age of their divergence with acrogymnosperms (stem age); the age(s) of emergence of their unique, distinctive features including flowers (morphological age); and the age of the most recent common ancestor of all their living species (crown age). We then demonstrate, based on recent studies, that fossil-calibrated molecular dating estimates of the crown-group age of angiosperms have little to do with either the amount of molecular data or the number of internal fossil calibrations included. Instead, we argue that this age is almost entirely conditioned by its own prior distribution (typically a calibration density set by the user in Bayesian analyses). Lastly, we discuss which future discoveries or novel types of analyses are most likely to bring more definitive answers. In the meantime, we propose that the age of angiosperms is best described as largely unknown (140-270 Ma) and that contrasting age estimates in the literature mostly reflect conflicting prior distributions. We also suggest that future work that depends on the time scale of flowering plant diversification be designed to integrate over this vexing uncertainty.

Ecological radiations of insects in the Mesozoic

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

The Angiosperm Terrestrial Revolution and the origins of modern biodiversity

Biodiversity today has the unusual property that 85% of plant and animal species live on land rather than in the sea, and half of these live in tropical rainforests. An explosive boost to terrestrial diversity occurred from c. 100-50 million years ago, the Late Cretaceous and early Palaeogene. During this interval, the Earth-life system on land was reset, and the biosphere expanded to a new level of productivity, enhancing the capacity and species diversity of terrestrial environments. This boost in terrestrial biodiversity coincided with innovations in flowering plant biology and evolutionary ecology, including their flowers and efficiencies in reproduction; coevolution with animals, especially pollinators and herbivores; photosynthetic capacities; adaptability; and ability to modify habitats. The rise of angiosperms triggered a macroecological revolution on land and drove modern biodiversity in a secular, prolonged shift to new, high levels, a series of processes we name here the Angiosperm Terrestrial Revolution.

Early evolution of beetles regulated by the end-Permian deforestation

The end-Permian mass extinction (EPME) led to a severe terrestrial ecosystem collapse. However, the ecological response of insects—the most diverse group of organisms on Earth—to the EPME remains poorly understood. Here, we analyse beetle evolutionary history based on taxonomic diversity, morphological disparity, phylogeny, and ecological shifts from the Early Permian to Middle Triassic, using a comprehensive new dataset. Permian beetles were dominated by xylophagous stem groups with high diversity and disparity, which probably played an underappreciated role in the Permian carbon cycle. Our suite of analyses shows that Permian xylophagous beetles suffered a severe extinction during the EPME largely due to the collapse of forest ecosystems, resulting in an Early Triassic gap of xylophagous beetles. New xylophagous beetles appeared widely in the early Middle Triassic, which is consistent with the restoration of forest ecosystems. Our results highlight the ecological significance of insects in deep-time terrestrial ecosystems.

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.

Fossil and phylogenetic analyses reveal recurrent periods of diversification and extinction in dictyopteran insects

Variations of speciation and extinction rates determine the fate of clades through time. Periods of high diversification and extinction (possibly mass-extinction events) can punctuate the evolutionary history of various clades, but they remain loosely defined for many biological groups, especially nonmarine invertebrates like insects. Here, we examine whether the cockroaches, mantises and termites (altogether included in Dictyoptera) have experienced episodic pulses of speciation or extinction and how these pulses may be associated with environmental fluctuations or mass extinctions. We relied on molecular phylogeny and fossil data to shed light on the times and rates at which dictyopterans diversified. The diversification of Dictyoptera has alternated between (i) periods of high diversification in the late Carboniferous, Early-Middle Triassic, Early Cretaceous and middle Palaeogene, and (ii) periods of high extinction rates particularly at the Permian-Triassic boundary, but not necessarily correlated with the major global biodiversity crises as in the mid-Cretaceous. This study advocates the importance of analyzing, when possible, both molecular phylogeny and fossil data to unveil diversification and extinction periods for a given group. The causes and consequences of extinction must be studied beyond mass-extinction events alone to gain a broader understanding of how clades wax and wane.

The ecology of marine colonization by terrestrial arthropods

Terrestrial arthropods often colonized and became important in freshwater ecosystems, but did so less often and with little consequence in marine habitats. This pattern cannot be explained by the physical properties of water alone or by limitations of the terrestrial arthropod body plan alone. One hypothesis is that transitions among terrestrial, aquatic and marine ecosystems are unlikely when well-adapted incumbent species in the recipient realm collectively resist entry by initially less well adapted newcomers. I evaluated and modified this hypothesis by examining the properties of donor and recipient ecosystems and the roles that insects play or do not play in each. I argue that the insularity and diminished competitiveness of most freshwater ecosystems makes them vulnerable to invasion from land and sea, and largely prevent transitions from freshwater to terrestrial and marine habitats by arthropods. Small terrestrial arthropods emphasize high locomotor performance and long-distance communication, traits that work less well in the denser, more viscous medium of water. These limitations pose particular challenges for insects colonizing highly escalated marine ecosystems, where small incumbent species rely more on passive than on active defences. Predatory insects are less constrained than herbivores, wood-borers, filter-feeders, sediment burrowers and social species.

Molecular Phylogeny and Infraordinal Classification of Zoraptera (Insecta)

Zoraptera is a small and predominantly tropical insect order with an unresolved higher classification due to the extremely uniform external body morphology. We, therefore, conducted a multigene molecular phylogeny of extant Zoraptera and critically re-evaluated their morphological characters in order to propose a natural infraordinal classification. We recovered a highly-resolved phylogeny with two main clades representing major evolutionary lineages in Zoraptera, for which we propose family ranks. The two families exhibit striking differences in male genitalia and reproductive strategies. Each family contains two subclades (subfamilies) supported by several morphological synapomorphies including the relative lengths of the basal antennomeres, the number and position of metatibial spurs, and the structure of male genitalia. The newly proposed higher classification of Zoraptera includes the family Zorotypidae stat. revid. with Zorotypinae Silvestri, 1913 (Zorotypus stat. revid., Usazoros Kukalova-Peck and Peck, 1993 stat. restit.) and Spermozorinae subfam. nov. (Spermozoros gen. nov.), and Spriralizoridae fam. nov. with Spiralizorinae subfam. nov. (Spiralizoros gen. nov., Scapulizoros gen. nov., Cordezoros gen. nov., Centrozoros Kukalova-Peck and Peck, 1993, stat. restit., Brazilozoros Kukalova-Peck and Peck, 1993, stat. restit.), and Latinozorinae subfam. nov. (Latinozoros Kukalova-Peck and Peck, 1993, stat. restit.). An identification key and morphological diagnoses for all supraspecific taxa are provided.