Grylloblattodea Research Articles

Has past climate change affected cold‐specialized species differentially through space and time?

AbstractQuaternary climate change has been strongly linked to distributional shifts and recent species diversification. Montane species, in particular, have experienced enhanced isolation and rapid genetic divergence during glacial fluctuations, and these processes have resulted in a disproportionate number of neo‐endemic species forming in high‐elevation habitats. In temperate montane environments, a general model of alpine population history is well supported, where cold‐specialized species track favourable climate conditions downslope during glacial episodes and upslope during warmer interglacial periods, which leads to a climate‐driven population or species diversification pump. However, it remains unclear how geography mediates distributional changes and whether certain episodes of glacial history have differentially impacted rates of diversification. We address these questions by examining phylogenomic data in a North American clade of flightless, cold‐specialized insects, the ice crawlers (Insecta: Grylloblattodea: Grylloblattidae: Grylloblatta). These low‐vagility organisms have the potential to reveal highly localized refugia and patterns of spatial recolonization, as well as a longer history of in situ diversification. Using continuous phylogeographic analysis of species groups, we show that all species tend to retreat to nearby low‐elevation habitats across western North America during episodes of glaciation, but species at high latitude exhibit larger distributional shifts. Lineage diversification was examined over the course of the Neogene and Quaternary periods, with statistical analysis supporting a direct association between climate variation and diversification rate. Major increases in lineage diversification appear to be correlated with warm and dry periods, rather than with extreme glacial events. Finally, we identify substantial cryptic diversity among ice crawlers, leading to high endemism across their range. This diversity provides new insights into highly localized glacial refugia for cold‐specialized species across western North America.

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

BackgroundSecondary 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.ResultsWe 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.ConclusionsBased 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0612-5) contains supplementary material, which is available to authorized users.

The thorax of Mantophasmatodea, the morphology of flightlessness, and the evolution of the neopteran insects.

Mantophasmatodea was described as a new insect order in 2002. Since then, this small group of wingless insects has developed into one of the best investigated insect taxa. Nevertheless, many aspects of mantophasmatodean morphology as well as their evolutionary relationships remain ambiguous. To determine the phylogenetic relationships of Mantophasmatodea based on an extended character set and to elucidate possible morphological adaptions towards flightlessness, we investigated the thoracic morphology of two species, Austrophasma caledonensis and Mantophasma sp. The morphological similarity between these two species is striking and no differences in musculature were found. The mantophasmatodean thorax strongly resembles that of ice crawlers (Grylloblattodea), especially with respect to the presence of pleural processes in the meso- and metathorax, branched furcae in all segments, and similar muscle equipment. In a cladistic analysis containing all major lineages of Neoptera, the monophyly of Polyneoptera is supported by the presence of an anal fan and several modifications of the wing joint. Within Polyneoptera, a sister-group relationship between stoneflies and the remaining Polyneoptera is supported. A clade comprising Mantophasmatodea and the Grylloblattodea gains strong support from thoracic morphology and can be considered assured. Potential thoracic apomorphies include prothoracic paracoxal invaginations, pterothoracic pleural arms that originate from the epimeron, and a unique metathoracic sterno-coxal musculature. The monophyly of Orthoptera and Dictyoptera is further supported while the deeper polyneopteran nodes remain unresolved. Among the wingless taxa investigated we found few general morphological adaptations whereas, in other aspects, especially in the musculature, strong differences could be observed. However, much more research on the strongly neglected topic of flightlessness is required to make reliable statements.

Ice Crawlers (Grylloblattodea) – the history of the investigation of a highly unusual group of insects

Grylloblattodea are one of the most unusual groups of insects and the second smallest order. All known extant species are wingless and exhibit a remarkable preference for cold temperatures. Although their morphology was intensively investigated shortly after their discovery, the systematic position has been disputed for a long time. The placement of Grylloblattodea as sister-group to the recently described Mantophasamtodea is supported by morphological and molecular evidence. However, the relationships of this clade, Xenonomia, among the polyneopteran lineages is not clear. Transcriptome analyses, in addition to the study of winged grylloblattodean fossils, may help to clarify the position of Xenonomia and aid in the reconstruction of the “phylogenetic backbone” of Polyneoptera.

A second new species of ice crawlers from China (Insecta: Grylloblattodea), with thorax evolution and the prediction of potential distribution.

Modern grylloblattids are one of the least diverse of the modern insect orders. The thorax changes in morphology might be associated with the changes of the function of the forelegs, wing loss, changes in behavior and adaptation to habitat. As temperature is the main barrier for migration of modern grylloblattids, the range of each species is extremely limited. The potential distribution areas of grylloblattids remain unclear. A second new species of ice crawlers (Insecta: Grylloblattodea), Grylloblattella cheni Bai, Wang et Yang sp. nov., is described from China. The distribution map and key to species of Grylloblattella are given. A comparison of the thorax of extant and extinct Grylloblattodea is presented, with an emphasis on the pronotum using geometric morphometric analysis, which may reflect thorax adaptation and the evolution of Grylloblattodea. Potential global distribution of grylloblattids is inferred. Highly diversified pronota of extinct Grylloblattodea may reflect diverse habitats and niches. The relatively homogeneous pronota of modern grylloblattids might be explained by two hypotheses: synapomorphy or convergent evolution. Most fossils of Grylloblattodea contain an obviously longer meso- and metathorax than prothorax. The length of the meso- and metathorax of modern grylloblattids is normally shorter than the prothorax. This may be associated with the wing loss, which is accompanied by muscle reduction and changes to the thoracic skeleton system. Threats to grylloblattids and several conservation comments are also provided.

Phylogeny and biogeography of ice crawlers (Insecta: Grylloblattodea) based on six molecular loci: Designating conservation status for Grylloblattodea species

Ice crawlers (Insecta: Grylloblattodea) are rarely encountered insects that consist of five genera representing 26 species from North America and Asia. Asian grylloblattids are the most diverse, but North American ice crawlers (genus Grylloblatta) are known for their adaptation to cold conditions. Phylogenetic relationships among grylloblattid species and genera are not known. Six genes were sampled in 35 individuals for 18S rRNA, 28S rRNA, histone 3, 12S rRNA, 16S rRNA, and cytochrome oxidase II from 21 populations of Grylloblatta, three populations from Japan (genus Galloisiana), and three populations from Russia (genus Grylloblattina). Phylogenetic analysis of these data with two mantophasmid outgroups in POY supported monophyletic genera, with Grylloblatta as sister to Grylloblattina. Grylloblatta was shown to contain two major lineages: a clade in Northern California and Oregon and a clade in Washington and Oregon. One new species and six candidate species are proposed. IUCN Red List Conservation Criteria were implemented to designate conservation status for each lineage.