The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Sean D. Schoville - One of the best experts on this subject based on the ideXlab platform.
-
Comparative transcriptomics of ice-crawlers demonstrates cold specialization constrains niche evolution in a relict lineage.
Evolutionary applications, 2020Co-Authors: Sean D. Schoville, Sabrina Simon, Ryuichiro Machida, Ming Bai, Zachary Beethem, Roman Yu. Dudko, Monika J. B. Eberhard, Paul B. Frandsen, Simon C. Küpper, Max VerheijAbstract:Key changes in ecological niche space are often critical to understanding how lineages diversify during adaptive radiations. However, the converse, or understanding why some lineages are depauperate and relictual, is more challenging, as many factors may constrain niche evolution. In the case of the insect order Grylloblattodea, highly conserved thermal breadth is assumed to be closely tied to their relictual status, but has not been formerly tested. Here, we investigate whether evolutionary constraints in the physiological tolerance of temperature can help explain relictualism in this lineage. Using a comparative transcriptomics approach, we investigate gene expression following acute heat and cold stress across members of Grylloblattodea and their sister group, Mantophasmatodea. We additionally examine patterns of protein evolution, to identify candidate genes of positive selection. We demonstrate that cold specialization in Grylloblattodea has been accompanied by the loss of the inducible heat shock response under both acute heat and cold stress. Additionally, there is widespread evidence of selection on protein-coding genes consistent with evolutionary constraints due to cold specialization. This includes positive selection on genes involved in trehalose transport, metabolic function, mitochondrial function, oxygen reduction, oxidative stress, and protein synthesis. These patterns of molecular adaptation suggest that Grylloblattodea have undergone evolutionary trade-offs to survive in cold habitats and should be considered highly vulnerable to climate change. Finally, our transcriptomic data provide a robust backbone phylogeny for generic relationships within Grylloblattodea and Mantophasmatodea. Major phylogenetic splits in each group relate to arid conditions driving biogeographical patterns, with support for a sister-group relationship between North American Grylloblatta and Altai-Sayan Grylloblattella, and a range disjunction in Namibia splitting major clades within Mantophasmatodea.
-
Grylloblattodea of Canada.
ZooKeys, 2019Co-Authors: Sean D. SchovilleAbstract:The enigmatic insect order Grylloblattodea comprises two described species in Canada, which are limited to the Montane Cordillera and Pacific Maritime ecozones. One of the described species has three Canadian subspecies of uncertain taxonomic ranking, and there are two additional undescribed or unreported species known in close proximity to the Canadian border in western Alberta and British Columbia that likely also occur in Canada. Thus, as much as 50% of the total taxonomic diversity of Grylloblattodea in Canada is still undocumented. Targeted surveys and taxonomic work, as well as studies that describe the ecology and conservation status of Grylloblattodea are important goals for future research.
-
Conserved and narrow temperature limits in alpine insects: Thermal tolerance and supercooling points of the ice-crawlers, Grylloblatta (Insecta: Grylloblattodea: Grylloblattidae)
Journal of insect physiology, 2015Co-Authors: Sean D. Schoville, Rachel A. Slatyer, James C. Bergdahl, Glenda A. ValdezAbstract:For many terrestrial species, habitat associations and range size are dependent on physiological limits, which in turn may influence large-scale patterns of species diversity. The temperature range experienced by individuals is considered to shape the breadth of the thermal niche, with species occupying temporally and/or geographically stable climates tolerating a narrow temperature range. High-elevation environments experience large temperature fluctuations, with frequent periods below 0 °C, but Grylloblatta (Grylloblattodea: Grylloblattidae) occupy climatically stable microhabitats within this region. Here we test critical thermal limits and supercooling points for five Grylloblatta populations from across a large geographic area, to examine whether the stable microhabitats of this group are associated with a narrow thermal niche and assess their capacity to tolerate cold conditions. Thermal limits are highly conserved in Grylloblatta, despite substantial genetic divergence among populations spanning 1500 m elevation and being separated by over 500 km. Further, Grylloblatta show exceptionally narrow thermal limits compared to other insect taxa with little capacity to improve cold tolerance via plasticity. In contrast, upper thermal limits were significantly depressed by cold acclimation. Grylloblatta maintain coordinated movement until they freeze, and they die upon freezing. Convergence of the critical thermal minima, supercooling point and lower lethal limits point to adaptation to a cold but, importantly, constant thermal environment. These physiological data provide an explanation for the high endemism and patchy distribution of Grylloblatta, which relies on subterranean retreats to accommodate narrow thermal limits. These retreats are currently buffered from temperature fluctuations by snow cover, and a declining snowpack thus places Grylloblatta at risk of exposure to temperatures beyond its tolerance capacity.
-
Ice Crawlers (Grylloblattodea) – the history of the investigation of a highly unusual group of insects
Journal of Insect Biodiversity, 2014Co-Authors: Benjamin Wipfler, Toshiki Uchifune, Romano Dallai, Ryuichiro Machida, Ming Bai, Yingying Cui, Sean D. Schoville, Rolf G BeutelAbstract: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.
-
ice crawlers Grylloblattodea the history of the investigation of a highly unusual group of insects
Journal of Insect Biodiversity, 2014Co-Authors: Benjamin Wipfler, Toshiki Uchifune, Romano Dallai, Ryuichiro Machida, Ming Bai, Yingying Cui, Sean D. Schoville, Rolf G BeutelAbstract: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.
Sven Bradler - One of the best experts on this subject based on the ideXlab platform.
-
The thorax of the cave cricket Troglophilus neglectus: anatomical adaptations in an ancient wingless insect lineage (Orthoptera: Rhaphidophoridae)
BMC Evolutionary Biology, 2016Co-Authors: Fanny Leubner, Thomas Hornschemeyer, Sven BradlerAbstract:Background Secondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive’ group of Ensifera, for which no apomorphic character has been reported so far. Results We present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages. Conclusions Based on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.
-
The thorax of the cave cricket Troglophilus neglectus: anatomical adaptations in an ancient wingless insect lineage (Orthoptera: Rhaphidophoridae)
BMC evolutionary biology, 2016Co-Authors: Fanny Leubner, Thomas Hornschemeyer, Sven BradlerAbstract:Secondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive’ group of Ensifera, for which no apomorphic character has been reported so far. We present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages. Based on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.
Ryuichiro Machida - One of the best experts on this subject based on the ideXlab platform.
-
Comparative transcriptomics of ice-crawlers demonstrates cold specialization constrains niche evolution in a relict lineage.
Evolutionary applications, 2020Co-Authors: Sean D. Schoville, Sabrina Simon, Ryuichiro Machida, Ming Bai, Zachary Beethem, Roman Yu. Dudko, Monika J. B. Eberhard, Paul B. Frandsen, Simon C. Küpper, Max VerheijAbstract:Key changes in ecological niche space are often critical to understanding how lineages diversify during adaptive radiations. However, the converse, or understanding why some lineages are depauperate and relictual, is more challenging, as many factors may constrain niche evolution. In the case of the insect order Grylloblattodea, highly conserved thermal breadth is assumed to be closely tied to their relictual status, but has not been formerly tested. Here, we investigate whether evolutionary constraints in the physiological tolerance of temperature can help explain relictualism in this lineage. Using a comparative transcriptomics approach, we investigate gene expression following acute heat and cold stress across members of Grylloblattodea and their sister group, Mantophasmatodea. We additionally examine patterns of protein evolution, to identify candidate genes of positive selection. We demonstrate that cold specialization in Grylloblattodea has been accompanied by the loss of the inducible heat shock response under both acute heat and cold stress. Additionally, there is widespread evidence of selection on protein-coding genes consistent with evolutionary constraints due to cold specialization. This includes positive selection on genes involved in trehalose transport, metabolic function, mitochondrial function, oxygen reduction, oxidative stress, and protein synthesis. These patterns of molecular adaptation suggest that Grylloblattodea have undergone evolutionary trade-offs to survive in cold habitats and should be considered highly vulnerable to climate change. Finally, our transcriptomic data provide a robust backbone phylogeny for generic relationships within Grylloblattodea and Mantophasmatodea. Major phylogenetic splits in each group relate to arid conditions driving biogeographical patterns, with support for a sister-group relationship between North American Grylloblatta and Altai-Sayan Grylloblattella, and a range disjunction in Namibia splitting major clades within Mantophasmatodea.
-
REVIEW ARTICLE Ice Crawlers (Grylloblattodea) – the history of the investigation of a highly unusual group of insects
2014Co-Authors: Benjamin Wipfler, Toshiki Uchifune, Romano Dallai, Ryuichiro Machida, Ming Bai, Sean Schoville, Yingying CuiAbstract:Abstract: 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 Mantophasmatodea 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
-
Ice Crawlers (Grylloblattodea) – the history of the investigation of a highly unusual group of insects
Journal of Insect Biodiversity, 2014Co-Authors: Benjamin Wipfler, Toshiki Uchifune, Romano Dallai, Ryuichiro Machida, Ming Bai, Yingying Cui, Sean D. Schoville, Rolf G BeutelAbstract: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.
-
ice crawlers Grylloblattodea the history of the investigation of a highly unusual group of insects
Journal of Insect Biodiversity, 2014Co-Authors: Benjamin Wipfler, Toshiki Uchifune, Romano Dallai, Ryuichiro Machida, Ming Bai, Yingying Cui, Sean D. Schoville, Rolf G BeutelAbstract: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.
-
Colliding fragment islands transport independent lineages of endemic rock-crawlers (Grylloblattodea: Grylloblattidae) in the Japanese archipelago.
Molecular phylogenetics and evolution, 2012Co-Authors: Sean D. Schoville, Toshiki Uchifune, Ryuichiro MachidaAbstract:Fragment islands, viewed from the paradigm of island biogeographic theory, depend on continual immigration from continental sources to maintain levels of species diversity, or otherwise undergo a period of relaxation where species diversity declines to a lower equilibrium. Japan is a recently derived fragment island with a rich endemic flora and fauna. These endemic species have been described as paleoendemics, and conversely as recently derived Pleistocene colonists. Geological events in the Miocene period, notably the fragmentation and collision of islands, and the subsequent uplift of mountains in central Japan, provided opportunities for genetic isolation. More recently, cyclical climatic change during the Pliocene and Pleistocene periods led to intermittent land bridge connections to continental Asia. Here we investigate the pattern and timing of diversification in a diverse endemic lineage in order to test whether ongoing migration has sustained species diversity, whether there is evidence of relaxation, and how geological and climatic events are associated with lineage diversification. Using multi-locus genetic data, we test these hypotheses in a poorly dispersing, cold-adapted terrestrial insect lineage (Grylloblattodea: Grylloblattidae) sampled from Japan, Korea, and Russia. In phylogenetic analyses of concatenated data and a species tree approach, we find evidence of three deeply divergent lineages of rock-crawlers in Japan consistent with the pattern of island fragmentation from continental Asia. Tests of lineage diversification rates suggest that relaxation has not occurred and instead endemism has increased in the Japanese Grylloblattidae following mountain-building events in the Miocene. Although the importance of climate change in generating species diversity is a commonly held paradigm in Japanese biogeography, our analyses, including analyses of demographic change and phylogeographic range shifts in putative species, suggests that Pleistocene climatic change has had a limited effect on the diversification of rock-crawlers.
Fanny Leubner - One of the best experts on this subject based on the ideXlab platform.
-
Evolution of the Orthoptera: systematic placement among insects, internal phylogeny and the origin of bioacoustics
2017Co-Authors: Fanny LeubnerAbstract:Die Hauptziele der vorliegenden Arbeit liegen in (1) einer detaillierten morphologischen Studie von Skelett und Muskulatur des Thorax von Orthopteren, (2) einer vergleichenden Studie von verschiedenen Polyneoptera und insbesondere der Ensifera uber die morphologischen Veranderungen im Zusammenhang mit sekundarer Flugellosigkeit, (3) der phylogenetischen Rekonstruktion der Verwandtschaftsverhaltnisse innerhalb der Ensifera basierend auf Merkmalen des thorakalen Skeletts und seiner Muskulatur, (4) einer Neuinterpretation zur Evolution der Bioakustik innerhalb der Ensifera. Die Morphologie des Skeletts und der Muskulatur des Thorax von 23 Arten der Orthoptera wurde im Detail untersucht, wobei reprasentative Vertreter aller wichtigen Taxa der Ensifera einbezogen worden sind. Diese umfangreiche vergleichende Studie diente dabei als Basis fur eine sorgfaltige Rekonstruktion des Grundmusters dieses Merkmalskomplexes fur die Orthoptera. Sowohl die Morphologie des Skeletts als auch die der Muskulatur offenbart zum Teil grose Unterschiede zwischen den beiden Grosgruppen der Orthoptera, den Caelifera (Kurzfuhlerschrecken) und den Ensifera (Langfuhlerschrecken). Die sekundare Flugellosigkeit ist ein weitverbreitetes Phanomen unter den geflugelten Insekten und beeinflusst vor allem die Anatomie des Thorax, insbesondere die des Skeletts und der Muskulatur. Durch den Vergleich der Morphologie des Thorax verschiedener flugelloser Vertreter der Polyneoptera kann gezeigt werden, dass anatomische Anpassungen an die Flugellosigkeit, insbesondere der Flugmuskulatur, innerhalb von Insektentaxa (wie zum Beispiel den Ensifera, Caelifera oder auch Euphasmatodea) sehr einheitlich sind. Allerdings konnen spezifische Anpassungen zwischen diesen einzelnen Linien stark variieren, was auf verschiedenartige Funktionen der verbliebenen Flugmuskeln nach dem Verlust der Flugel hindeutet. Da die systematische Stellung der Orthoptera innerhalb der Polyneoptera derzeit nicht ausreichend geklart ist, wurden neben Vertretern aller Gruppen der Polyneoptera auch reprasentative Arten der Holometabola, Paraneoptera und Palaeoptera in die kladistische Analyse einbezogen. Diese basierte auf der Auswertung von 141 Merkmalen des Thorax und fuhrte zu einer einzigen sparsamsten Verwandtschaftshypothese. Innerhalb der als monophyletisch erkannten Polyneoptera stehen die Orthoptera in einem nahen Verwandtschaftsverhaltnis zu den Xenonomia (Grylloblattodea + Mantophasmatodea), Dictyoptera und Phasmatodea. Die Ensifera zeigen eine basale Aufspaltung in zwei Linien: Grillen und Maulwurfsgrillen (Grylloideen) und Laubheuschrecken sowie ihre Verwandten (Tettigonioideen). Die Tettigoniidae (Laubheuschrecken) bilden das Schwestertaxon zu einem Taxon, dass die Gryllacrididae, Schizodactylidae, Stenopelmatidae, Rhaphidophoridae, Prophalangopsidae und Anostostomatidae umfasst. Die monophyletische Abstammung der letztgenannten Gruppen stutzt sich auf das Vorhandensein eines ausgepragten nach posterior ragenden Profurkalarmes (konvergent bei den Grylloblattodea) und einem paarigen nach hinten gerichteten Fortsatzes der gestielten Prospina (Merkmalsumkehr bei den Prophalangopsidae). Weitere wichtige Ergebnisse zur internen Phylogenie der Ensifera nebst darauf aufbauenden Schlussfolgerungen fur die Evolution der Bioakustik sind im Folgenden kurz aufgefuhrt: (1) Die Prophalangopsidae bilden nicht das Schwestertaxon zu den Tettigoniidae. Die tegminale Stridulation als eine Form der intraspezifischen Kommunikation muss demnach mindestens dreimal unabhangig voneinander entstanden sein: bei den Gryllidae + Gryllotalpidae, Tettigoniidae und Prophalangopsidae. (2) Die Rhaphidophoridae bilden nicht das Schwestertaxon zu den verbleibenden Gruppen der Tettigonioideen. Stattdessen wird eine nahe Verwandtschaft zu den Prophalangopsidae, Anostostomatidae und Stenopelmatidae favorisiert, da alle Vertreter das ihnen eigene Merkmal einer dreigabeligen Metafurca besitzen. Die ursprungliche Hypothese einer basalen Stellung der Rhaphidophoridae innerhalb der Tettigonioideen unterstutzte bislang die Theorie eines tauben und nicht-stridulierenden gemeinsamen Vorfahrens der Ensifera und eine schrittweise verlaufende Evolution ihrer Gehororgane und der damit verbundenen Stridulationsmechanismen hin zu singenden und horenden Vertretern wie beispielsweise den Tettigoniidae. Basierend auf der neuen Verwandtschaftshypothese muss aber davon ausgegangen werden, dass es sich bei der Morphologie der Gehororgane von Rhaphidophoriden, die keine Spuren einer Crista acustica zeigen, um eine sekundare Vereinfachung handelt. (3) Tettigoniidae, Prophalangopsidae und Anostostomatidae bilden keine monophyletische Gruppierung. Das Vorhandensein von akustischer intraspezifischer Kommunikation in diesen drei Taxa, sei es durch tegminale oder femoro-abdominale Stridulation, kann demnach nicht als plesiomorph fur die einzelnen Gruppen interpretiert werden. Vielmehr handelt es sich dabei um unabhangig entstandene apomorphe Merkmale der Tettigoniidae, Prophalangopsidae und einer Teilgruppe der Anostostomatidae. Zusammenfassend liefert diese Arbeit viele zusatzliche Erkenntnisse uber die Morphologie eines vielschichtigen anatomischen Merkmalskomplexes. Die vorliegende Arbeit reprasentiert einen essentiellen Schritt zum tieferen Verstandnis der Evolution von Thoraxmerkmalen und damit assoziierten funktionellen Anpassungen innerhalb der Polyneoptera und insbesondere der Orthoptera. Denn obwohl kladistische Analysen morphologischer Merkmale heutzutage durch solche molekularer Merkmale abgelost werden, bleibt die Morphologie weiterhin ein Wissenschaftszweig, der als wichtigstes Instrument zur Veranschaulichung evolutionarer Prozesse dient, Form und Funktion morphologischer Transformationen erklart und Evolution dadurch greifbar macht.
-
The thorax of the cave cricket Troglophilus neglectus: anatomical adaptations in an ancient wingless insect lineage (Orthoptera: Rhaphidophoridae)
BMC Evolutionary Biology, 2016Co-Authors: Fanny Leubner, Thomas Hornschemeyer, Sven BradlerAbstract:Background Secondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive’ group of Ensifera, for which no apomorphic character has been reported so far. Results We present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages. Conclusions Based on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.
-
The thorax of the cave cricket Troglophilus neglectus: anatomical adaptations in an ancient wingless insect lineage (Orthoptera: Rhaphidophoridae)
BMC evolutionary biology, 2016Co-Authors: Fanny Leubner, Thomas Hornschemeyer, Sven BradlerAbstract:Secondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive’ group of Ensifera, for which no apomorphic character has been reported so far. We present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages. Based on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.
George K. Roderick - One of the best experts on this subject based on the ideXlab platform.
-
RESEARCH ARTICLE Research article
2013Co-Authors: Grylloblatta Species, Sean D. Schoville, George K. RoderickAbstract:Background: Climate in alpine habitats has undergone extreme variation during Pliocene and Pleistocene epochs, resulting in repeated expansion and contraction of alpine glaciers. Many cold-adapted alpine species have responded to these climatic changes with long-distance range shifts. These species typically exhibit shallow genetic differentiation over a large geographical area. In contrast, poorly dispersing organisms often form species complexes within mountain ranges, such as the California endemic ice-crawlers (Grylloblattodea: Grylloblattidae: Grylloblatta). The diversification pattern of poorly dispersing species might provide more information on the localized effects of historical climate change, the importance of particular climatic events, as well as the history of dispersal. Here we use multi-locus genetic data to examine the phylogenetic relationships and geographic pattern of diversification in California Grylloblatta. Results: Our analysis reveals a pattern of deep genetic subdivision among geographically isolated populations of Grylloblatta in California. Alpine populations diverged from low elevation populations and subsequently diversified. Using a Bayesian relaxed clock model and both uncalibrated and calibrated measurements of time to most recent common ancestor, we reconstruct the temporal diversification of alpine Grylloblatta populations. Based on calibrated relaxed clock estimates, evolutionary diversification of Grylloblatta occurred during the Pliocene-Pleistocene epochs
-
Evolutionary diversification of cryophilic Grylloblatta species (Grylloblattodea: Grylloblattidae) in alpine habitats of California.
BMC evolutionary biology, 2010Co-Authors: Sean D. Schoville, George K. RoderickAbstract:Background Climate in alpine habitats has undergone extreme variation during Pliocene and Pleistocene epochs, resulting in repeated expansion and contraction of alpine glaciers. Many cold-adapted alpine species have responded to these climatic changes with long-distance range shifts. These species typically exhibit shallow genetic differentiation over a large geographical area. In contrast, poorly dispersing organisms often form species complexes within mountain ranges, such as the California endemic ice-crawlers (Grylloblattodea: Grylloblattidae: Grylloblatta). The diversification pattern of poorly dispersing species might provide more information on the localized effects of historical climate change, the importance of particular climatic events, as well as the history of dispersal. Here we use multi-locus genetic data to examine the phylogenetic relationships and geographic pattern of diversification in California Grylloblatta.
-
Evolutionary diversification of cryophilic Grylloblattaspecies (Grylloblattodea: Grylloblattidae) in alpine habitats of California
BMC Evolutionary Biology, 2010Co-Authors: Sean D. Schoville, George K. RoderickAbstract:Background Climate in alpine habitats has undergone extreme variation during Pliocene and Pleistocene epochs, resulting in repeated expansion and contraction of alpine glaciers. Many cold-adapted alpine species have responded to these climatic changes with long-distance range shifts. These species typically exhibit shallow genetic differentiation over a large geographical area. In contrast, poorly dispersing organisms often form species complexes within mountain ranges, such as the California endemic ice-crawlers (Grylloblattodea: Grylloblattidae: Grylloblatta ). The diversification pattern of poorly dispersing species might provide more information on the localized effects of historical climate change, the importance of particular climatic events, as well as the history of dispersal. Here we use multi-locus genetic data to examine the phylogenetic relationships and geographic pattern of diversification in California Grylloblatta . Results Our analysis reveals a pattern of deep genetic subdivision among geographically isolated populations of Grylloblatta in California. Alpine populations diverged from low elevation populations and subsequently diversified. Using a Bayesian relaxed clock model and both uncalibrated and calibrated measurements of time to most recent common ancestor, we reconstruct the temporal diversification of alpine Grylloblatta populations. Based on calibrated relaxed clock estimates, evolutionary diversification of Grylloblatta occurred during the Pliocene-Pleistocene epochs, with an initial dispersal into California during the Pliocene and species diversification in alpine clades during the middle Pleistocene epoch. Conclusions Grylloblatta species exhibit a high degree of genetic subdivision in California with well defined geographic structure. Distinct glacial refugia can be inferred within the Sierra Nevada, corresponding to major, glaciated drainage basins. Low elevation populations are sister to alpine populations, suggesting alpine populations may track expanding glacial ice sheets and diversify as a result of multiple glacial advances. Based on relaxed-clock molecular dating, the temporal diversification of Grylloblatta provides evidence for the role of a climate-driven species pump in alpine species during the Pleistocene epoch.
-
evolutionary diversification of cryophilic grylloblatta species Grylloblattodea grylloblattidae in alpine habitats of california
BMC Evolutionary Biology, 2010Co-Authors: Sean D. Schoville, George K. RoderickAbstract:Climate in alpine habitats has undergone extreme variation during Pliocene and Pleistocene epochs, resulting in repeated expansion and contraction of alpine glaciers. Many cold-adapted alpine species have responded to these climatic changes with long-distance range shifts. These species typically exhibit shallow genetic differentiation over a large geographical area. In contrast, poorly dispersing organisms often form species complexes within mountain ranges, such as the California endemic ice-crawlers (Grylloblattodea: Grylloblattidae: Grylloblatta). The diversification pattern of poorly dispersing species might provide more information on the localized effects of historical climate change, the importance of particular climatic events, as well as the history of dispersal. Here we use multi-locus genetic data to examine the phylogenetic relationships and geographic pattern of diversification in California Grylloblatta. Our analysis reveals a pattern of deep genetic subdivision among geographically isolated populations of Grylloblatta in California. Alpine populations diverged from low elevation populations and subsequently diversified. Using a Bayesian relaxed clock model and both uncalibrated and calibrated measurements of time to most recent common ancestor, we reconstruct the temporal diversification of alpine Grylloblatta populations. Based on calibrated relaxed clock estimates, evolutionary diversification of Grylloblatta occurred during the Pliocene-Pleistocene epochs, with an initial dispersal into California during the Pliocene and species diversification in alpine clades during the middle Pleistocene epoch. Grylloblatta species exhibit a high degree of genetic subdivision in California with well defined geographic structure. Distinct glacial refugia can be inferred within the Sierra Nevada, corresponding to major, glaciated drainage basins. Low elevation populations are sister to alpine populations, suggesting alpine populations may track expanding glacial ice sheets and diversify as a result of multiple glacial advances. Based on relaxed-clock molecular dating, the temporal diversification of Grylloblatta provides evidence for the role of a climate-driven species pump in alpine species during the Pleistocene epoch.
