The four phases of plant-arthropod associations in deep time

Vascular-plant hosts, their arthropod herbivores, and associated functional feeding groups are distributed spatiotemporally into four major herbivore expansions during the past 420 m.y. They are: (1) a Late Silurian to Late Devonian (60 m.y.) phase of myriapod and apterygote, hexapod (perhaps pterygote) herbivores on several clades of primitive vascular-plant hosts and a prototaxalean fungus; (2) a Late Mississippian to end-Permian (85 m.y.) phase of mites and apterygote and basal pterygote herbivores on pteridophyte and basal gymnospermous plant hosts; (3) a Middle Triassic to Recent (245 m.y.) phase of mites, orthopteroids (in the broadest sense) and hemipteroid and basal holometabolan herbivores on pteridophyte and gymnospermous plant hosts; and (4) a mid Early Cretaceous to Recent (115 m.y.) phase of modern-aspect orthopteroids and derived hemipteroid and holometabolous herbivores on angiospermous plant hosts. These host-plant and herbivore associations are mediated by seven functional feeding groups: a) external foliage feeding, b) piercing-and-sucking, c) boring (Phase 1 origins); d) galling, e) seed predation, f) nonfeeding oviposition (Phase 2 origins); and leaf mining (early Phase 3 origin). Within about 20 m.y. of each herbivore expansion, there is a biota that expresses the nearly full spectrum of later plant-arthropod associations. These four associational phases may be linked to the paleoclimatologic variables of greenhouse/icehouse cycles and atmospheric O2 and CO2 levels by uncertain causes, although some relationship probably is present. The 7 functional feeding groups persist through most of the sampled interval but harbor host-plants and arthropod herbivores that are spatiotemporally ephemeral. Poor understanding of associations in Phases 1 to 3 is attributed to disproportionate focus on the angiosperm and holometabolan insect associations of Phase 4

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Obra ressenyada: W. WEITSCHAT and W. WICHARD, Atlas of Plants and Animals in Baltic Amber. Munich: Verlag Dr. Friedrich Pfeil, 2002

The Four Phases of Plant-Arthropod Associations in Deep Time

Vascular-plant hosts, their arthropod herbivores, and associated functional feeding groups are distributed spatiotemporally into four major herbivore expansions during the past 420 m.y. They are: (1) a Late Silurian to Late Devonian (60 m.y.) phase of myriapod and apterygote, hexapod (perhaps pterygote) herbivores on several clades of primitive vascular-plant hosts and a prototaxalean fungus; (2) a Late Mississippian to end-Permian (85 m.y.) phase of mites and apterygote and basal pterygote herbivores on pteridophyte and basal gymnospermous plant hosts; (3) a Middle Triassic to Recent (245 m.y.) phase of mites, orthopteroids (in the broadest sense) and hemipteroid and basal holometabolan herbivores on pteridophyte and gymnospermous plant hosts; and (4) a mid Early Cretaceous to Recent (115 m.y.) phase of modern-aspect orthopteroids and derived hemipteroid and holometabolous herbivores on angiospermous plant hosts. These host-plant and herbivore associations are mediated by seven functional feeding groups: a) external foliage feeding, b) piercing-and-sucking, c) boring (Phase 1 origins); d) galling, e) seed predation, f) nonfeeding oviposition (Phase 2 origins); and leaf mining (early Phase 3 origin). Within about 20 m.y. of each herbivore expansion, there is a biota that expresses the nearly full spectrum of later plant-arthropod associations. These four associational phases may be linked to the paleoclimatologic variables of greenhouse/icehouse cycles and atmospheric O2 and CO2 levels by uncertain causes, although some relationship probably is present. The 7 functional feeding groups persist through most of the sampled interval but harbor host-plants and arthropod herbivores that are spatiotemporally ephemeral. Poor understanding of associations in Phases 1 to 3 is attributed to disproportionate focus on the angiosperm and holometabolan insect associations of Phase 4

A \u3cem\u3eDendroctonus\u3c/em\u3e Bark Engraving (Coleoptera: Scolytidae) From A Middle Eocene \u3cem\u3eLarix\u3c/em\u3e (Coniferales: Pinaceae): Early Or Delayed Colonization?

An engraving made by a scolytid bark beetle, assigned to the genus Dendroctonus of the tribe Tomicini, has been identified on a mummified, middle Eocene (45 Ma) specimen of Larix altoborealis wood from the Canadian High Arctic. Larix altoborealis is the earliest known species of Larix, a distinctive lineage of pinaceous conifers that is taxonomically identifiable by the middle Eocene and achieved a broad continental distribution in northern North America and Eurasia during the late Cenozoic. Dendroctonus currently consists of three highly host-specific lineages that have pinaceous hosts: a basal monospecific clade on Pinoideae (Pinus) and two sister clades that consist of a speciose clade associated exclusively with Pinoideae and six species that breed overwhelmingly in Piceoideae (Picea) and Laricoideae (Pseudotsuga and Larix). The middle Eocene engraving in L. altoborealis represents an early member of Dendroctonus that is ancestral to other congeneric species that colonized a short-bracted species of Larix. This fossil occurrence, buttressed by recent data on the phylogeny of Pinaceae subfamilies and Dendroctonus species, indicates that there was phylogenetically congruent colonization by these bark-beetle lineages of a Pinoideae + (Piceoideae + Laricoideae) host-plant sequence. Based on all available evidence, an hypothesis of a geochronologically early invasion during the Early Cretaceous is supported over an alternative view of late Cenozoic cladogenesis by bark beetles onto the Pinaceae. These data also suggest that host-plant chemistry may be an effective species barrier to colonization by some bark-beetle taxa over geologically long time scales

Sampling fossil floras for the study of insect herbivory: how many leaves is enough?

Despite the great importance of plant–insect interactions to the functioning of terrestrial ecosystems, many temporal gaps exist in our knowledge of insect herbivory in deep time. Subsampling of fossil leaves, and subsequent extrapolation of results to the entire flora from which they came, is practiced inconsistently and according to inconsistent, often arbitrary criteria. Here we compare herbivory data from three exhaustively sampled fossil floras to establish guidelines for subsampling in future studies. The impact of various subsampling routines is evaluated for three of the most common metrics of insect herbivory: damage type diversity, nonmetric multidimensional scaling, and the herbivory index. The findings presented here suggest that a minimum fragment size threshold of 1&thinsp;cm2 always yields accurate results and that a higher threshold of 2&thinsp;cm2 should yield accurate results for plant hosts that are not polyphyletic form taxa. Due to the structural variability of the plant hosts examined here, no other a priori subsampling strategy yields consistently accurate results. The best approach may be a sequential sampling routine in which sampling continues until the 100 most recently sampled leaves have caused no change to the mean value or confidence interval for damage type diversity and have caused minimal or no change to the herbivory index. For nonmetric multidimensional scaling, at least 1000&thinsp;cm2 of leaf surface area should be examined and prediction intervals should be generated to verify the relative positions of all points. Future studies should evaluate the impact of subsampling routines on floras that are collected based on different criteria, such as angiosperm floras for which the only specimens collected are those that are at least 50&thinsp;% complete.</p

Life habits, hox genes, and affinities of a 311 million-year-old holometabolan larva

Citation: Haug, J. T., Labandeira, C. C., Santiago-Blay, J. A., Haug, C., & Brown, S. (2015). Life habits, hox genes, and affinities of a 311 million-year-old holometabolan larva. Bmc Evolutionary Biology, 15, 10. doi:10.1186/s12862-015-0428-8Background: Holometabolous insects are the most diverse, speciose and ubiquitous group of multicellular organisms in terrestrial and freshwater ecosystems. The enormous evolutionary and ecological success of Holometabola has been attributed to their unique postembryonic life phases in which nonreproductive and wingless larvae differ significantly in morphology and life habits from their reproductive and mostly winged adults, separated by a resting stage, the pupa. Little is known of the evolutionary developmental mechanisms that produced the holometabolous larval condition and their Paleozoic origin based on fossils and phylogeny. Results: We provide a detailed anatomic description of a 311 million-year-old specimen, the oldest known holometabolous larva, from the Mazon Creek deposits of Illinois, U.S.A. The head is ovoidal, downwardly oriented, broadly attached to the anterior thorax, and bears possible simple eyes and antennae with insertions encircled by molting sutures; other sutures are present but often indistinct. Mouthparts are generalized, consisting of five recognizable segments: a clypeo-labral complex, mandibles, possible hypopharynx, a maxilla bearing indistinct palp-like appendages, and labium. Distinctive mandibles are robust, triangular, and dicondylic. The thorax is delineated into three, nonoverlapping regions of distinctive surface texture, each with legs of seven elements, the terminal-most bearing paired claws. The abdomen has ten segments deployed in register with overlapping tergites; the penultimate segment bears a paired, cercus-like structure. The anterior eight segments bear clawless leglets more diminutive than the thoracic legs in length and cross-sectional diameter, and inserted more ventrolaterally than ventrally on the abdominal sidewall. Conclusions: Srokalarva berthei occurred in an evolutionary developmental context likely responsible for the early macroevolutionary success of holometabolous insects. Srokalarva berthei bore head and prothoracic structures, leglet series on successive abdominal segments - in addition to comparable features on a second taxon eight million-years-younger - that indicates Hox-gene regulation of segmental and appendage patterning among earliest Holometabola. Srokalarva berthei body features suggest a caterpillar-like body plan and head structures indicating herbivory consistent with known, contemporaneous insect feeding damage on seed plants. Taxonomic resolution places Srokalarva berthei as an extinct lineage, apparently possessing features closer to neuropteroid than other holometabolous lineages

Life habits, hox genes, and affinities of a 311 million-year-old holometabolan larva

Background: Holometabolous insects are the most diverse, speciose and ubiquitous group of multicellular organisms in terrestrial and freshwater ecosystems. The enormous evolutionary and ecological success of Holometabola has been attributed to their unique postembryonic life phases in which nonreproductive and wingless larvae differ significantly in morphology and life habits from their reproductive and mostly winged adults, separated by a resting stage, the pupa. Little is known of the evolutionary developmental mechanisms that produced the holometabolous larval condition and their Paleozoic origin based on fossils and phylogeny. Results: We provide a detailed anatomic description of a 311 million-year-old specimen, the oldest known holometabolous larva, from the Mazon Creek deposits of Illinois, U.S.A. The head is ovoidal, downwardly oriented, broadly attached to the anterior thorax, and bears possible simple eyes and antennae with insertions encircled by molting sutures;other sutures are present but often indistinct. Mouthparts are generalized, consisting of five recognizable segments: a clypeo-labral complex, mandibles, possible hypopharynx, a maxilla bearing indistinct palp-like appendages, and labium. Distinctive mandibles are robust, triangular, and dicondylic. The thorax is delineated into three, nonoverlapping regions of distinctive surface texture, each with legs of seven elements, the terminal-most bearing paired claws. The abdomen has ten segments deployed in register with overlapping tergites;the penultimate segment bears a paired, cercus-like structure. The anterior eight segments bear clawless leglets more diminutive than the thoracic legs in length and cross-sectional diameter, and inserted more ventrolaterally than ventrally on the abdominal sidewall. Conclusions: Srokalarva berthei occurred in an evolutionary developmental context likely responsible for the early macroevolutionary success of holometabolous insects. Srokalarva berthei bore head and prothoracic structures, leglet series on successive abdominal segments - in addition to comparable features on a second taxon eight million-years-younger - that indicates Hox-gene regulation of segmental and appendage patterning among earliest Holometabola. Srokalarva berthei body features suggest a caterpillar-like body plan and head structures indicating herbivory consistent with known, contemporaneous insect feeding damage on seed plants. Taxonomic resolution places Srokalarva berthei as an extinct lineage, apparently possessing features closer to neuropteroid than other holometabolous lineages

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

Insects are a highly diverse group of organisms and constitute more than half of all known animal species. They have evolved an extraordinary range of traits, from flight and complete metamorphosis to complex polyphenisms and advanced eusociality. Although the rich insect fossil record has helped to chart the appearance of many phenotypic innovations, data are scarce for a number of key periods. One such period is that following the End-Permian Extinction, recognized as the most catastrophic of all extinction events. We recently discovered several 240-million-year-old insect fossils in the Mount San Giorgio Lagerstatte (Switzerland-Italy) that are remarkable for their state of preservation (including internal organs and soft tissues), and because they extend the records of their respective taxa by up to 200 million years. By using these fossils as calibrations in a phylogenomic dating analysis, we present a revised time scale for insect evolution. Our date estimates for several major lineages, including the hyperdiverse crown groups of Lepidoptera, Hemiptera: Heteroptera and Diptera, are substantially older than their currently accepted post-Permian origins. We found that major evolutionary innovations, including flight and metamorphosis, appeared considerably earlier than previously thought. These results have numerous implications for understanding the evolution of insects and their resilience in the face of extreme events such as the End-Permian Extinction

The fossil record and taphonomy of butterflies and moths (Insecta, Lepidoptera): implications for evolutionary diversity and divergence-time estimates

It is conventionally accepted that the lepidopteran fossil record is significantly incomplete when compared to the fossil records of other, very diverse, extant insect orders. Such an assumption, however, has been based on cumulative diversity data rather than using alternative statistical approaches from actual specimen counts. We reviewed documented specimens of the lepidopteran fossil record, currently consisting of 4,593 known specimens that are comprised of 4,262 body fossils and 331 trace fossils. The temporal distribution of the lepidopteran fossil record shows significant bias towards the late Paleocene to middle Eocene time interval. Lepidopteran fossils also record major shifts in preservational style and number of represented localities at the Mesozoic stage and Cenozoic epoch level of temporal resolution. Only 985 of the total known fossil specimens (21.4%) were assigned to 23 of the 40 extant lepidopteran superfamilies. Absolute numbers and proportions of preservation types for identified fossils varied significantly across superfamilies. The secular increase of lepidopteran family-level diversity through geologic time significantly deviates from the general pattern of other hyperdiverse, ordinal-level lineages. Our statistical analyses of the lepidopteran fossil record show extreme biases in preservation type, age, and taxonomic composition. We highlight the scarcity of identified lepidopteran fossils and provide a correspondence between the latest lepidopteran divergence-time estimates and relevant fossil occurrences at the superfamily level. These findings provide caution in interpreting the lepidopteran fossil record through the modeling of evolutionary diversification and in determination of divergence time estimates.https://doi.org/10.1186/s12862-015-0290-

A specialized feeding habit of early permian oribatid mites

© 2014 Elsevier B.V. Oribatid mites (Acari: Oribatida) are very diverse and important detritivorous and fungivorous micro-arthropods in modern forest ecosystems. Although the fossil record of oribatid mites can be traced to the Early Devonian, the paleoecology of oribatid mites during the deep geological past remains poorly understood. Remarkably good preservation of tunnel networks in a permineralized conifer wood specimen is described from the Early Permian of Germany. This fossil provides evidence for four aspects of oribatid mite feeding habits. First, there is preferred consumption of the more indurated tissues from growth-ring cycles. Second, tracheids were targeted for consumption. Third, feeding on tissues resulted in fecal pellet accumulations at the bottoms of tunnels. And fourth, the absence of feeding on ambient decomposing fungi such as necroses and rots, but rather the processing of pristine plant tissues, indicate the presence of a self-contained, microorganismic gut biota. These rather specialized feeding habits allowed oribatid mites a prominent role in the decomposition of digestively refractory plant tissues in Early Permian ecosystems