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| Reconstruction of the parasitic relationship between the insect-induced gall Paleogallus carpannularites ichnosp. nov. and its calamitalean host plant Annularia paisii sp. nov.
Correia, Bashforth, Šimůnek, et al. 2020.
DOI: 10.1086/707105
Artwork: Andrey Atuchin
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Abstract
Premise of research. Sphenophytes are a modestly diverse lineage of vascular plants with a persistent record extending from the late Paleozoic to the present. However, patterns of arthropod herbivory on sphenophytes are poorly known because of a scattered literature, which we address in this report.
Methodology. We document the 315-million-year-long record of sphenophyte-arthropod herbivory by focusing on the bookends of that record—namely, the Pennsylvanian and the present day. We add to this milieu a gall association on a newly described sphenophyte from the Upper Pennsylvanian of Portugal.
Pivotal results. Earliest-known sphenophyte herbivory is Early Pennsylvanian, when virtually all interactions involved piercing-and-sucking damage by stylate insect mouthparts and lesions from cutting-and-slicing ovipositors. An exception is a newly discovered calamitalean (Annularia paisii sp. nov.) that harbored a newly discovered insect-induced gall (Paleogallus carpannularites ichnosp. nov.) that is similar to a modern fern gall. This discovery suggests that Late Pennsylvanian interactions were more diverse than previously suspected. By the end of the Pennsylvanian, the component community of one whole-plant calamitalean species had 12 damage types (DTs), only one of which was nonpuncturing damage. Shifts to external foliage feeding, mining, and galling are evident during the Late Triassic. A Middle Jurassic renewal of interactions was followed by a decrease in documented DTs present in the Cretaceous and Cenozoic. Fifteen modern species of the genus Equisetum, the sole surviving sphenophyte lineage, exhibit four herbivory patterns. First, almost all documented herbivory is confined to the seven species of Equisetum (horsetails), not subgenus Hippochaete (scouring rushes). Second, there are diversification events of four genera of herbivores—a beetle, two sawflies, and a fly—on subgenus Equisetum. Third, this arthropod herbivory is approximately evenly split among monophagy, oligophagy, and polyphagy. Fourth, the herbivore component community of Equisetum arvense L. (field horsetail) is diverse, representing 10 major feeding modes, comparable to a modern angiosperm species; there are considerably more feeding modes for E. arvense than there are for Pennsylvanian calamitaleans.
Conclusions. Pennsylvanian sphenophytes supported few folivores, and there was a major shift in the modes of sphenophyte herbivory after the Paleozoic. Considerable modern herbivory is localized on E. arvense.
Keywords: Annularia, arthropods, Equisetales, galls, Gzhelian, plant-insect interactions.
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| Fig. 5 Photographic documentation of Annularia paisii sp. nov. (holotype UP-MHNFCP155167), from the São Pedro da Cova region, Douro Carboniferous Basin (DCB), northwestern Portugal. A, The entire specimen. B, A branchlet of the central-left area in (A), showing whorls of foliage along a lateral branch immediately distal to the insect-induced gall. C, Enlargement of the gall Paleogallus carpannularites ichnosp. nov. and surrounding area, showing details of its attachment to the node. |
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| Fig. 3 An interpretative view drawing of the holotype specimen of Annularia paisii sp. nov. and Paleogallus carpannularites ichnosp. nov. (UP-MHNFCP-155167). A, The entire specimen. B, Selected branch, showing configuration of stem, sheathed node and gall. C, Insect-induced gall (Paleogallus carpannularites ichnosp. nov.) on Annularia paisii sp. nov. in grey, showing its relationship to the node, branch and stem of the host plant. |
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| Fig. 6 Annularia paisii sp. nov. (paratype UP-MHNFCP-155168), from the São Pedro da Cova region, Douro Carboniferous Basin, northwestern Portugal. A, Four individual branches bearing whorls of leaves at nodes. B, Enlargement of branch at left in (A). C, Enlargement of branch at right in (A). D, Enlargement of rectangular box above in (A), showing elongate leaves with a strong medial vein and acuminate tips. E, Enlargement of rectangular box above in (B), displaying the approximately 7–9 leaves per node. F, Detail of foliage from the rectangular box in (C), displaying individual curved-lanceolate leaves with a prominent medial vein and acuminate tips. |
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| Fig. 8 Structure of the insect-induced gall Paleogallus carpannularites ichnosp. nov. and its attachment to host Annularia paisii sp. nov. A, Detail of the gall outer wall, showing outer surface of inner nutritive tissue through an exfoliated area, and thin outer gall wall, perhaps resulting from extensive taphonomic compression. B, Another view of the gall, oriented 180° to that in (A). C, Magnification of gall in (B), revealing details of the striae and pustules on the gall surface.
Scale bars = 3 mm; abbreviations: branch, br; leaf, lf; node, no; pedicel, pe; gall surface, gs; coalified matter, cm.
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Fig. 4 Reconstruction of the parasitic relationship between the insect-induced gall Paleogallus carpannularites ichnosp. nov. and its calamitalean host plant Annularia paisii sp. nov. This reconstruction was drawn by scientific illustrator Audrey Atuchin, based on line drawing of holotype specimen and supplementary pictures provided by P. Correia. |
Pedro Correia, Arden R. Bashforth, Zbynĕk Šimůnek, Christopher J. Cleal, Artur A. Sá and Conrad C. Labandeira. 2020. The History of Herbivory on Sphenophytes: A New Calamitalean with an Insect Gall from the Upper Pennsylvanian of Portugal and a Review of Arthropod Herbivory on an Ancient Lineage. International Journal of Plant Sciences. DOI: 10.1086/707105
New species of ancient horsetail reveals relationship between plants, parasitoid insects about 300 million years ago sciencex.com/news/2020-04-species-ancient-horsetail-gall-reveals.html via @sciencex_com
