Record of gall abundance as a possible episode of radiation and speciation of galling insects, Triassic, Southern Brazil

Abstract

A possible episode of coevolution between galling insects and plants is reported. It was identified by a high infestation (density) of fossil gall found on the compressed Dicroidium Flora from the Triassic (Ladinian-Carnian) Passo das Tropas Member, Santa Maria Formation, Paraná Basin. The galls were found on phytofossils in 2.2 m thick mudstones with horizontal lamination, intercalated between coarse and medium-grained sandstones with clasts and cross-lamination at the base and top of the section. The associations were identified with a stereomicroscope, after which they were quantified within each botanical group, along with their type, in order to calculate the average number of galls per leaf (density). The overall density found was 4.018. Corystospermales was the predominant botanical group (87.81%), with a gall density of 4.281, followed by Ginkgoales, Equisetales, and Incertae sedis. Current ecological studies indicate that a xerophytic paleoenvironment correlates with high infestations of galling insects. However, many taphonomic, biological, and ecological factors may be involved, resulting in different hypotheses from the same data. On the other hand, they support the interpretations of this record in other aspects discussed. Furthermore, the identified gall density can be interpreted from a paleobiogeographical perspective, showing dispersion at low altitudes and intermediate subtropical latitudes (25º to 38º S or N).

Patterns of insect-mediated damage in a Permian Glossopteris flora from Patagonia (Argentina)

“…Comparisons. Galls have been recorded in Early Pennsylvanian (Beck and Labandeira, 1998) paleofloras from the northern hemisphere; however, in Gondwana, the earliest reports are Permian (McLoughlin, 2011;Cenci and Adami-Rodrigues, 2017). Galls can occur in all plant organs, such as the petiole or lamina of the leaf, or on reproductive structures.…”

Arthropod and Pathogen Damage on Fossil and Modern Plants: Exploring the Origins and Evolution of Herbivory on Land

“…Mesozoic gymnosperm-and fern-dominated plant assemblages typically are characterized by sporadic arthropod and pathogen associations from collections currently of less than 700 specimens that likely represent an inadequate number of samples. Major assemblages (62) include the Middle Triassic of northeastern Italy (71,118); the Middle to Upper Triassic of the Paraná Basin of Brazil (17) and Cuyana Basin of Argentina (79); the Upper Triassic of Arizona, United States (65) and Antarctica (13); and the Middle-Late Jurassic boundary of northeastern China (31,80,90,114). While these assemblages represent a limited number of specimens for definitive conclusions based on quantitative data (101,102), there are two assemblages for which considerable data exist about the composition and structure of arthropod associations of Mesozoic plant communities where gymnosperms are dominant and ferns subdominant-the Late Triassic Aasvoëlberg 411 plant assemblage from the regional Molteno Flora of South Africa (65,67) and the Early Cretaceous Dawangzhangzi plant assemblage of the regional Jehol Flora of northeastern China (31,80,130).…”

Ecology and Evolution of Gall-Inducing Arthropods: The Pattern From the Terrestrial Fossil Record

“…The Cathaysian gall occurs from the latest Triassic Yangcaogou flora from the Yangcaogou Fm of Liaoning Province in Northeastern China, on the broadleaved pinalean Podozamites-Lindleycladus species complex. The gall, DT80, occurs on Podozamites-Lindleycladus leaves as a small, inconspicuous, hemispheroidal gall with a smooth surface (Ding et al, 2015), although these three single, sparse occurrences collectively exhibit a small fraction of the morphological diversity of galls described from the Molteno Fm of the earlier Late Triassic, which apparently experienced a wave of diversification (Cenci and Adami-Rodrigues, 2019).…”