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Swaby, Emily Jayne
(2024).
DOI: https://doi.org/10.21954/ou.ro.00101626
Abstract
The Toarcian Oceanic Anoxic Event (T-OAE, c.183 Ma) was a period of global warming and associated environmental change, including marine and terrestrial biotic crises. Fossil insect concentrations are documented from European T-OAE strata, however previous studies have focused on the taxonomy of selected specimens.
The first synthesis and description of all known insects (n=370) from Alderton Hill, UK, and an updated record of all insects (n=799) from the coeval Strawberry Bank, UK assemblage, is presented. Statistical analyses show that Strawberry Bank is less diverse and taphonomically biased towards Coleoptera. Ordinal diversity comparisons with extant assemblages from comparable latitudes indicates that Alderton Hill is representative of the Toarcian life assemblage. A new cockroach, Alderblattina simmsi, with the first unequivocal occurrence of anti-predation colouration in cockroaches, is described; suggesting that the T-OAE drove competition and evolutionary change.
To investigate the abundance, diversity and distribution of insects across NW Tethys during the T-OAE, a representative dataset of fossil insects (n = 8572) in museum and institutional collections, derived from the seven European localities with >200 specimens, was compiled. Statistical analyses of this dataset, comprising 22 orders, 104 families, 140 genera and 138 species, reveals high-compositional variation between the localities. Grimmen, Germany, has the highest taxonomic richness, and Strawberry Bank, the lowest. There is a strong positive monotonic correlation between taxonomic diversity and palaeolatitude at all taxonomic levels (Spearman's rs=0.853–0.945), and a weak correlation between diversity and landmass proximity ( rs=0.0771–0.2833); suggesting palaeolatitude was the primary influence on insect abundance and diversity during the T-OAE. Increased Hemipteran abundance is attributed to major continent proximity and its inherent higher habitat heterogeny. The Alderton Hill Hemipteran, Margaroptilon brodiei, signifies endemism.
Additionally, a new damsel-dragonfly, Liassophlebia sp., is described from the Triassic-Jurassic in Somerset, UK, contributing to the knowledge of insect diversity associated with past environmental perturbations.
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