Effects of environmental perturbation during the Late Triassic on the taxic diversity of British insects

Abstract

The Late Triassic is a time of interest for investigating past periods of environmental perturbation as it experienced one of the most devasting extinction events in Earth history, the end Triassic extinction. Examining such past events is useful for understanding the broad patterns of ecosystem dynamics and how they respond to environmental change through time. Insects are incredibly diverse and integral to almost all terrestrial ecosystems. Therefore, understanding the dynamics of insect diversity and ecology through time provides insights into the processes that shape terrestrial ecosystems. A dataset of insect occurrence through the Triassic/Jurassic boundary (TJB) was compiled to analyse diversity dynamics and detect an extinction signal. Most insects from the Rhaetian/Hettangian were collected from the Severn Valley in Southwest England. From an initial assessment two main issues were found, namely, a lack of current discussion on the age of the insect-bearing deposits and the poor taxonomic state of the insects. Through stratigraphic revision, a series of insect-bearing horizons was established through the TJB. Then, the ~4000 British insect fossils were identified, dubious historical taxonomy was revised (nine species removed as nomen dubia), and newly discovered taxa were described (one new family, six new genera, and 16 new species). The compositions of the Rhaetian–Sinemurian assemblages were assessed in terms of species- and genus-level diversity and ecology. The results suggest that these assemblages are indeed distinct and do record a dramatic disruption to insect diversity in the Hettangian. However, the UK data are too patchy to establish long-term trends, so they were included in a dataset of all insects from the Late Triassic/Early Jurassic from the Palaeobiology Database. Through a series of analyses at a range of geographic, stratigraphic, and taxonomic levels compelling evidence was found for a dramatic decline in insect diversity at both local and global scales.

Date of Award	19 Mar 2019
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Michael J Benton (Supervisor) & Andrew Ross (Supervisor)