Abstract
AbstractMass extinctions have profoundly influenced the history of life, not only through the death of species but also through changes in ecosystem function and structure. Importantly, these events allow us the opportunity to study ecological dynamics under levels of environmental stress for which there are no recent analogues. Here, we examine the impact and selectivity of the Late Triassic mass extinction event on the functional diversity and functional composition of the global marine ecosystem, and test whether post‐extinction communities in the Early Jurassic represent a regime shift away from pre‐extinction communities in the Late Triassic. Our analyses show that, despite severe taxonomic losses, there is no unequivocal loss of global functional diversity associated with the extinction. Even though no functional groups were lost, the extinction event was, however, highly selective against some modes of life, in particular sessile suspension feeders. Although taxa with heavily calcified skeletons suffered higher extinction than other taxa, lightly calcified taxa also appear to have been selected against. The extinction appears to have invigorated the already ongoing faunal turnover associated with the Mesozoic Marine Revolution. The ecological effects of the Late Triassic mass extinction were preferentially felt in the tropical latitudes, especially amongst reefs, and it took until the Middle Jurassic for reef ecosystems to fully recover to pre‐extinction levels.
Highlights
T H E Late Triassic mass extinction event (LTE), which occurred ~201.6 million years ago (Blackburn et al 2013), is the second biggest biodiversity loss (Alroy 2010) and the third biggest ecological crisis (McGhee et al 2004) since the Cambrian
The same difference between the datasets is evident in functional diversity loss too: seven modes of life apparently disappeared across the LTE according to the occurrence data, whereas five of those modes of life are recorded as being present by the range-through data (Fig. 1B)
As this mode of life is re-occupied by the same order of organisms in the Middle Jurassic, we consider it unlikely that this mode of life was completely vacated at the LTE, and instead infer that the Roveacrinida persisted in abundances that were too low to be recorded in the fossil record, or in areas that have yet to be sampled for Early Jurassic fossils, as observed for Cenozoic occurrences of this group (Gorzelak et al 2011)
Summary
T H E Late Triassic mass extinction event (LTE), which occurred ~201.6 million years ago (Blackburn et al 2013), is the second biggest biodiversity loss (Alroy 2010) and the third biggest ecological crisis (McGhee et al 2004) since the Cambrian. In order to investigate the functional diversity of ecosystems and to study key traits such as feeding, tiering and motility, the ecospace model of Bambach et al (2007) was used to provide a quantitative autecological analysis of all known Middle Triassic to Middle Jurassic marine animal genera This approach has been previously successfully applied to analysis of the Cambrian radiation (Bambach et al 2007), comparisons of Palaeozoic and modern ecosystems (Bush et al 2007; Villeger et al 2011; Knope et al 2015) and studies of both the late Permian (Dineen et al 2014; Foster & Twitchett 2014) and endCretaceous (Aberhan & Kiessling 2015) mass extinction events. The following individual hypotheses were tested: (1) in common with the Late Permian extinction (Foster & Twitchett 2014), despite significant taxonomic losses, the LTE did not result in a reduction in global functional diversity; (2) sessile suspension feeders were selected against, compared to other modes of life across the LTE; (3) heavily calcified organisms were selected against and suffered higher extinction rates than lightly calcified taxa; and (4) taxonomic and functional diversity loss was greater in the tropics than at higher latitudes
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