Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction

Abstract

The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician -Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The first (latest Katian) pulse of the LOME preferentially affected genera restricted to deeper waters or to relatively narrow (less than 358) palaeolatitudinal ranges. This pattern is only observed in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions between shifting climate zones and palaeobiogeography may also have been important. We test the latter hypothesis by estimating whether each genus would have been able to track habitats within its thermal tolerance range during the greenhouse -icehouse climate transition. Models including these estimates are favoured over alternative models. We argue that the LOME, long regarded as non-selective, is highly selective along biogeographic and bathymetric axes that are not closely correlated with taxonomic identity.

Graptolite community responses to global climate change and the Late Ordovician mass extinction

“…The species that most strongly declined, in terms of their individual contributions to community composition, were preferentially those adapted to the mesopelagic habitat. Brachiopod species reveal a similar selectivity (18). Extinction of the majority of the graptolite species making up these stressed communities did not occur, however, until the onset of the glacial interval (or even later), when diplograptines were replaced by the neograptine species that migrated into the paleotropics and diversified during the Hirnantian Age.…”

“…The loss of graptolite biodiversity in the LOME, accompanied by the wholesale extinction of the previously dominant Diplograptina (taxonomic use follows ref. 11) and their replacement by the previously marginal, high-latitude Neograptina (12)(13)(14)(15)(16), provides an opportunity to study the impact of climate change on a macroplanktonic invertebrate fauna over several million years during an interval of unusual species turnover (17,18). A focus on climate change over geological timescales as a driver of extinction dynamics leads us to ask whether there is evidence of ecological community changes in the interval leading up to mass extinction.…”

Evolutionary and biogeographical shifts in response to the Late Ordovician mass extinction

“…The results of this phylogeny are then used to reconstruct biogeographical and ecological changes across the evolutionary history of basal strophomenoids to investigate survivorship trends across the extinction event, as well as to determine whether the phylogenetic evidence confirms the latitudinal selectivity proposed by previous taxonomic studies (Finnegan et al . ).…”

“…; Finnegan et al . , ). However, despite the large loss of global biodiversity, the ecological impact of this extinction has been considered minimal, with most families surviving and ecosystems largely returning to similar ecological associations after the event (McGhee et al .…”

Brachiopod faunas after the end Ordovician mass extinction from South China: Testing ecological change through a major taxonomic crisis

“…Recently, Finnegan et al (2016) suggested that the end Ordovician mass extinction was strikingly selective with respect to bathymetric distribution.…”