TRIASDIVERSITY · Patterns and processes of species diversification after mass extinctions: A case study on Triassic Pectinoidea (Mollusca, Bivalvia)
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2006-01-01 → 2007-12-31
- EU contribution
- €168,233
- Participants
- 1
- Scheme
- SCF
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Results in brief
Final Activity Report Summary - TRIASDIVERSITY (Patterns and processes of species diversification after mass extinctions: A case study on Triassic Pectinoidea (Mollusca, Bivalvia))
Understanding how life diversified in the geological past is a key to predict future changes in biosphere. In order to reveal general insight into the controls of global biodiversification, we reconstructed global species diversification of pectinoid bivalves ('scallops') during the Triassic period (250-200 million years before present), which followed the greatest mass extinction event in Earth's history. We found that the number of pectinoid species increased exponentially during the initial 35 million years after the extinction event, which suggests that global diversity was not damped by competition for a considerable period of geological time. Rather, the exponential diversity increase supports a prediction of so-called expansion models of biodiversification, which emphasise the positive role of biotic interaction on the number of niches and hence the number of species that an ecosystem carries. However, the number of pectinoid species within habitats (alpha diversity) showed a much shorter increase (ca. 6 million years) and then remained more or less constant until the end of the period. This is a prediction of equilibrium models of biodiversification, which postulate the prevalence of competition in the biotic interaction between organisms, posing limits on carrying capacity of ecosystems. The contrasting pattern of global and alpha diversity in the Triassic expansion of pectinoid bivalves suggests that equilibrium models of biodiversification might explain diversity patterns at the level of local ecosystems but can probably not be projected to the global scale. Here, differentiation between habitats (beta diversity) and biogeographical regions (gamma diversity) plays a key role, on which competition between groups with similar ecological demands has little effect. Towards the end of the Triassic period, the number of known pectinoid species declined, which probably reflects the combined effect of a poorer fossil record and worsening environmental conditions that finally culminated in the end-Triassic mass extinction event.
Data: CORDIS, © European Union
Project objective
A comprehensive survey of all Triassic pectinoid bivalves (`scallops) will allow for the first time an analysis of patterns and processes of global biodiversification at the species level. Triassic pectinoids are particularly suitable to reveal general ins ights into biodiversification processes, because the end-Permian mass extinction event left members of this superfamily nearly unaffected, whereas their most important competitors (brachiopods) suffered dramatically. This unique historical background allow s us to study how global diversification of a major group of marine invertebrates proceeded in the virtual absence of competition, and how (re)establishment of interacting groups influenced the diversification patterns and processes later. For this purpose , species diversity plots of Triassic pectinoids will be constructed and corrected for rock volume and sampling bias. Exponential and logistic curves will then be fitted to these plots and analysed in terms of their statistical significance and biological meaning. Overall shape of the diversity curves and the nature of their best fits (i.e., logistic or exponential) will be used to test rival concepts of biodiversification including underlying assumptions about the relative importance of competition, predat ion, positive biotic interaction, newly evolved adaptations, and intrinsic rates of diversification and equilibrium diversities. A crucial question particularly in testing equilibrium versus non-equilibrium models will be whether the end-Permian extinction event was followed by initial hyperexponential bursts into the largely vacated ecosystems, or rather by slowly accelerating biodiversification, indicating a central role for positive feedback processes. The results obtained for Triassic pectinoids are exp ected to be paradigmatic for marine biodiversification in general, and will significantly advance the development of data-based concepts of biodiversification.
Original text from CORDIS.
Participants
- UNIVERSITY OF BRISTOL · BRISTOL, CLIFTONCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union