RICERCA ITALIANA     

Biotic Evolution and Global Change: selected Late Mesozoic-Early Cenozoic case histories of pelagic ecostystems archived in the Ocean Drilling Program (ODP) and land-section sediments

Università degli Studi di Milano

Abstract

The evolution of life on Earth can be reconstructed using the fossil record and, therefore, paleontology has a key-role in the understanding of the history of our planet. The biosphere continuously interacts with the geosphere, hydrosphere and atmosphere through a complex system of exogenous and endogenous processes operating at short- and long-time scales. A high-priority issue in Earth science is understanding of relationships between biodiversity and global change. Present knowledge of evolutionary processes suggests that biodiversity is probably controlled by changes in the abiotic environment and/or interactions between organisms. While biota reactions to environmental short-term changes are detectable and modelled in extant ecosystems, long-term variations in the biosphere, usually expressed by changes in speciation/extinction rates, turnovers and stability, require investigations of paleobiotic modifications that are preserved only in geological archives.
The links between biotic evolution and environmental pressure are usually derived from compilations of taxonomic diversity in multimillion years time-slices compared with large scale events such as climate and sea level changes. However, this approach gives results strongly biased by the low-resolution sampling of biodiversity unable to detect rapid pulses and turnovers and to precisely date/correlate paleobiological and geological events.
The oceans is the oldest and largest ecosystem on our planet >>>

Principal Investigator

Isabella PREMOLI SILVA Università degli Studi di MILANO

Research Objectives

The primary objective of the proposed research is the reconstruction of evolutionary rates of calcareous nannoplankton and planktonic foraminifers (and calpionellids) in selected case histories in order to test the presumed role of environmental changes on biotic evolution. Being characteriszed by (1) an extraordinary long, complete and detailed record, (2) great abundance , (3) widespread distribution, and (4) sensitivity to short and long-term environmental changes , calcareous plankton is best suited for paleobiological studies and modeling of biosphere-geosphere interactions.
We believe that the traditional approach (diversity curves based on multimillion years sampling) cannot measure in detail evolutionary rates and precisely date/correlate paleobiologic versus geologic events to estimate synchroneity/diachroneity and time lags to derive causal or casual relationships between calcareous plankton evolution and environmental changes. Consequently, our strategy is aimed at the reconstruction of a high-resolution history of both calcareous phytoplankton and zooplankton, focusing, not only on their taxonomic diversity (in terms of species richness and equitability) but also on their distribution and abundance. This approach should eliminate, or al least minimize, biases introduced by multimillion years sampling of biodiversity showing only major diversification and extinction episodes (but shadowing many significant pulses and turnovers) and discrepancies between >>>

Timescale

24 months

National and international background

The Earth is a complex system where endogenous and exogenous processes inexorably interact at short- and long-time scales, leaving traces in the geological archives that geoscientists are trying to decipher. The evolution of life is a crucial piece of the puzzle and paleontology can therefore contribute to unravelling the history of our planet.
Today, a pressing issue in Earth science is to understand interactions between biosphere and geosphere (Knoll 2003) and, in particular, between biodiversity and global change (Culver & Rawson 2000). Biodiversity is determined by (a) changes in the abiotic environment (bottom-up control) and (b) interactions (competition, grazing, predation, viral infections etc.) between organisms (top-down control). Both groups of processes act at short-term ecologic and long-term evolutionary timescales. At the ecologic time-scale, recent works indicate feedbacks and interconnections between the physical, chemical and biologic features of the environment. However, biotic reactions to environmental short-term changes require integration with long-term variations in the biosphere, usually expressed by changes in rates of speciations and extinctions, turnovers and stability.
The search for possibile mechanisms forcing the evolution of life is a major goal of modern paleobiology and the relative importance of biotic vs. abiotic (e.g. environmental) factors triggering speciation/extinction remain elusive.The discussion is epitomized by the >>>