RICERCA ITALIANA     

Calcareous plankton evolutionary accelerations and their relationships to global changes during the Mesozoic and Cenozoic. Do global changes matter or not?

Università degli Studi di Milano

Abstract

Recent environmental change and climate instability pose urgent questions regarding biota ability to keep pace with concurrent excess CO2 and global warming. Major concerns are addressed to the possibility that biodiversity loss derives from biota inability of sustaining rapid and progressive environmental changes accelerated by anthropogenic emissions of greenhouse gases. However, the findings of “new” organisms in various ecosystems raise the possibility that global change might stimulate biota speciation and/or innovation. New life forms might represent temporary adaptation to environmental stress or be real new species evolved in response to global change.
The ocean is the oldest and largest ecosystem on Earth and best records global changes in climate and atmospheric composition, as well as endogenous processes inducing major variations in physical, chemical and trophic parameters. Within the biosphere, calcareous plankton play a special role, as nannoplankton and planktonic foraminifers are the most effective calcite producers of the planet since the Jurassic. They are widespread, represented by both cosmopolitan and endemic taxa, relevant for both the inorganic and organic carbon cycle, are extremely sensitive to environmental variations and may direct climate change by altering albedo and absorption/emission of CO2 at large scale.
The Phanerozic geological record of global change unambiguously indicates that the Earth system already experienced >>>

Principal Investigator

Isabella Premoli Silva Università degli Studi di MILANO

Research Objectives

The history of calcareous plankton indicates that times of accelerated rates of radiations/extinctions correlate with global changes in the geosphere, hydrosphere and atmosphere suggesting that evolutionary patterns are intimately linked to environmental modifications. The primary objective of the proposed research is to reconstruct evolutionary rates of calcareous nannoplankton, planktonic foraminifers and calpionellids in selected case histories in order to test the presumed role of environmental pressure on biotic evolution.
We aim at contributing to the major issue of recent global changes (rapid CO2 increase and warming, climate instability) impacting ecosystems. Specifically, by investigating geological examples of extreme environmental changes we plan to decipher reactions and adaptations of the biosphere for supplying more realistic predictions of future ecosystem functioning. Phanerozic sedimentary successions preserve records of global change to (super)greenhouse and (super)icehouse states. We selected case histories represented by pelagic, well-dated successions from at least 2 different oceans, with occurrence of abundant and well-preserved nannofossil and planktonic foraminiferal assemblages and significant variations in evolutionary rates of both planktonic groups. This criteria ensure to obtain a supraregional to global picture of biotic evolutionary patterns with highest temporal resolution for the ocean, the oldest and largest ecosystem on Earth.
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First Results

Major uncertainties about the long-range predictions of the impacts of global change weaken the short-term (decadal) projections of biodiversity relative to climate scenarios assessing high extinction risk in the near future. Our proposed research is expected to contribute to the understanding of the relationships among environmental change and ecosystem functioning. Biodiversity is determined by changes in abiotic factors and interactions (competition, grazing, predation, viral infections etc.) between organisms. 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. Biotic reactions to short-term environmental 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 (environmental) factors triggering speciation/extinction remain elusive. In this context, highly-resolved analyses of the evolutionary events are necessary to shed light on the relative timing between abiotic factors (environmental changes) and biota evolution.
Major concerns are addressed to the possibility of near future extinctions depauperating the >>>

Timescale

24 months

National and international background

Life is a crucial piece of the Earth system where processes interact at short- and long-time scales, leaving fingerprints that geoscientists are trying to decipher. A major issue of present global changes regards the impact of rapid warming and climate instability on ecosystems. Increasing concern is addressed to the biosphere capability to react and adapt to accelerate environmental changes. The ability of species to reach new climatically suitable areas will be hampered by habitat loss and fragmentation, and their skill to persist in appropriate climates may be affected by new invasive organisms.
Climate change over the past 30 years has produced shifts in biota abundance, distribution and extinction (Pounds et al 1999; Parmesan & Yohe 2003). Comparative studies have revealed the extent to which functional substitutions alter ecosystem properties such as productivity and resistance/resilience to perturbations. The responsiveness of biota to recent environmental change raises the possibility that anthropogenic climate change could be the major cause of extinction in the near future. The prediction of ecosystem responses to global change requires full understanding of complex processing operating at short- and long-term scales. Short-term (decadal) projection of biodiversity relative to climate scenarios assess high extinction risk: the near future greenhouse state has been predicted to force 18% to 35% of species to become extinct (Thomas et al 2005). For >>>