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Fossil Biodiversity Distribution as a Habitat Mapping Tool Erin Arnold Antarctic CRC/IASOS
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Introduction Quantifying and qualifying variability in the pelagic ocean, though space and time Exploring biodiversity of Recent fossil planktonic foraminifera: both global distribution and temporal patterns Advantages of foraminifera –Widely distributed, global taxonomy, well preserved in the sedimentary records
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Diversity Indices describe how individuals in a sample are distributed among the species 3 diversity measurements –Species richness (S, simple number of species) –2 diversity indices (Shannon Index, Evenness)
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Diversity Advantages of method: –Species independent –Describe and compare between both ancient and modern systems –Describe and compare between different taxonomic groups
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Spatial Patterns Diversity of fossil forams from coretop records calculated for points distributed over world’s oceans Exploring the response of community structure (dominance and evenness) to habitat change
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Distribution of species number Species Number < 0 0-5 5-10 10-15 15-20 20-25 >25 adapted from Rutherford et al. 1999
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Distribution of Shannon Index <0 0-0.5 0.5-1 1-1.5 1.5-2 2-2.5 >2.5 Shannon Index Arnold 2002
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Distribution of Equitability <0 0-0.2 0.2-0.4 0.4-0.6 0.6-0.8 0.8-1 >1 Arnold 2002
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R=0.335 R=0.500 R=0.618 Species Number Shannon Index Equitability
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Temporal Variability Exploring the temporal variability of the pelagic habitat over a timescale of a half million years Subantarctic Front Polar Front Subtropical Front
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Temporal Variability Rates of change in diversity calculated to determine periods of high variability d Diversity/ d time Absolute values show total magnitude of change The relation between biodiversity and habitat change through time was explored by comparing rates of diversity and oxygen isotope ratios
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Oxygen Isotope Ratios Species Number Shannon Index Equitability
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Conclusions Planktonic habitat sensitive to rapid climate change Rapidly fluctuating diversity during orbitally driven transition periods Diversity is sensitive to habitat, as defined by SST Diversity as a habitat mapping tool can be applied to modern and ancient ecosystems, and to different plankton groups
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