I
have interests in many aspects of marine paleoecology, including
community change during mass extinctions or intervals of major
environmental change and the general relationship between biodiversity
and relative abundance and ecosystem functioning. Some of my current research projects are outlined below,
but I have a number of other potential topics for interested
students. A complete list of my publications can be viewed here.
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Marine Paleoecology During Late
Paleozoic Climate
Change
Climate change often has
a profound effect on the biosphere. My research has
documented large-scale shifts in the composition of shallow marine
communities in eastern Australia during the transition from the Early
Permian icehouse to the Middle Permian greenhouse. This work
has also shown that cold-adapted taxa of the glacial biota displayed quite disparate responses to climate warming.
Future work will focus on Artinskian communities, integrating
paleoecological data with paleotemperature proxies to determine if
rapid climate fluctuations contributed to disruption of marine
ecosystems.
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 Bivalves Eurydesma and Deltopecten among glacial dropstones, Sakmarian, Maria Island (Tasmania) |
 Silicified Late Permian (Wuchiapingian) brachiopods from the Episkopi Formation, Hydra, Greece |
Permian Extinction Events
My
research on Late Permian extinctions has primarily concentrated on the
earlier end-Guadalupian event, at the end of the Middle Permian. My
data from silicified collections indicate that major changes
in
the abundance of the Paleozoic and Modern faunas predated the
end-Permian extinction event, implying that the extinction was part of
a prolonged environmental crisis. I have also been constructing a large
database of Permian marine invertebrate fossil occurrences, which I
have used to
re-assess the severity and cause of the earlier end-Guadalupian crisis.
My ongoing work seeks to understand the relationship between upwelling
of
euxinic water and the catastrophic deterioration of Permian
ecosystems.
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Decoupling of Diversity and
Abundance
One
of the least understood aspects of paleoecology is the relationship
between taxonomic richness and relative abundance. In general, there
appears to be good correspondence between diversity and abundance at
longer temporal scales and at higher taxonomic levels. Several
instances of decoupling (where richness and abundance are not
correlated) have been recognized, but its prevalence and
causes remain a mystery. My work has documented decoupling of
global diversity and local abundance of brachiopods and molluscs in the
Late Permian; future work will attempt to unravel the causes of that
decoupling. I have also worked in conjunction with other members of the
University of Southern California Paleobiology group to reconstruct
long-term trends in abundance in the Phanerozoic.
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 Diversity and relative abundance of brachiopods, bivalves, and gastropods in the Middle and Late Permian |