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Competitive displacement among post-Paleozoic cyclostome and cheilostome bryozoans
J J Sepkoski1, F K McKinney, S Lidgard
1Department of Geophysical Sciences, University of Chicago, Illinois 60637, USA.
Paleobiology
|September 7, 2001
Summary
Fossil bryozoans reveal ecological competition. A coupled-logistic model explains diversity changes, showing competitive displacement between cyclostome and cheilostome bryozoans, especially after mass extinctions.
Area of Science:
- Paleontology
- Ecology
- Evolutionary Biology
Background:
- Encrusting bryozoans offer direct fossil evidence of ecological competition at local scales.
- Understanding competitive interactions is key to deciphering macroevolutionary patterns.
Purpose of the Study:
- To investigate the role of interspecific competition in shaping bryozoan diversity through time.
- To test a coupled-logistic model of clade displacement using fossil bryozoan data.
Main Methods:
- Analysis of the macroevolutionary diversity history of cyclostome and cheilostome bryozoans.
- Application of a coupled-logistic model incorporating competitive interactions and mass extinction events.
- Measurement of intrinsic extinction rates from fossil data.
Main Results:
- The coupled-logistic model accurately predicts observed bryozoan diversity history when perturbed by a mass extinction event similar to the Cretaceous/Tertiary boundary.
- Cyclostome bryozoans exhibited low intrinsic extinction rates, leading to slow diversity loss.
- Competitively superior cheilostome bryozoans gradually diversified into the environment, displacing cyclostomes.
Conclusions:
- Microecological evidence of competition aligns with macroevolutionary diversity patterns in post-Paleozoic bryozoans.
- Competition is a significant driver of diversity dynamics in bryozoan clades.
- Mass extinction events play a crucial role in modulating competitive displacement and clade diversity trajectories.
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