COS 81-1
Species associations of plant and mammal communities from deep time to the recent

Wednesday, August 12, 2015: 1:30 PM
320, Baltimore Convention Center
S. Kathleen Lyons, Department of Paleobiology, University of Nebraska, Lincoln, NE
Kathryn L. Amatangelo, Ecology and Evolutionary Biology, Brown University, Providence, RI
Anna K. Behrensmeyer, Paleobiology, Smithsonian Institution, Washington, DC
Antoine Bercovici, Paleobiology, Smithsonian Institution, Washignton, DC
Jessica L. Blois, School of Natural Sciences, University of California - Merced, Merced, CA
Matthew Davis, Geology and Geophysics, Yale University, New Haven, CT
William DiMichele, Paleobiology, Smithsonian Institution, Washington, DC
Andrew Du, Anthropology, George Washington University, Washington, DC
Jussi Eronen, Geosciences and Geography, University of Helsinki, Helsinki, Finland
J. Tyler Faith, School of Social Science, The University of Queensland, Brisbane, Australia
Gary R. Graves, National Museum of Natural History, Washington, DC
Nathan Jud, Florida Museum of Natural History, University of Florida, Gainsville, FL
Conrad C. Labandeira, National Museum of Natural History, Smithsonian Institution, Washington, D.C.
Cynthia Looy, Integrative Biology, University of California, Berkeley, Berkeley, CA
Brian J. McGill, School of Biology and Ecology / Mitchell Center for Sustainability Solutions/Mitchell Center for Sustainability Solutions, University of Maine, Orono, ME
Joshua Miller, Geology, University of Cincinnati, Cincinnati, OH
David Patterson, Anthropology, George Washington University, Washington, DC
Silvia Pineda-Munoz, Biological Sciences, Macquarie University, Sydney, Australia
Richard Potts, Anthropology, Smithsonian Institution, Washington, DC
Brett R. Riddle, School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV
Rebecca Terry, Integrative Biology, Oregon State University, Corvallis, OR
Anikó Tóth, Paleobiology, Smithsonian Institution, Washington, DC
Werner Ulrich, Animal Ecology, Nicolaus Copernicus Univeristy, Torun, Poland
Amelia Villaseñor, Anthropology, George Washington University, Washington, DC
Jack W. Williams, Geography, University of Wisconsin-Madison, Madison, WI
Scott L. Wing, Paleobiology, National Museum of Natural History - Smithsonian Institution, Washington, DC
Heidi Anderson, Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
John Anderson, Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
Donald Waller, Botany, University of Wisconsin-Madison, Madison, WI
Nicholas J. Gotelli, Biology, University of Vermont, Burlington, VT
Background/Question/Methods

A major focus in contemporary ecology is identifying the patterns and causes of species associations. Recent syntheses have suggested that non-random species pairs in modern communities are dominated by species that are significantly segregated; that is species pairs occur together across communities less frequently than would be expected by chance. This dominance of negative species interactions suggests an important role for processes such as competition, habitat selectivity, dispersal limitation and extinction in structuring modern communities.  The fossil record provides an excellent opportunity to explore the importance of these processes in structuring communities over longer time scales.  Here we analyze the spatial structure of 80 replicated fossil assemblages of plants and animals to reveal the frequencies of aggregated and segregated species pairs and ask whether non-random species associations of plant and mammal assemblages over the last 300 ma are dominated by negative interactions as in the present. We evaluate five possible explanations for our results.  These include the spatial or temporal scale of the data, the taxonomic resolution of the included datasets, the mode of collection of the data, climate variability over time, and the uniqueness of the present. 

Results/Conclusions

Aggregated species pairs dominate from the Carboniferous (307 ma) to the early Holocene (10,000 bp). However, in a Quaternary fossil pollen sequence, and two Quaternary mammal assemblages, there was a progressive shift towards more segregated pairs in recent times. This trend is also consistent with a meta-analysis of 260 contemporary assemblages, which are dominated by segregated species pairs. The pattern cannot be attributed to effects of spatial or temporal grain and extent of sampling, simple taphonomic artifacts, whether it is an island or mainland assemblage, or to increased variability in climate toward the present. Breakpoint analysis indicates that the trend towards fewer positive associations begins approximately 6000 kya, and may point to the increasing influence of anthropogenic effects over the Holocene. These results suggest that the organization of contemporary and Quaternary plant and animal assemblages may differ from those of deeper time slices.

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