ETE Research

We will focus our RCN’s resources and expertise on the following over-arching question: What are the patterns and causal processes of animal and plant community assembly and disassembly over geological time and up to the present-day? Although the group will generate testable hypotheses once meetings get underway, we include examples of initial hypotheses relating to our sub-questions:

1. What are the similarities and differences in organisms that make up communities that persist over time and then disappear (i.e., community assembly and disassembly), across major taxonomic groups (e.g., plants vs. animals, dinosaurs vs. mammals, gymnosperms vs. angiosperms) and different functional groups (e.g., body size, trophic associations, etc.)? Hypothesis: Taxa that co-occur at higher levels of probability than random association are habitat specialists limited by a specific set of resources in their environment (“resource limited habitat trackers”). These organisms persist through time (as chronofaunas or chronofloras) as long as their environmental requirements are met. 
2. How does community assembly/disassembly play out over different spans of time (ecological to geological in scale) and over critical intervals of geological change? Are there different patterns during times of mass vs. background extinctions or protracted intervals of sustained environmental change? Hypothesis: Groups of taxa forming communities are more likely to persist through time if assembled over longer rather than shorter time periods. Likewise, such established communities track periods of sustained environmental change without significant alternation.
3. What is the evidence in the paleobiological record that ecological systems have thresholds or tipping-points beyond which system state changes occur rapidly? Are there positive feedbacks between the physical environment and ecological systems that underlie rapid changes from one kind of ecological organization to another? Hypothesis: Community re-assembly after a perturbation will involve the same group of taxa if the spatial and temporal scale of the perturbation does not exceed a threshold in which environmental resources cannot sustain viable relict populations of these taxa. The spatial and temporal scale of the critical threshold will vary with the type of organism (e.g., plants, large vertebrates, insects) and with the configuration of their ecosystem (overall size, resource patchiness, paleogeographic setting, etc.).
4. Are the relative contributions of processes involved in assembly/disassembly (e.g., speciation, extinction, immigration, emigration) different at different time scales? How do these contributions vary during times when biodiversity is maintained (relative stasis) versus times of accelerated turnover? How is organismic response during intervals of turnover reflected in subsequent recovery time lags? Hypothesis: Immigration and extinction have minimal impact on community structure unless these occur during times of environmental perturbation.
5. Are the relative contributions of processes involved in assembly/disassembly different in pre-human vs. human-dominated landscapes? Hypothesis: Human impact on community assembly and disassembly is similar in pattern to the effects of non-human environmental perturbations that cause community associations to change, but differs in the rate and unpredictability of these perturbations.

We will use a macroecological approach to bridge both evolutionary and ecological theory and theoretical and empirical perspectives. The questions above can only be addressed with a sustained, multi-year approach by an interdisciplinary network that will apply current ecological theory to specific case studies grounded in paleontological field and collections-based research. Through focused discussions among the participants, we will develop a framework of ecological traits (e.g., body size, abundance, functional group, etc.) that characterize plant and animal communities in both modern and fossil data and develop and test new quantitative methods for comparing these ecological traits across different time scales (e.g., geological time, historical time, the present) and across different taxonomic groups. Establishing this “common currency” for ecology and paleoecology will advance both fields by providing the foundation for new understanding of the character, pace, and predictability of community change. Such understanding is relevant to community assembly/disassembly in the past and in the future.

PIs

• Kate Lyons, NMNH - Paleo,
• Kay Behrensmeyer, NMNH - Paleo
• Nicholas Gotelli, University of Vermont

Steering Committee 

• Katie Amatangelo, Brown University
• Jessica Blois, University of California, Merced
• Scott Wing, NMNH - Paleo

Members

• Antoine Bercovici, Lund University
• Rene Bobe, George Washington University
• Bill DiMichele, NMNH - Paleo
• Andrew Du, George Washington University
• Jussi Eronen, University of Helsinki
• Tyler Faith, University of Queensland
• Gary Graves, NMNH - VZ
• Carlos Jaramillo, NMNH - STRI
• Nathan Jud, University of Maryland
• Conrad Labandeira, NMNH - Paleo
• Cindy Looy, University of California Berkeley
• Brian McGill, University of Maine
• David Patterson, George Washington University
• Richard Potts, NMNH - Anthro
• Brett Riddle, University of Nevada, Las Vegas
• Hans Sues, NMNH - Paleo
• Rebecca Terry, Oregon State University
• Anikó Tóth, NMNH - Paleo
• Amelia Villasenor, George Washington University
• Jack Williams, University of Wisconsin, Madison