Outline

Echo is a simulation tool developed to investigate mechanisms which regulate diversity and information-processing in systems comprised of many interacting adaptive agents, or complex adaptive systems (CAS). Echo agents interact via combat, trade and mating and develop strategies to ensure survival in resource-limited environments. Individual genotypes encode rules for interactions. In a typical simulation, populations of these genomes evolve interaction networks which regulate the flow of resources. Resulting networks resemble species communities in ecological systems. Flexibly defined parameters and initial conditions enable researchers to conduct a range of "what-if" experiments.

This figure illustrates the hierarchical organization of the Echo world. Resources, which are represented as letters (a,b,c,d), constitute the agents' genomes. Agents can forage for resources, interact with one another, and self-reproduce when they have sufficient resources to copy their genome, all within a particular site. A site is analogous to a chemostat; a world is comprised of one or more sites. Agents migrate among sites when they cannot find resources.

If you would like to run a Java version of Echo by Hans Woppman, visit here.

More detailed descriptions are available in Refs. 1-4.

Please note that this implementation is not now being maintained. Further, no graphical user interface is available for the current version. However, many options to log variables at specified intervals have been provided.

Please do not send us mail asking how to compile earlier Echo versions. The widgets will not compile and earlier versions are not being supported.

The current version is 1.3 beta 2. The existing implementation of Echo runs on most UNIX and LINUX systems. Click here to ftp the tarred, compressed distribution.

Terry Jones wrote a document to describe how to use this implementation. It details how to compile and install the C source code, and walks the user through an example run. Unfortunately, it is a bit outdated and only describes version 1.1. Click here to ftp the compressed postscript file [Ref. 4], or click here to view the HTML version.

Ginger Booth and Oswald Schmitz revised Echo to study trophic cascades in a three species (tritrophic) food web. Their implementation is called Gecko. Click here to learn more about Gecko.

• Forrest, S. and T. Jones. 1994. Modeling complex adaptive systems with Echo. pp. 3-21 in R.J. Stonier and X.H. Yu, eds. Complex Systems: Mechanisms of Adaptation. IOS Press, Amsterdam. (Click here to download the gzipped postscript file.)
  
  
• Schmitz, O.J. and G. Booth. 1996. Modeling food web complexity: The consequence of individual-based spatially explicit behavioral ecology on trophic interactions. Evolutionary Ecology 11:379-398. (Click here to view the HTML version of their paper.)
  
  
• Hraber, P.T., T. Jones and S. Forrest. 1997. The ecology of Echo. Artificial Life 3(3):165-190. (Click here for the pdf file.)
  
  
• Hraber, P.T. and B.T. Milne. 1997. Community Assembly in a Model Ecosystem. Ecological Modelling 103:267-285. (Click here for a gzipped postscript file or here to view the abstract.)

Following is an incomplete list of people involved in research and development of Echo:

Original concept and implementation:

• John Holland (Univ. of Michigan & Santa Fe Institute)
• Terry Jones (then at Santa Fe Institute)

Echo researchers include:

• Simon Fraser (then at Santa Fe Institute)
• Peter Hraber (then at University of New Mexico and SFI)
• Stephanie Forrest (UNM & SFI)
• Jim Brown (UNM & SFI)
• Ginger Booth (Yale University)
• Oswald Schmitz (Yale University)

Other participants at the 1995 Echo workshop, and interested parties:

• Julian Adams (Univ. of Michigan)
• Jim Brown (Univ. of New Mexico)
• Marcus Feldman (Stanford University)
• Jim Levenick (Willamette University)
• Dan McShea (then at Santa Fe Institute)
• Bruce Milne (Univ. of New Mexico)
• Rick Riolo (Univ. of Michigan)
• Michael Cohen (Univ. of Michigan)

1. Forrest, S. and T. Jones. 1994. Modeling complex adaptive systems with Echo. pp. 3--21 in R.J. Stonier and X.H. Yu, eds. Complex Systems: Mechanisms of Adaptation. IOS Press, Amsterdam.
   
   
2. Holland, J.H. 1994. Echoing emergence: Objectives, rough definitions, and speculations for Echo--class models. in G.A. Cowan, D. Pines and D. Meltzer, eds. Complexity: Metaphors, Models and Reality. Addison--Wesley, Reading, MA.
   
   
3. Holland, J.H. 1996. Echoing emergence: Objectives, rough definitions, and speculations for Echo--class models. in G.A. Cowan, D. Pines and D. Meltzer, eds. Complexity: Metaphors, Models and Reality. Addison--Wesley, Reading, MA.
   
   
4. Jones, T. and S. Forrest. 1993. An Introduction to SFI Echo. Technical Report 93-12-074, Santa Fe Institute, Santa Fe NM. Available via anonymous ftp from ftp.santafe.edu:pub/echo/how-to.ps.Z.