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People on this list may be interested in
Krause, A.E., K.A. Frank, D.M. Mason, R.E. Ulanowicz, and W.W.
Taylor.  2003. Compartments revealed in food-web structure. Nature 426:282-285

-- the current issue of Nature.

In the paper we identify cohesive subgroups in food webs, with implications
for how ecosystems might react to invading species.


The press release for the article is below






NEW STUDY REVEALS EXISTENCE OF COMPARTMENTS LIKE SOCIAL CLIQUES IN NATURAL
FOOD WEBS

Innovative research published this week in the journal Nature

A new study, published this week in the journal Nature, has revealed the
existence of what in human interactions would be referred to as "cliques"
in natural food webs.  This research examined what ecologists have
previously theorized: that plants and animals organize themselves into
cliques, just as humans do. These cliques, also known as compartments, are
groups of species in a food-web that interact more frequently with each
other than with species outside of that compartment.  Strong interactions
exist among species within compartments and weaker interactions exist
between individual compartments.  This research contributes to a more
sophisticated understanding of food web dynamics by illustrating how
species interact and, thus, how they impact each other.  This better
understanding of food webs will help natural resource managers make better
management decisions that affect food webs.

Food webs are multiple interconnecting food chains. Predators are likely to
have more than one prey and prey are likely to have more than one predator,
thereby creating a web of interactions, not a chain. A common approach of
understanding how species interact in food webs is to categorize them into
trophic -- or hierarchical --levels, where groups of species with similar
food resources and predators are associated with each other.  The trophic
level concept alone, however, provides an incomplete understanding of
food-webs, because it only provides one view of the picture; it looks at
which species are competitors, but not at the other associations species
make in the food web.  For example, in economics, people's purchasing
decisions are not solely influenced by the decisions made by their
neighbors, who are likely in the same economic bracket (or same
hierarchical level).  Rather, people are also influenced by their friends,
who may be in another economic bracket, but in a same clique or compartment.

The discovery of compartments within food webs provides a more advanced
understanding of species interactions with each other in the
environment.  The research, published this week in Nature,applies
principles for describing social systems to food webs--an exciting new way
to view food web structures and to identify compartments in food-webs.  The
scientists employed a recently developed social network method.  "It has
been proposed that social systems are more efficient and durable when
composed of subgroups in which interactions are concentrated," said Dr. Ken
Frank of Michigan State University and member of the research team. "This
appears also to be the case for food-web compartments in ecology, and this
method identifies compartments in which interactions are concentrated."Dr.
William Taylor of Michigan State University and a member of the research
team added: This study highlights the importance and necessity of
interdisciplinary science and problem solving.

A simple illustration of the trophic and compartment concepts is to
consider state governments. The trophic level model would put the US
governors in a category, the state representatives in another category, and
the people in a third category.  The compartment model, however, groups
people by state, so a state would be one compartment, with a governor, the
representatives, and people having strong interactions with each other, and
weaker interactions with other compartments, the other states.

"The compartment method of measuring species interactions in an ecosystem
has its benefits," said Ann Krause of Michigan State University, a member
of the research team.  "This method is more systematic and rigorous, as it
assigns species to certain compartments based on observed research -- not
based on a researcher's guess -- and tests the results for
significance.  Moreover, if compartments can be found to enhance stability
in nature like they were found to do in theoretical research, we now have
another tool with which to better understand stability in
ecosystems.  Stability is important for maintaining ecosystem health.

"This study will provide a mechanism for others to study and measure the
stability of food-webs," added Dr. Doran Mason of the Great Lakes
Environmental Research Laboratory, a member of the research
team.  "Understanding food web stability significantly enhances our
understanding of ecosystems which, of course, helps biologists and managers
in their efforts to protect and improve the system.  With future
applications based on this research, we may find that managers should also
focus on maintaining compartments in food webs, which are whole groups of
species, not just maintaining the population of a single species, to
maintain ecosystem health and integrity."

This research is a collaborative among scientists Ann E. Krause, Kenneth A.
Frank, and William W. Taylor from Michigan State University's Department of
Fisheries & Wildlife; Robert E. Ulanowicz from the University of Maryland;
and Doran M. Mason of the National Oceanic and Atmospheric Administration's
Great Lakes Environmental Research Laboratory.  This research was funded by
the Great Lakes Fishery Commission, the National Institute of Child Health
and Human Development, and the National Science Foundation. Contact
information for members of the research team is as follows:

Krause: (734) 662-3209 x.21 ([log in to unmask])

Frank: (512) 475-8642 ([log in to unmask])

Taylor: (517) 353-3048 ([log in to unmask])

Ulanowicz: (410) 326-7266 ([log in to unmask])

Mason: (734) 741-2148 ([log in to unmask])


Public relations coordinated by
1300 EST, NOV. 19, 2003 Marc Gaden, Great Lakes Fishery Commission,
734-662-3209 x. 14

      Patricia Stewart, Michigan State University, 517-355-1821

       Jana Goldman, Nat. Oceanic and Atmos. Admin., 301-713-2483


----------------------------------------------------------------------------------




Those interested in work in social networks and ecosystems might also check
out work by Jeffrey Johnson and Steve Borgatti

Johnson, J. C., Borgatti, S. P., Luczkovich. J. J., & Everett, M.
G.  Network role analysis in the study of food webs:  an application of
regular role coloration.  J. Soc. Structure 2:  published online at
http://zeeb.library.cmu.edu:7850/JoSS/johnson/RoleAnalysis.html (2001)  --
Johnson's home page
  http://personal.ecu.edu/johnsonje/foodwebs.htm

And also

Girvan, M. and Newman, M. E. J. Community structure in social and
biological networks.  Proc. Natl. Acad. Sci. USA 99, 8271-8276 (2002).






Ken Frank
Population Research Center
The University of Texas at Austin
1 University Station G1800
Austin, Texas 78712-0544
http://www.msu.edu/~kenfrank/

e-mail: [log in to unmask]
phone: 512-475-8642
Fax: (512) 471-4886


Note I am on leave from Michigan State
where I am a professor in Education and
Fisheries and Wildlife

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