Dr. Paul A. Keddy
The Development and Use of Assembly Rules in
Predictive Community Ecology
Eva Hillmann
Spring 2014
Dr. Paul A. Keddy
• b.
Biography
May 29, 1953 (London, Ontario)
• Canadian ecologist/plant population ecology and
community ecology (eastern Canada and Louisiana)
• professor of ecology for 30 years; at University of
Guelph(1978-1982), University of Ottawa (19821999) and Southeastern Louisiana University (19992007)
• 150 peer-reviewed articles, 7 books (author), 2
books (co-editor)
Focus: principles that organize plant communities,
with particular emphasis on wetlands
Selected Publications and Research Interests
Tactics and strategies for ecological research
Keddy, P.A. 2005. Putting the plants back into plant ecology: six pragmatic models for understanding and conserving plant diversity.
Keddy, P. 1994. Reflections on the 21st birthday of MacArthur's Geographical Ecology - applications of the Hertzprung-Russel star diagram to
ecology.
Keddy, P.A. 1987. Beyond reductionism and scholasticism in plant community ecology
.
Community assembly rules
Keddy, P.A. 1999. Wetland restoration: the potential for assembly rules in the service of conservation.
Weiher, E., I. C. Wisheu, P.A. Keddy and D.R.J. Moore. 1996. Establishment, persistence, and management implications of experimental
wetland plant communities.
Weiher, E. and P.A. Keddy. 1995. Assembly rules, null models, and trait dispersion: new questions from old patterns.
Competition: gradients & competitive hierarchies
Twolan-Strutt, L. and P.A. Keddy. 1996. Above- and below-ground competition intensity in two contrasting wetland plant communities.
Gaudet, C.L. and P.A. Keddy. 1995. Competitive performance and species distribution in shoreline plant communities: a comparative approach.
Wilson, S. D. and P.A. Keddy. 1986. Measuring diffuse competition along an environmental gradient: Results from a shoreline plant community
.
Centrifugal organization
Wisheu, I. C. and P.A. Keddy. 1992. Competition and centrifugal organization of ecological communities: theory and tests.
Keddy, P.A. and P. MacLellan. 1990. Centrifugal organization in forests.
Coastal plain shoreline vegetation- Nova Scotia & Ontario
Wisheu, I. C., C. J. Keddy, P.A. Keddy, and N.M. Hill. 1994. Disjunct Atlantic coastal plain species in Nova Scotia: distribution, habitat and
conservation priorities.
Keddy, P.A. 1985. Lakeshore plants in the Tusket River Valley, Nova Scotia: the distribution and status of some rare species including Coreopsis
rosea and Sabatia kennedyana.
Keddy, P.A. 1981. Vegetation with Atlantic coastal plain affinities in Axe Lake, near Georgian Bay, Ontario
.
Great Lakes wetlands
Keddy, P. A. and Reznicek, A. A. (1986). Great Lakes vegetation dynamics: the role of fluctuating water levels and buried seeds.
Moore, D.R.J., P.A. Keddy, C.L. Gaudet and I. C. Wisheu. 1989. Conservation of wetlands: do infertile wetlands deserve a higher priority?
Awards
2009 Award of Excellence—Heritage and Ecology, Lanark County
2008 Champion for Nature Award, Mississippi Valley Field Naturalists
2007 National Wetlands Award for Science Research, Environmental Law Institute
2006 Lifetime membership, Society of Wetland Scientists
2006 Merit Award, Society of Wetland Scientists
2005 Team Achievement Award for Louisiana Ecosystem Restoration Study, USACE
2002 Highly Cited Researcher designation by the Institute for Scientific Information
(in top 0.5 of 1% of cited scientists in Ecology/Environment worldwide)
1999 Schlieder Endowed Chair for Environmental Studies, Southeastern Louisiana University
1992 Lawson Medal, Canadian Botanical Association
1991 Gleason Prize, New York Botanical Garden
Service awards: Committee on the Status of Endangered Wildlife in Canada (1998)
Canadian Council on Ecological Areas (1992)
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with
particular emphasis on wetlands
•Context
•Assembly rules
•Species pools
•Environmental filters
•Functional traits
•Response rules
•Deletion rules
•Addition rules
•Methodological considerations
•Mesocosm experiment
•Conclusions
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with
particular emphasis on wetlands
Context;
Central themes and the conceptualization of assembly
rules in community ecology
•Lewontin 1974
•Peters 1991
•Lawton 1992
•Keddy 1992
•Scheiner 1993
•Keddy 1993
•Scheiner 1994
How are communities assembled from species pools?
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with
particular emphasis on wetlands
Can we predict the future states of communities?
Keddy, 1999
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with
particular emphasis on wetlands
Can we predict the future states of communities?
Yes!....but we need to sift through the “crap” to
identify a few, key general principles
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with
particular emphasis on wetlands
•scale and level of organization
•variables
Population vs. community ecology
Population ecologists predict the properties of
aggregations of individuals.
Community ecologists predict the properties of
aggregations of populations.
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Keddy, 1992
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Keddy, 1992
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Assembly rules;
The constraints (rules) on community formation and
maintenance (assembly)
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Assembly rules;
The constraints (rules) on community formation and
maintenance (assembly)
3component parts;
•species pool
•environmental filter
•functional trait
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Assembly rules;
The constraints (rules) on community formation and
maintenance (assembly)
Objective;
•Predict which subset of total species pool in a region
will occur in a specified habitat
•Predict presence/absence
•Predict abundance
Keddy, 1999
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Environmental filter;
•Filter acts on traits unsuitable for the environment
•Species that comprise the community survive the filter
assembly rule
Keddy, 1992
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Functional trait;
Life history traits that allow organisms to tolerate different filters
Keddy, 1990
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Given
•A species pool
•A trait matrix
•List of environmental filters
Assembly rules would specify which subset of traits (therefore,
species possessing them) will persist in a particular habitat
Keddy, 1992
needs more work
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Assembly rules for wetlands;
Keddy, 1992, van der Valk, 1981
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Response rules;
•Grow out of assembly rules
•Specify how an initial species assemblage will respond when an
environmental factor is changed
Different from assembly rules;
•Initial vector of species already exists and must predict how
these species will respond to change in environmental condition
(deletion rules)
•Must re-examine species pool and trait maitrix for species likely
to replace those presently occurring (addition rules)
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Response rules;
Keddy, 1992
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Methodological considerations;
Building trait matrices
•requires understanding of key species-environment interactions
•Filters likely to operate
•Key traits which species possess to protect against filters
•Traits must be measured
•Simple (seed size, etc.)
•Or complex (growth rate, competitive ability)
•Need to develop bioassay for simple and complex attributes so
all species can be screened
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Species or functional groups?
•Species can be aggregated into groups sharing similar traits
•May be best to start developing assembly/response rules for
functional groups
•If predicting habitat function is the priority, it may matter little if
a functional group is represented by one or several species
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Conclusions;
Two clear goals for community ecology;
1. Devise efficient research strategies
2. Emphasize prediction rather than understanding
Moving forward;
•More quantitative relationships between traits and
environments need to be developed and specified
•Simple, effective screening techniques for functional traits
are needed
•More quantitative approaches to decision rules
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Mesocosm experiment;
•Experimental approach to assembly rules
•Put standard species pool through a set of environmental filters
for their ability to remove species from the species pool and alter
community composition
•Assumes no dispersal effects
Hypotheses;
1. At high fertility Typha would dominate and exclude the
smaller species regardless of treatment type
2. Species richness would be greatest in low fertility treatments
3. At low fertility, each treatment had greatest liklihood of
forming a distinct community
4. Of other treatments, water level would have strongest effect
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Methods;
•20 wetland plant species
•120 microcosm containers
•12 general wetland treatments
•2 fertility treatments
•5 replicates
Habitat variables;
•Water depth
•Timing and duration of flooding
•Leaf litter
•Soil texture
•Timing and duration of growing season
•Invasion by competitive species
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Results;
•As communities developed, abundance increased while species
richness decreased
•Fertile treatments had higher biomass and lower richness than
infertile treatments
•Only 2 habitat variables were significant;
•Water depth
•Fluctuation in water depth
*high water or fluctuations in water level associated with
lower species richness
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Keddy, 1995
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Keddy, 1995
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Keddy, 1995
Dr. Paul A. Keddy
Focus: principles that organize plant communities, with particular
emphasis on wetlands
Results/Conclusions;
•Evidence community composition constrained by assembly rules
•Consistent effects of water level, fertility and leaf litter
•Some habitat variables had no significant effects
•Community assembly can follow different pathways
•Convergence on a common endpoint suggests assembly
processes are highly constrained
Work Consulted
Keddy, P.A. 1999. Wetland restoration: the potential for assembly rules in the service
of conservation. Wetlands 19: 716-732.
Weiher, E., G. D. P. Clarke and P.A. Keddy. 1998. Community assembly rules,
morphological dispersion, and the coexistence of plant species. Oikos 81: 309-322.
Weiher, E. and P.A. Keddy. 1995. The assembly of experimental wetland plant
communities. Oikos 73: 323-335.
Keddy, P.A. 1992. Assembly and response rules: two goals for predictive community
ecology. Journal of Vegetation Science 3: 157-164.
Keddy, P.A. 1990. The use of functional as opposed to phylogenetic systematics: a first
step in predictive community ecology. in S. Kawano (ed.) Biological Approaches and
Evolutionary Trends in Plants. Academic Press, London.
Weiher, E. and P. Keddy (eds.) 1999. Ecological Assembly Rules: Perspectives,
Advances, Retreats. Cambridge University Press, Cambridge, UK. 418 p.
“Asking if there is a pattern in nature is akin to asking if bears shit in the woods.”
---Paul Keddy and Evan Weiher
Questions……….