Community Ecology The course webpage: http://www.kharms.biology.lsu.edu/BIOL7083Spring2013.html.

Community Ecology The course webpage:

Geography Resources Phylogeny Community
Community – collection of species that occur at the same place & time, circumscribed by natural (e.g., serpentine soil), arbitrary, or artificial (e.g., 1-m2 quadrat) boundaries Many prefer a more restrictive definition in which species must interact to be included, e.g., Whittaker (1975) Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Whittaker, Robert H Communities and Ecosystems, 2nd ed. MacMillan, New York, NY. Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Community
Taxon – phylogenetically related group of species; a clade E.g., Mammalian Order Rodentia Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Taxon Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Community Guild
Guild – a group of species “without regard for taxonomic position” that “exploit the same class of environmental resources in a similar way” (Root 1967) E.g., granivores Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Root, R. B The niche exploitation pattern of the blue-gray gnatcatcher. Ecological Monographs 37: Taxon Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Local guild Community Guild
Local guild – a group of species that share a common resource and occur in the same community (Root 1967) E.g., Sonoran Desert granivores Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Root, R. B The niche exploitation pattern of the blue-gray gnatcatcher. Ecological Monographs 37: Taxon Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Local guild Community Guild Assemblage
Assemblage – a group of phylogenetically related species within a community Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Taxon Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Local guild Community Guild Assemblage
Assemblage – a group of phylogenetically related species within a community a.k.a. “Taxocene” (Hutchinson 1967) E.g., Sonoran Desert rodents Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Taxon Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Local guild Community Guild Ensemble
Assemblage Ensemble – a phylogenetically bounded group of species that use a similar set of resources within a community E.g., Sonoran Desert granivorous rodents Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Taxon Redrawn from Fauth et al. (1996)

Geography Resources Phylogeny Local guild Community Guild Ensemble
Assemblage E.g., granivorous rodents, pond-breeding salamanders… Fauth, John E., J. Bernardo, M. Camara, W. J. Resetarits, Jr., J. Van Buskirk & S. A. McCollum Simplifying the jargon of community ecology: A conceptual approach. The American Naturalist 147: Taxon In this course any collection of two or more species is “fair game” for close scrutiny Redrawn from Fauth et al. (1996)

Robert H. MacArthur’s definition of Community
I may be particularly biased in favor of MacArthur’s definition (found in MacArthur [1971] in Farner & King, eds., Avian Biology; see J. A. Wiens [1989] The Ecology of Bird Communities, pg. 3), since it most flexibly fits the types of “communities” on which my research focuses. Kaspari, Michael Knowing your warblers: thoughts on the 50th anniversary of MacArthur (1958). Bulletin of the Ecological Society of America. October: “Any set of organisms currently living near each other and about which it is interesting to talk” (MacArthur 1971) Painting by D. Kaspari for M. Kaspari (2008) – anniversary reflection on MacArthur (1958)

Community Ecology Some historic landmarks
Community Ecology has matured from purely descriptive studies (i.e., description & analysis of patterns) to mechanistic studies (i.e., investigations into processes) that aim to improve our explanatory & predictive abilities In any case, the tradition of good Natural History is not ignored by the best modern practitioners Consider this quote from a remarkable naturalist (Henry David Thoreau) re “faith in a seed” – “Though I do not believe that a plant will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders.” “Though I do not believe that a plant will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders.” (H. D. Thoreau ~1860)

Community Ecology Some historic landmarks Charles Darwin (1809 - 1882)
Not the first “ecologist,” but clearly recognized the importance of organisms’ interactions (intraspecific, interspecific & with their abiotic environments) for evolution by natural selection Ernst Haeckel ( ) coined “oekologie” for the study of Darwin’s multifaceted “struggle for existence” Photo from WikiMedia Commons

On biotic interactions: “Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!” (Darwin 1859) Photo from WikiMedia Commons

On abiotic processes, e.g., abiotic disturbance: “If turf which has long been mown… be let to grow, the most vigorous plants gradually kill the less vigorous, though fully grown plants; thus out of 20 species growing on a little plot of mown turf (3 feet by 4 feet) nine species perished from the other species being allowed to grow up freely…” (Darwin 1859) Photo from WikiMedia Commons

Ellen Swallow Richards ( ) Chemist who probably “created and taught the first ecology curriculum” in the U.S. and may have introduced the term “ecology” into the English language (from Ernst Haeckel’s “oekologie”) Damschen et al Visibility matters: increasing knowledge of women’s contributions to ecology. Front. Ecol. Environ. 3: Photo from WikiMedia Commons; for further details see Damschen et al. (2005)

Community Ecology Some historic landmarks Stephen Forbes (1844 - 1930)
One of the earliest ecologists to examine multiple, cross-trophic level interactions simultaneously within an explicitly evolutionary framework Wondered how in spite of a constant “struggle for existence” some balance is nevertheless maintained in ecosystems (see: The lake as a microcosm, 1887) Photo from Balance with respect to certain emergent, community-level properties, such as total biomass, nutrient flux, etc. Photo from

Community Ecology Some historic landmarks Henry Cowles (1869 - 1939)
A pioneer of “dynamic ecology,” especially on the sand dunes of Lake Michigan Emphasized both static & dynamic patterns in Nature! Photo of Cowles from Photo of Lake Michigan sand dune from Photo of Cowles from Photo of Lake Michigan sand dune from

In the grand traditions of Alexander von Humboldt ( ; the “father of biogeography”) & Alfred Russel Wallace ( )… Clinton Hart Merriam ( ) also noticed that geographic changes in physical conditions often coincide with changes in biota Merriam devised Empirical Life Zones (similar biotic changes with increased elevation or latitude) Geographic patterns!

Leslie Holdridge ( ) – devised Theoretical Life Zones (1947) Geographic patterns! Image from WikiMedia Commons

Clements vs. Gleason (1920s & 1930s) Frederic Clements ( ) – thought succession always reached a predictable climax community; viewed communities metaphorically as “superorganisms” Henry Gleason ( ) – proposed the “individualistic concept” of communities; discrete populations whose patterns of distribution and abundance give rise to communities as epiphenomena Clements’ concept of communities as “superorganisms” -- essentially that the particular collection of organisms in a community are so thoroughly integrated in their interactions that substitutions could lead to collapse. Gleason emphasized the “individualistic” (not necessarily independent) distribution of populations on landscapes, especially along gradients.

Robert H. Whittaker ( ) His gradient analyses helped end the Clements-Gleason debate Figures from For modern use of “Gleasonian” vs. “Clementsian” patterns see: Leibold, M.A. & Mikkelson, G.M Coherence, species turnover, and boundary clumping: elements of metacommunity structure. Oikos, 97, 237–250. Presley, S. J., L. M. Cisneros, B. D. Patterson & M. R. Willig Vertebrate metacommunity structure along an extensive elevational gradient in the tropics: a comparison of bats, rodents and birds. Glorbal Ecology & Biogeography… Photo from WikiMedia Commons; figures from

We continue to need good descriptions of patterns, often supported by sound, quantitative techniques E.g., Bray & Curtis (1957) introduced ordination methods to define plant communities in Wisconsin See: The Ordination Web Page ( It would be possible to teach an entire course in “Community Ecology” based on methods for defining boundaries among communities, whereby communities are defined taxonomically, statistically, or interactively (as explained in Morin 1999). Even so, this course will focus instead on the processes that give rise to patterns in communities, however, they might be defined. E.g., the Ecological Society of America, The Nature Conservancy, the U.S. Geological Survey, the U.S. National Park Service & others collaborate to continue to refine the National Vegetation Classification Standard (NVCS)

Margaret Davis (b. 1931) Her paleo-ecological perspective has helped increase awareness of historical contingencies Photo of pollen from Photo of Davis from U. Minnesota; photo of pollen from

Community Ecology Some historic landmarks Joseph H. Connell (b. 1923)
Heralded as milestones in ecology, his studies demonstrated the utility of field experiments for answering ecological questions; empirically assessed multiple hypotheses for intertidal zonation The concept of equifinality was formalized by Ludwig von Bertalanffy (1968; founder of General Systems Theory) – multiple hypotheses or mechanisms can equally explain or generate the same pattern Contrast Connell’s experimental work with Doty (1946; Ecology 27: ), in which non-experimental work demonstrated striking algal zonation correlated with dramatic non-linear steps in time of immersion at various heights. See also Wethey’s work on the same species of barnacles along the New England coast (1984, Biological Bulletin). Photo from UCSB

Observations: Balanus balanoides – Larger barnacle, generally found lower in the intertidal Chthamalus stellatus – Smaller barnacle, generally found higher in the intertidal Photo from UCSB

Photo from UCSB

Observations: Balanus balanoides – Larger barnacle, generally found lower in the intertidal Chthamalus stellatus – Smaller barnacle, generally found higher in the intertidal Pattern = zonation Mechanistic hypotheses yield various predictions… Why might these patterns exist? Photo from UCSB

Hypotheses: Differential physiological tolerances to desiccation and submersion Interspecific competition Predation (e.g., Thais lapillus is a predator of Balanus balanoides) Photo from UCSB

Exclusion experiments, results & conclusions: The absence of competitors & predators produced no change in upper level of distributions For Chthamalus, removing Balanus increased downslope survivorship & distribution For Balanus, removing Thais increased downslope survivorship & distribution Photo from UCSB

Photo from UCSB; figure from Connell (1961; one of Connell’s 5 Science Citation Classics)

Robert H. MacArthur ( ) More than most of his predecessors, MacArthur demonstrated the utility of simplifying assumptions combined with mathematical rigor for exploring ecological problems Criticisms: oversimplification; over-emphasized competition & equilibria Among the main criticisms of the approach: it’s too strongly focused on competitive interactions and equilibrium conditions. Wilson & Hutchinson – “Inevitably his approach was condemned by some ecologists as oversimplification, but… it energized a generation of young population biologists and transformed a large part of ecology…” (see pg. 292, Nancy Slack’s biography of G. E. Hutchinson). Photo from Wikipedia

G. Evelyn Hutchinson ( ) Conceived of fundamental vs. realized niche spaces or hyper-volumes “Ecologists use the metaphor of the ‘ecological niche’ to express the idea that plant and animal species play certain roles in the ecological community” (Kingsland 2005, pg. 1) Kingsland, Sharon The Evolution of American Ecology: Johns Hopkins Press, Baltimore, MD. Photo from Yale Peabody Archives

Community Ecology Some historic landmarks G. Evelyn Hutchinson
E.g., Hutchinsonian ratios A ratio of ~ 1.3 in size occurs between pairs of coexisting species, possibly owing to interspecific competition Hutchinson (1951) correctly attributed the original idea of competitively-generated size differences to Huxley; see Carothers (1986). See Simberloff (1983) for a review. The idea & disagreement over how to test it helped motivate the development of null models in ecology Figure from Gotelli & Graves (1996, pg. x)

“Null hypotheses [models] entertain the possibility that nothing has happened…” (Strong 1980) “A null model is a pattern-generating model that is based on randomization of ecological data or random sampling from a known or imagined distribution. The null model is designed with respect to some ecological or evolutionary process of interest. Certain elements of the data are held constant, and others are allowed to vary stochastically to create new assemblage patterns. The randomization is designed to produce a pattern that would be expected in the absence of a particular ecological mechanism…” (Gotelli & Graves 1996)

Community Ecology Some historic landmarks Stephen P. Hubbell (b. 1942)
Neutral theory… asks how well community-level patterns conform to predictions under the simplifying assumption that all individuals are equal (in terms of probability of recruiting, dying, and replacing themselves through reproduction) Among the main criticisms of the approach: some manifestations of the idea assume species’ traits do not matter for determining species’ abundance and distribution patterns. See: Gotelli & McGill Null versus neutral models. What’s the difference? Ecography 29: See: Darwin (1859) – “When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this!” (pg. 125 in Penguin Classics paperback of 1st ed.) “When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this!” (C. Darwin 1859) Photo from UCLA

Community Ecology Patterns & Processes
Patterns – any observable properties of the natural world, often expressed as variable quantities or distributions (since variation characterizes every level of biological organization) Processes – the causal mechanisms that give rise to the patterns Mechanistic explanations provide guidance for forecasting or predicting future patterns, which is especially important in response to anthropogenic change and in the context of restoration. See also Watt (1947) Pattern and process in the plant community – J. Ecology

Processes that determine local community composition
(most of which produce community structure that wouldn’t be predicted by null models) Redrawn from Morin (1999, pg. 27)

Processes that determine local community composition
(most of which produce community structure that wouldn’t be predicted by null models) Community A Community B What relative contributions do the various processes make (and have made) towards maintaining (and originally creating) differences between communities A and B? Redrawn from Morin (1999, pg. 27)

Parallels between Community Ecology & Population Genetics
These affect biological variants, i.e., alleles or species Processes Drift Migration Selection Abiotic environment Biotic interactions (e.g., competition, predation, etc.) Speciation … and extinction (owing to drift & selection) Primary patterns (across space & time) Emergent patterns From Vellend & Orrock (2010): “Both population and community ecology are essentially concerned with variation over space and time in the relative abundance and diversity of discrete biological variants: alleles or species, respectively. Four logically distinct processes can change the abundances and diversity of biological variants (Vellend & Geber 2005).” Productivity Species diversity Stability Species composition (identity & traits) Food-web connectance Species abundances Etc. Redrawn from Vellend & Orrock (2010)

Global community Drift Selection Speciation Migration Migration Regional community Drift Selection Speciation Local community Migration Migration From Vellend & Orrock (2010): “Both population and community ecology are essentially concerned with variation over space and time in the relative abundance and diversity of discrete biological variants: alleles or species, respectively. Four logically distinct processes can change the abundances and diversity of biological variants (Vellend & Geber 2005).” Drift Selection Speciation Redrawn from Vellend & Orrock (2010)

Global community Drift Selection Speciation Migration Migration Regional community Drift Selection Speciation Migration Migration Local community A Local community B From Vellend & Orrock (2010): “Both population and community ecology are essentially concerned with variation over space and time in the relative abundance and diversity of discrete biological variants: alleles or species, respectively. Four logically distinct processes can change the abundances and diversity of biological variants (Vellend & Geber 2005).” Drift Drift Selection Selection Speciation Speciation Redrawn from Vellend & Orrock (2010)

Parallels between Community Ecology & Evolutionary Theory
Global community “the central narrative of evolutionary theory is that variation originates from random mutation and then natural selection in a local setting acts upon this variation to produce organic diversity” In a parallel fashion the “formational theory of communnity ecology” could be: “local interactions act upon the species arriving at the community’s boundary to produce a diversity of communities” Supply-side ecology Supply-side ecology Local community A Local community B Local interactions Local interactions Roughgarden (2009)

Pair-wise species interactions
(owing to acquisition or assimilation of resources, etc.) Influence of species A - (negative) 0 (neutral/null) + (positive) A B Competition - A B Amensalism - A B Antagonism (Predation/Parasitism) + - - A B Amensalism - A B Neutralism (No interaction) A B Commensalism + Influence of Species B A B Antagonism (Predation/Parasitism) - + A B Commensalism + A B Mutualism + + Redrawn from Abrahamson (1989); Morin (1999, pg. 21)

Pair-wise species interactions
Interactions are often asymmetric, even when the sign of the interaction is the same in both directions (e.g., obligate for one organism, but facultative for the other) Species B _ / + + / + A better way to portray pair-wise species interactions might be via a bi-plot of the influence of each species on the other on the two axes, in which each axis ranges from the maximum possible degree of negative influence to the maximum possible degree of positive influence. Should such a figure be scaled on a per capita basis? How would one determine the magnitude of the end points of each axis? Perhaps it should be 3-D, with the third axis being a relevant, abiotic environmental gradient. For example, for mutualists – are they critical or convenient from a given partner’s perspective? Species A _ / _ + / _

Laws in Community Ecology
In any case, the laws of physics & chemistry apply (e.g., thermodynamics & stoichiometry) Are there “laws” specific to Ecology, and Community Ecology in particular? I have seen the conclusions of Connell’s experiments generalized as “Connell’s rule,” i.e., that upper limits in inter-tidal zonation are set by physical processes, whereas lower limits are set by species interactions. See: J. Lawton (1999) [evolution by natural selection is an underlying “law” of ecology] See: P. Turchin (2001) [exponential population growth when resources are unlimited is an underlying “law” of ecology] See: Roughgarden (2009)

To separate Ecology and Evolution into separate
disciplines is somewhat artificial …just as is completely separating Community Ecology from other related sub-disciplines Nothing in biology makes sense except in the light of evolution (T. Dobzhansky 1973) All organisms interact with other organisms, both conspecific and heterospecific, and their environments; i.e., the evolutionary play takes place within an ecological theater (G. E. Hutchinson 1965) I hope this brief introduction to Community Ecology convinces you that we will take a broad view of the subject: From interactions between pairs of species through global patterns of diversity. Ecologists and evolutionary biologists must recognize and embrace the complexity of natural ecosystems to understand them, and their components, much as Zen masters recognize and embrace the interconnectedness of the universe (D. P. Barash 1973)

Community Ecology The course webpage: http://www.kharms.biology.lsu.edu/BIOL7083Spring2013.html.

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Community Ecology The course webpage: http://www.kharms.biology.lsu.edu/BIOL7083Spring2013.html.

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