Guild Structure and Community Organization

Guild -- clusters of functionally similar species, such as foliage-gleaning insectivorous birds, diurnal terrestrial insectivorous lizards

Colwellian plots of standard deviation in niche overlap versus rank of neighbor in niche space

Macrodescriptors -- relative abundance, species diversity, trophic levels, and food webs.

Identification of appropriate aggregate variables is not only essential, but also constitutes a double-edged sword: such macrodescriptors enable progress but simultaneously constrain its direction(s).

Epiphenomena arise from pooling component populations -- trophic levels, guilds, subwebs, and ecological pyramids.

Do communities possess truly emergent properties that transcend those of mere collections of populations?

Major pitfall -- communities are not designed directly by natural selection for efficient and orderly function

Antagonistic interactions at the level of individuals and populations (such as competition, predation, parasitism and even mutualisms) frequently impair aspects of ecosystem performance while enhancing other properties

For example, consider prey-predator interactions -- selection operating on individual prey organisms favors escape ability, which in turn reduces the rate of flow of matter and energy through that trophic level, decreasing ecological efficiency but increasing community stability
Predators, however, evolve better ability to capture their prey, which increases efficiency of flow of energy of through trophic levels but reduces system stability

More thought needs to be devoted towards attempts to connect community-level properties with those of individuals in populations


Direct pairwise versus indirect effects in complex networks of interacting species -- species must be considered within the context of the entire community in which they exist (cannot isolate pairs)

How to depict a complex network of interacting species in an understandable manner?

A hybrid protocol for the analysis of community structure

Observed resource utilization matrices are randomized to form pseudo-communities (conserved zeros vs. scrambled zeros)

These randomized communities are compared with their real prototypes to detect statistically significant differences

Anatomical Correlates of Ecology

Head length, hindleg length
Morphometric hypervolumes
Principal Components Analysis

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Last updated 20 March 1997 by Eric Pianka