WILSON AND AGNEW, CHAPTER 5: ASSEMBLY RULES
How important are null models in ecology? Do all patterns need to be tested against a
null model to be “proven”?
Wilson and Agnew define assembly rules as restrictions on species patterns due to
species interactions, but not environmental responses. Can species interactions and
environmental responses really be treated as isolated topics?
Is environmental characterization of species distributions really the “easy task of
community ecology” and therefore uninteresting?
Is Wilson and Agnew’s approach for ruling out environmental variation adequate? Are
there other ways besides the “patch model” for mitigating pseudoreplication?
The work of Whittaker and other ecologists has suggested that species boundaries are
randomly-spaced rather than clustered along environmental gradients. Are there
theoretical reasons to continue searching for clustered boundaries on gradients?
If conditions were truly identical, would the outcome of succession (species sorting) also
be identical? What factors in natural communities seem to be most responsible for
preventing successional convergence?
In section 6, Wilson and Agnew suggest that species with similar traits are not likely to
coexist at a site, whereas in section 8 they suggest that traits are likely to converge at a
site. What is the distinction between these hypotheses, and how can they be reconciled?
Most of the experiments testing for guild proportionality are conducted at very fine
scales. If significant guild proportionality is observed at these scales, is this evidence of a
relevant assembly rule in plant communities? What scale is relevant? At what scale do
communities occur?
Why would we expect more than one species per guild?
Do all species (or guilds) have an equal probability of arriving? Is this an assumption of
the null patch model?
Wilson and Agnew propose that removal experiments are one way to test for guild
proportionality because if species from one guild are removed then, in order to maintain
proportionality, any increase in species will likely be from the same guild. Is this a
logical argument? What other outcomes might we expect? Will the outcome depend on
the type of species removed or the time since removal?
What do you think about the method for determining intrinsic guilds? Can all species
realistically be assigned to two guilds?
Why is guild proportionality generally only observed in the herb layer?
What do Wilson and Agnew conclude regarding guild proportionality?
Why is invasion limited in tropical forests? Can this provide insight into assembly rules?
Are there different assembly rules for different habitats?
SUMMARY QUESTIONS: Did any sections of this chapter seem irrelevant or only
tangentially related to the topic? Which assembly rules were best supported, what are the
major conclusions and are you convinced?