Community Ecology Processes, Models, and Applications

to compare the different model predictions (e.g.
McGillet al. 2006), several models can predict the
same pattern of relative abundances as the neutral
model (reviewed in Chaseet al. 2005). In addition,
statistically distinguishing between different mod-
els using empirical species-abundance distributions
is not always straightforward (McGillet al. 2007).
This indicates the limitations of using one pattern,
especially relative abundance patterns, to discern
among the validity of the assumptions underlying
the different perspectives.

The four models make different assumptions re-

garding how species respond to environmental and

spatial gradients, and thus make different predic-

tions regarding patterns of community structure

along those gradients. We do not go into detail

regarding the theoretical reasoning behind each of

the predicted patterns here, but instead simply re-

view them in Table 5.1 (for more detail, see Chase

et al. 2005). We start with the simplest model, and

then move to models using increasingly complex

assumptions.

Table 5.1Summary of predictions from the four metacommunity modelling frameworks (modified from
Chaseet al.2005)

Model prediction

Effect Neutral Patch dynamics Species sorting Mass effects

Overall local
diversity

Extinction and

colonization

balance

Extinction and

colonization balance

Depends on species

interactions

Depends on species
interactions and
colonization/
extinction
Overall
regional
diversity

Extinction and

speciation

balance

Depends on competition–

colonization

trade-off

Same as above and

degree of habitat

heterogeneity

Same as above and
degree of habitat
heterogeneity
Relative
species
abundance

Zero-sum

multinomial

(skewed towards

rare species)

Variable depending on

level of migration and

degree of interaction

Variable depending

on environmental

conditions

Variable depending on

level of migration

Dispersal
effects on
local
diversity

Increase First increase, then

decrease

(hump-shaped)

No effect First increase, then

decrease (hump-

shaped)

Dispersal
effects on
regional
diversity

Decrease Decrease No effect Decrease

Dispersal
effects on
b-diversity

Decrease Global: no effect

Local: decrease

No effect Global: decrease

Local: decrease

Local
disturbance

Return immediately Unpredictable Return immediately Return following
succession
Regional
disturbance

Random walk Return following

succession

Return immediately Return following
succession
Temporal
variation:
local

Variable Variable Static unless

environment

changes

Static unless
environment
changes
Temporal local
variation:
regional

Variable Static unless environment

changes

Same as above Same as above

INCREASING SPATIO-TEMPORAL SCALES 59