Spatial Population Models for Animals - Environmental Modelling: Finding Simplicity in Complexity - page 223

Ultimately, decisions about what sort of model to apply
in any given situation depends on the problem at hand,
including the relative weight placed on model tractabil-
ity versus model realism. Is the goal to generate specific
prediction? Or is it to demonstrate the potential role of
hitherto unexplored factors? Finding the appropriate bal-
ance between tractability and realism is a major challenge
for all modellers, but again, there is no right answer.
In this chapter we presented a spatial model of drift
by invertebrate larvae in streams. From this example we
draw several key points. First, the drift of invertebrates
in streams has been the focus of a considerable amount
of research yet is empirically challenging (e.g. the diffi-
culty of tracking individual larvae, etc.). Using a relatively
simple spatial model we show how such a model can
produce quite complex and unexpected outcomes when
applied to the drift phenomenon. At the same time, the
model presented a possible solution to some puzzling dis-
crepancies in drift distances observed in several previous
empirical studies.
The recent interest in spatial patterns and processes
in ecology has resulted in the development of a wealth
of theory on spatial ecology. However, empirical test-
ing of this theory has not proceeded as quickly; in part
because of inherent problems in experimental design and
analysis at extended spatial scales, but also because some
of this spatial theory has not been framed in an obvi-
ously testable manner. We encourage a greater discourse
between modellers and empirical researchers in resolving
these issues.

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13.6 Acknowledgements

Ralph Mac Nally is thanked for useful comments on an
earlier draft of this chapter.

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