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10 | Foundations of agro-zoocoenology
He recognized several factors leading to dynamical change in an animal
“community” and discussed each. These are diurnal changes, seasonal changes,
and successional changes. All of these discussions relate to temporal persistence
of populations and “stability” of the trophic web. He notes that in practice,
temporal persistence can be difficult to determine because populations may
be present below the detection threshold of the sampling method, and because
their life history may require their periodic disappearance (diapause,
hibernation, torpor, stage-specific alternation of habitats). He considers
“communities” to be dynamic and ever-changing and suggests that it is more
important to consider how and why they change than to consider the stability
of any single observed “community”. This contrasts sharply with the food
web research program stimulated by May (1972) of investigating the stability
of model food webs. I suppose the key difference underlying Szelényi’s
perspective is that he recognized the tremendous difficulties to describe an
animal “community” and the dynamic nature of these communities.
A key weakness in Szelényi’s approach is that it requires a priori life history
knowledge on all the life stages of the species in a sample. It is from this
information that he can construct the trophic connections among the
populations. Identifying trophic interactions remains an active area of research
today, with cutting edge molecular methods being used now to produce a
third-generation of ecological food webs with greater accuracy. Thus, much
of Szelenyis thinking was before his time, and some of his ideas can only be
addressed as these third-generation food webs are compiled.
Most of Szelenyis ideas are of historical interest and it is interesting to see
that many of his ideas are reflected in the subsequent history of food web
ecology. It makes me wonder how our present ideas would have developed
had his work been more widely known and appreciated. In any event, his
work represents a total commitment to understanding real food webs as they
exist in nature and his efforts to tackle the problems that arise provide fuel
for thought even today.
David A. Andow
Distinguished McKnight University Professor
Fellow of the Entomological Society of America
Brasilia, Brazil, 24 November 2021