The importance of nematodes in ecosystems and their
advantages as biological indicators
H FERRIS
University of California, Davis, California 95616, USA
ABSTRACT
That nematodes occupy almost every conceivable niche on the planet, and that
different habitats support characteristic assemblages, has been eloquently documented.
The structure of the soil food web and its component nematode assemblages are
shaped by resource availability, physico-chemical characteristics of the environment,
contamination, disturbance, parasitism and predation. Ecosystems exhibit dynamic
equilibrium states which fluctuate with energy and food input, nutrient levels, predatorprey relationships and disturbance. The states of the systems may be indicated by
characteristic assemblages of functional guilds, that is, organisms representative of
groups with the same feeding habits and similar life history characteristics. Ecosystem
functions are the physical, chemical, and biological processes that contribute to the
maintenance, regulation and change of equilibrium states. Ecosystem services are the
subjectively-determined beneficial outcomes which result from ecosystem functions.
Nematodes contribute to ecosystem functions of resource transfer through herbivore
and detritivore channels; they provide regulatory services through predation on
opportunistic species, services of nutrient mineralization and the distribution of bacterial
and fungal propagules to new resources. Undoubtedly, there are other services yet to be
discovered.
Ecosystem symmetries may be reflected in the consistency of functional guilds
represented by different taxa. Family-level categorization of nematodes appears to
provide sufficient resolution to infer similarity of functional guilds across systems.
Clearly that involves some assumptions of convenience and studies of the biology of
individual taxa will be necessary for more precise allocation of taxa to functional guilds.
The linear arrangement of taxa, from colonizers of disturbed systems to inhabitants of
undisturbed environments (Bongers, 1990), has evolved to a two-dimensional alignment
that allows assessment of both enrichment and stability of soil systems (Ferris et al,
2001).
The attributes of nematodes that confer advantages as biological indicators are their:
ubiquity, abundance, signal persistence, and that their feeding habits can often be
inferred from stomal features. In sustainable systems, the management of services
provided by nematodes and other soil food web organisms can be achieved by
regulating the nature and flow of resources through trophic channels and the
maintenance of an environment favorable to higher trophic level organisms.
References
Bongers T. 1990. Oecologia 83: 14–19.
Ferris H, Bongers T, de Goede RGM. 2001. Applied Soil Ecology 18:13–29.