TABLE CONTENTS

A Perspective on Diversity within Nematode Feeding Groups across
Ecosystems
Yeates, G.W.
Landcare Research, Private Bag 11052, Palmerston North 4442, New Zealand
Recently there has been strong interest in nematode diversity and the use of nematodes as
indicators of soil conditions. Key papers on feeding groups, a maturity index and structural
indices reflected current understanding of nematode biology. Soil nematodes contribute to
ecosystem services so potential build-up of populations, or their contribution to ecosystem
processes, across regions and ecosystems are relevant. What do we really know, or can
infer, about nematode biology on these scales? Plant nematologists consider the effects of
many plant-feeding nematodes in a given field - whether their spatial heterogeneity was due
to soil factors or plant traits. In some habitats plant-feeding nematodes are not abundant but,
given that these have been demonstrated to increase ‘leakage’ of photosynthate into the soil
microbial biomass, and thus enhance microbially-mediated nutrient cycling, with a paucity of
these plant-feeders there may be a rather different soil biology - assuming mealy bugs, aphids
and the like are not acting in their place. As a corollary, if the roots are strongly mycorrhizal a
different functional set of nematodes may be active. Knowledge of fungal-feeding nematodes
is developing. Some bacteria may be too large for particular bacterial-feeding nematode
species to ingest, but, on a wider scale, why do the bacterial-feeding nematode assemblages
in particular soils tend to be dominated by cephalobids, panagrolaimids, plectids or
rhabditids? Such questions can only be tested in comparable ecosystems. In annual or
cropping systems the decay of the annual crop is likely to overshadow other effects, although
seasonal patterns may be useful. In forests litter processes may be strongly influenced by
year-to-year climatic differences. Permanent grasslands or ecosystems on similar soils but
with contrasting functional pathways (e.g., mycorrhizal versus non-mycorrhizal) with may
provide the optimum ecosystem to investigate complementarity between, and diversity
within, nematode feeding groups.
5 th International Congress of Nematology, 2008 7