We describe the spatial and temporal patterns in the abundance of nema
tode-trapping fungi and in suppression of nematodes in a coastal shrub
land. A previous study at this location (Bodega Marine Reserve, Sonoma
County, California) had documented a soil food chain in which an inse
ct-parasitic nematode consumes and kills the soil-dwelling larva of th
e ghost moth, which otherwise consumes and kills the bush lupine; the
patchy distribution of the nematode and lupine suggest the involvement
of nematophagous organisms, including nematode-trapping fungi. To tes
t our model (trapping fungi kill insect-parasitic nematodes, and there
fore ghost moths persist and kill lupines at some sites), we hypothesi
zed that sites with substantial lupine mortality would contain larger
numbers of nematode-trapping fungi and would be more suppressive to ne
matodes than would sites with little lupine mortality. Soil was collec
ted from eight sites (four with substantial lupine mortality and four
with little lupine mortality) at 2-mo intervals for I yr and subjected
to dilution plating and most probable number procedures. Nematode-tra
pping fungi detected were Arthrobotrys brochopaga, A. musiformis, A. o
ligospora, A. superba, Geniculifera paucispora, Hirsutella rhossiliens
is, Monacrosporium cionopagum, M. doedycoides, M. eudermatum, M. parvi
collis, Nematoctonus concurrens, and Stylopage sp. A. oligospora was t
he most abundant. Some soil samples contained large numbers of nematod
e-trapping fungi (as many as 695 propagules/g of soil), but sites with
substantial lupine mortality did not contain larger numbers than did
sites with little mortality. In a laboratory bioassay, suppression of
the root-knot nematode Meloidogyne javanica was significant in 44% of
the samples, but suppression was not correlated with fungal population
density; moreover, soil from sites with substantial lupine mortality
was less suppressive than was soil from sites with little mortality. T
he spatial and temporal patterns in fungal abundance and in nematode s
uppression, therefore, did not support our model that nematode-trappin
g fungi cause the patchy distribution of the insect-parasitic nematode
and hence of lupine. Nevertheless, we must be conservative in rejecti
ng the involvement of these fungi in the food chain, because methods f
or fungal quantification have important limitations.