Dynamics of a subterranean trophic cascade in space and time

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Date
2008Author
Ram, Karthik
Gruner, Daniel
McLaughlin, John
Preisser, Evan
Strong, Donald
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Trophic cascades, whereby predators indirectly benefit plant biomass by reducing herbivore pressure, form the mechanistic
basis for classical biological control of pest insects. Entomopathogenic nematodes (EPN) are lethal to a variety of insect hosts
with soil-dwelling stages, making them promising biocontrol agents. EPN biological control programs, however, typically fail because
nematodes do not establish, persist and/or recycle over multiple host generations in the field. A variety of factors such as local
abiotic conditions, host quantity and quality, and rates of movement affect the probability of persistence. Here, we review results
from 13 years of study on the biology and ecology of an endemic population of Heterorhabditis marelatus (Rhabditida: Heterorhabditidae)
in a California coastal prairie. In a highly seasonal abiotic environment with intrinsic variation in soils, vegetation structure,
and host availability, natural populations of H. marelatus persisted at high incidence at some but not all sites within our study area.
Through a set of field and lab experiments, we describe mechanisms and hypotheses to understand the persistence of H. marelatus.
We suggest that further ecological study of naturally occurring EPN populations can yield significant insight to improve the practice and management of biological control of soil-dwelling insect pests.