Cockroache; Ecology, behavior & history - W.J. Bell

TEN
Ecological Impact
Is there nothing to be said about a cockroach which
is nice?
It must have done a favor for somebody once or twice.
No one will speak up for it in friendly conversations.
Everyone cold-shoulders it except for its relations.
Whenever it is mentioned, people’s faces turn to ice.
Is there nothing to be said about the cockroach
which is nice?
—M.A. Hoberman, “Cockroach”
As a whole, cockroaches are considered garbage collectors in terrestrial ecosystems. They
recycle dead plants, dead animals, and excrement, processes that are critical to a balanced
environment. Here we describe some mechanisms by which cockroaches contribute to
ecosystem functioning via the breakdown of organic matter and the release of nutrients.
We also summarize their ecological impact on numerous floral, faunal, and microbial
components of the habitats in which they live, on a variety of scales ranging from the
strictly local to the global.
DETRITIVORY
Although they are rarely mentioned as such in soil science or ecology texts, the majority
of cockroach species can be classified as soil fauna (Eisenbeis and Wichard, 1985). Many
live in the upper litter horizon, some burrow into the mineral soil layer, and still others
inhabit suspended soils. Cockroaches are also associated with decaying logs and stumps,
rocks, living trees, and macrofungi, which are physically distinct from, but have biological
links to, the soil (Wallwork, 1976). In the majority of these habitats, the core cockroach
diet consists of dead plant material.
Because all species examined to date have endogenous cellulases (Scrivener and Slaytor,
1994b; Lo et al., 2000), cockroaches may act as primary consumers on at least some
portion of ingested plant litter. There is no question, however, that the direct impact of
any higher-level primary consumer does not rate mention when compared to soil microorganisms,
which are universally responsible for breaking down complex carbohydrates
and mineralizing nutrients in plant detritus in all ecosystems. As with other
arthropod decomposers (Wardle, 2002), then, the most profound impact of cockroaches
is indirect, and lies in their complex and multipartite interaction with soil microbes. The
physical boundaries between cockroaches and microbial consortia in soil and plant litter,
however, are not always obvious (Fig. 5.3), and the relationship is so complex as to
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