Agriculture Reference
In-Depth Information
single building than between separate
buildings of an apartment complex. Simi-
larly, neighbour-joining tree and Bayesian
clustering analyses were able to cluster only
those apartments that were within a single
building, indicating higher dispersal with
associated gene fl ow within buildings than
between them. The lack of any broader
connectivity, as indicated by signifi cant
F
ST
s, suggests that human-mediated dis-
persal of
B. germanica
between buildings of
an apartment complex or between com-
plexes occurs infrequently enough to have
negligible effects on gene fl ow.
Obviously there is a need for many more
studies of the population genetic structure
of urban pests. On the basis of the results
obtained so far, the following general
patterns have emerged: (i) species that
primarily inhabit the exterior environment
and have strong inherent dispersal abilities,
such as fi re ants and subterranean termites,
show less genetic structure over small
spatial scales of 10-100 km than do outside
inhabiting species with poor dispersal
ability, e.g. Argentine ants; and (ii) domestic
species that are largely limited to the
interior of human structures show strong
genetic structure on small spatial scales,
even among different buildings within a
city.
tools for identifying species and char-
acterizing populations, genetic methods are
shedding new light on urban insect
development and reproduction, revealing
potential new targets for control. New
targets could include physiological pro-
cesses in the insects themselves using RNAi
technology (Price and Gatehouse, 2008), or
the symbiotic gut fauna that are critical in
lignocellulose digestion in the case of
termites. For example, Zhou
et al
. (2006)
have shown that a hexamerin gene plays a
critical role in soldier determination and
silencing of this gene by application of
RNAi inhibits soldier differentiation.
Targeting this gene or other genes involved
in development or reproduction could offer
a highly specifi c and environmentally
sound way to control termites in the future.
In ants, RNAi has been used to successfully
knockdown expression of the pheromone-
biosynthesis-activating neuropeptide result-
ing in high mortality of workers, pupae and
larvae (Choi
et al.
, 2012). And silencing the
vitellogenin receptor gene through RNAi
inhibited egg laying in fi re ant queens (Lu
et al.
, 2009). The availability of a sequenced
genome for many ants, including some pest
species, such as the fi re ant
S. invicta
(Wurm
et al.
, 2011) and the Argentine ant (Smith
et
al.
, 2011), will certainly provide an un-
precedented view into the fi ne workings
underlying the development, reproduction,
behaviour and physiology of these import-
ant pests and possibility reveal many targets
for control. Genomes of other pest groups,
such as termites (Terrapon
et al
., in press)
and bed bugs (Palli
et al
., unpublished data)
are near completion and should be available
soon, providing new opportunities for
control of these pests. In addition to
targeting the gene of the pest species
regulating physiology and behaviour,
associative behaviour of termites with
symbiotic communities of bacterial fl ora
and protozoans could also be exploited as
potential shuttle systems for delivering
genetic or other control methods to entire
colonies. Husseneder and Grace (2005) have
transformed naturally occurring bacteria
from the gut of
C. formosanus
and
successfully re-introduced them into ter-
Conclusion and Future
Developments
We can expect genetic methods to play an
increasingly important role in urban pest
management in the future. There will
undoubtedly be many contributions in the
areas of taxonomy and tracking the spread
of invasive species. The use of genetic
fi ngerprinting methods to track colonies of
ants and termites will become commonplace
as genotyping techniques become easier
and cheaper. This will greatly advance our
understanding of the colony-level effects of
fi eld treatments, as well as giving us a more
accurate picture of the foraging sizes of
colonies of various species and their popu-
lation densities in different geographic
regions. In addition to providing powerful
Search WWH ::
Custom Search