Molecular Ecology Meets Urban Entomology: How Molecular Biology is Changing Urban Pest Management - Urban Insect Pests: Sustainable Management Strategies - page 174

patterns of dispersal and levels of inbreed-
ing, both of which can strongly affect the
spread of pest populations as well as the
spread of insecticide resistance alleles.
Relatively few urban insect pests have been
the subject of studies of population genetic
structure. A large-scale study of the sub-
terranean termite R. fl avipes showed
evidence of some genetic subdivision in
native populations in the eastern USA.
Using microsatellite markers, Perdereau et
al . (2013) identifi ed three genetic clusters,
or populations, within which gene fl ow
appears to be widespread: one population
for nearly the entire east coast from South
Carolina to Delaware (a distance of ~1000
km), one population ranging throughout
Florida and the eastern Gulf Coast (also a
distance of nearly 1000 km), and one
population in southern and western
Louisiana. Thus in this species there seems
to be some large regions in which gene fl ow
is extensive but restricted genetic exchange
between regions. The Mississippi River
appears to divide the Louisiana population
from the Gulf Coast population but there are
no obvious geographic barriers between the
East Coast and Gulf Coast populations.

polygyne form. The two forms are sympatric
in many parts of its range and, interestingly,
sympatric populations of the two social
forms were divergent at their mtDNA
genomes but not their nuclear genomes
(Shoemaker et al. , 2006), presumably
because of male- but not female-mediated
gene-fl ow between the social forms
(Shoemaker and Ross, 1996).
The Argentine ant, L. humile , is well
known for forming large supercolonies in
its introduced range. These colonies can
span distances of hundreds of metres to
thousands of kilometres and are genetically
distinct from other supercolonies toward
which they are highly aggressive (reviewed
in Suarez et al. , 2008). They appear to have
limited dispersal ability on their own and
are mainly spread by human-mediated
jump dispersal, leading to a patchy distri-
bution (Suarez et al. , 2001). Owing to this
mechanism of dispersal, populations show
little genetic structure, i.e. colonies located
further away from each other are no more
genetically differentiated than those closer
together (Tsutsui and Case, 2001). In con-
trast to introduced populations, colonies in
the native range, while also polydomous,
occupy a much smaller area (<100 linear
m). Thus introduced populations differ
from native populations in forming large
supercolonies. One proposed explanation
for this difference between native and
introduced populations is that introduced
populations undergo frequent colony
fusion owing to the impaired ability of
workers to distinguish nestmates from non-
nestmates resulting from genetic
bottlenecks during introduction (Tsutsui et
al. , 2000). Other mechanisms underlying
supercolony formation in introduced
populations have also been proposed
(Giraud et al. , 2002). In the native range,
populations are structured geographically,
with colonies showing a strong pattern of
increasing genetic divergence with
increasing distance (Tsutsui and Case,
2001), suggesting that dispersal in native
populations occurs largely through natural
means rather than the human-mediated
jump dispersal seen in introduced
populations.

Ants

The best-studied species are, with regard to
population genetic structure, the Argentine
ant, L. humile , and the fi re ant, S. invicta . In
the case of the introduced populations of
fi re ants in the USA, genetic studies show
weak differentiation among populations
from Texas to Florida at nuclear markers
(allozymes and microsatellites; F ST = 0.0-
0.08) (Shoemaker et al. , 2006). However,
populations nonetheless formed four
distinct genetic clusters, although these
were much less differentiated than the 10
genetic clusters reported for the native
range (Caldera et al. , 2008). As expected,
the introduced populations showed increas-
ing levels of differentiation with increasing
distance from Mobile, Alabama, the original
site of introduction. The fi re ant occurs in
two social forms (reviewed in Ross and
Keller, 1995): a monogyne form and a