Biology Reference
In-Depth Information
3.
Founder Effects and
Exotic Variability
“The initial genetic structure of a successful invasive population
depends on several factors, including the effective size of the introduction
event(s), the genetic diversity of the source population(s), and the number
of founding sources.”
—S
TEPIEN ET AL
. (2002)
The Argentine ant (
Linepithema humile
) is native to South America and
was introduced to the United States in about 1891 in ocean cargo
shipped to New Orleans. It quickly made its way to California, where
it has become a serious pest of agriculture, urban residential areas, and
natural environments. Argentine ants reach very high densities and dis-
place most native ant species, as well as many other ground-living
arthropods. In doing so, they are threatening a specialist ant-feeder, the
coast horned lizard (
Phrynosoma coronatum
). In Argentina, in contrast,
Argentine ants are not nearly as abundant and do not displace other ant
species.
Analysis of the genetics of the introduced populations, using the DNA
microsatellite technique (see below), shows that the three microsatellite
loci examined have only 47% of the variability that is seen in populations
in Argentina (Suarez et al. 1999).The microsatellite alleles present in Cal-
ifornia are also a subset of those noted in Argentina.The frequency of het-
erozygous individuals was about 9% in California, compared to about
30% in Argentina.This clearly indicates that the population introduced in
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