Biology Reference
In-Depth Information
from one or more locations between Buenos Aires and Rosario. As we
noted in chapter 3, the genetic impoverishment of these introduced ants
has played a major role in their impact.
Similarly, the regional origin and native plant hosts of grape phyllox-
era ( Daktulosphaira vitafoliae ), an aphid pest of cultivated grapes worldwide,
have been pinpointed by mtDNA analysis (Downie 2002). In Europe,
grape phylloxera is derived entirely from aphids native to the frost grape
( Vitis riparia ) of the northeastern United States.This genetic race of aphids
has also been introduced to several other world regions where grapes are
grown. A second source of phylloxera aphids is the winter grape ( Vitis
vulpina ) of the southeastern United States.This form was apparently intro-
duced to California and from there to Australia, New Zealand, and Peru.
Vectors of human disease also can be traced to their regions of origin.
The Asian tiger mosquito ( Aedes albopictus ) is a recent colonist of the New
World. This mosquito is a vector for various viral diseases, including
dengue fever. Analyses of mtDNA from the United States indicated that
tiger mosquitoes were very similar to those of eastern Asia, including
Japan (Birungi and Munstermann 2002). Other evidence suggested that
tiger mosquitoes arrived in the United States as larvae in pockets of water
in automobile tires shipped from Japan. Asian tiger mosquitoes appeared
soon afterward in Brazil.The mtDNA haplotypes predominant in Brazil,
however, are quite different from those in both the United States and
Japan, so the precise origin of the Brazilian populations is still uncertain.
The origins of some disjunct mammalian populations have been
traced by means of mtDNA analysis.The common vole ( Microtus arvalis ),
for example, occurs on the Orkney Islands, which lie north of the north-
ern tip of mainland Scotland, but not in the rest of the British Isles. The
species is widespread in mainland Europe, and the closest population is in
Denmark. To investigate the precise source area of voles, tissue samples
were obtained from animals from the Orkney Islands and from 26 local-
ities throughout the range of the species in mainland Eurasia (Haynes et
al. 2003). Mitochondrial DNA was extracted from these samples, and the
cytochrome b gene was amplified and sequenced. Numerous haplotypes
were found, but the greatest similarity was between haplotypes of voles
from the Orkney Islands and those from France and Spain. Since the
Orkney Islands were covered by ice during the last glaciation, voles must
have been introduced following glacial retreat. Apparently, the common
vole was brought to the islands by Neolithic human settlers from south-
western Europe, a conclusion that perhaps sheds light on the origin of the
early human settlers of these islands.
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