Biology Reference
In-Depth Information
Baltic Sea region of Europe and subsequently, in 1982, the North Amer-
ican Great Lakes. It was presumed that this colonization occurred through
ballast water transport, but the proximate source of the North American
invasion was not known. Cristescu et al. (2001) sequenced two mitochon-
drial genes to characterize spiny cladoceran populations in Europe, Asia,
and North America and infer routes of invasion (fig. 4.1). The forms of
the spiny cladoceran in the Black and Caspian seas differed in the haplo-
types represented, so much so that the divergence of these two forms is
estimated to have occurred 800,000 years ago.The Baltic Sea population
showed one DNA haplotype that is among the several that occur in the
Black Sea population. In turn, the Great Lakes population contained only
the haplotype present in the Baltic Sea.
As we noted earlier, another spiny cladoceran,
Bythotrephes longimanus
,
that has invaded North American lakes was determined to have come
Figure 4.1.
Frequencies of haplotypes for populations of the spiny cladoceran
(
Cercopagis pengoi
) in its alien range in North America and in its native range in
Eurasia. These haplotype patterns indicate that the North American Great Lakes
populations came from the Baltic Sea region and that the Baltic Sea population
probably derived from the Black Sea. (Reprinted with permission from M. E. A.
Cristescu, P. D. N. Hebert, J. D. S. Witt, H. J. MacIsaac, and I. A. Grigorovich.
2001. An invasion history for
Cercopagis pengoi
based on mitochondrial gene
sequences.
Limnology and Oceanography
46:224-229. © 2001 American Society of
Limnology and Oceanography.)
