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Berg, D. J., D. W. Garton, 1994. Genetic Differentiation in
North American and European populations of the cladoceran Bythotrephes, Ohio
State University, Ohio Sea Grant College Program
Reprinted with permission from Limnol. Oceanogr., 39(7),1994, 1503-1516
with permission of the Americana Society of Limnology and Oceanography, Inc.
Genetic Differentiation in North American and European populations of
the cladoceran Bythotrephes
Abstract:
Bythotrephes cederstroemi, a Palearctic cladoceran (Crustacea) zooplankton, has
recently invaded all of the Laurentian Great Lakes. We used cellulose acetate gel
electrophoresis to examine the genetic structure of these newly founded populations and to
compare it to the structure of established European populations of B. cederstroemi and
a congener, Bythotrephes longimanus. All populations of Bythotrephes had low
intrapopulation genetic variation, with 1-12 multiple-locus genotypes per population.
Genotype frequencies were often different from Hardy-Weinberg expectations for North
American populations, primarily due to heterozygote excesses. Interpopulation variation
was low within drainage basins but high among basins. Great Lakes populations were most
similar to Finnish populations, while Swedish and German populations formed a separate
group. North American populations appear to have been founded from a single European
population, probably located in the northeastern Baltic region. Sympatric populations of B.
cederstroemi and B. longimanus showed a greater degree of similarity than
allopatric conspecifics, leading to the conclusion that these may represent
morphologically distinct forms of a single species. Our results indicate that, as with
other cladoceran species, restricted gene flow and founder events may be important in
determining patterns of geographic variation among populations of Bythotrephes. Genetic
variation among populations within drainage basins was lower than across basins,
regardless of geographic distance between sites. Thus, river basins act as pathways of
dispersal, leading to significant migration between populations within a basin but little
migration between basins.
Entire Paper
Contact: D. W. Garton, Indiana University-Kokomo, 2300 S. Washington Street, P.O.
Box 9003, Kokomo, IN 46904-9003 or
dgarton@iukfsl.iuk.indiana.edu
Keywords: Basic_biology, Bythotrephes, Nonindigenous
Product Type: Research , Basic_biology
User Type: General
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