|SREL Reprint #0540|
Frequency Comparisons Between Sunfish (Centrarchidae) Populations at
Various Stages of Evolutionary Divergence
C. Avise and Michael H. Smith
Avise, J. C. and M. H. Smith (Department of Zoology,
University Georgia, Athens, GA 30602)
1977. Gene frequency comparisons
between sunfish (Centrarchidae) populations at various stages of
evolutionary divergence. Syst. Zool.
26:319-335. – A total of 11-15 genetic loci encoding enzymes and other
proteins has been assayed in populations belonging to 20 taxa of the North
American sunfish in the family Centrarchidea. Four stages of evolutionary divergence are recognized among
these taxa by systematists. We have
determined mean levels of genetic differentiation, D, between populations at
each of these stages: geographic
populations, D= 0.024 + 0.003; subspecies, D = 0.171 + 0.004;
species, D = 0.626 + 0.028; genera, D = 1.340 + 0.064.
D. estimates the number of electrophoretically detectable codon
substitutions per locus accumulated since populations separated from a common
ancestor. Mean genetic distance
among centrarchids increases dramatically through the various stages of
evolutionary divergence. Different
subspecies of Lepomis macrochirus exhibit about an 8-fold increase
in genetic distance over geographic populations belonging to a subspecies. Species of the genus Lepomis are completely distinct
in allelic composition at nearly 50 percent of loci, on the average, despite
their ability to produce viable and sometimes fertile hybrids.
Species belonging to different centrarchid genera have accumulated more
than one allelic substitution per locus, on the average.
Among the centrarchids prezygotic reproductive isolating barriers may
have preceded the development of significant postzygotic isolating mechanisms.
Nonetheless, mean levels of genetic divergence between centrarchid taxa
are similar to those other animal taxa of corresponding rank characterized by
different mode of reproductive isolation. Amounts
and patterns of genetic divergence are employed to infer probably evolutionary
relationships among the Centrarchidae. A
great deal of evolutionary information is contained within even a relatively
small number of genes, [Electrophoresis; genetic distance; sunfish;
SREL Reprint #0540
Avise, J.C. and M.H. Smith. 1977. Gene frequency
comparisons between sunfish (Centrarchidae) populations at
various stages of evolutionary divergence. Systematic Zoology