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Cascading Chromosomal Speciation in Lizards: A Second Look

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Title:Cascading Chromosomal Speciation in Lizards: A Second Look
Authors:Sites, Jack W Jr.
Thompson, Pamela
Porter, Calvin A.
Date Issued:1988
Publisher:University of Hawaii Press
Citation:Sites JW Jr., Thompson P, Porter CA. 1988. Cascading chromosomal speciation in lizards: a second look. Pac Sci 42(1-2): 89-104.
Abstract:The extent of Robertsonian chromosomal variation in the
iguanid lizard Sceloporus grammicus of Mexico is exceptional among lower
vertebrates, and this case has been the basis for the cascading chromosomal
speciation hypothesis. This paper examines some of the population genetic
assumptions of this model by comparing allozyme variability within and
among 13 samples of S. grammicus with an equal number of samples of the
chromosomally monotypic congener S. graciosus. Only homologous enzyme
loci resolved in both species are used in the comparison. Estimates of such
parameters as mean levels of heterozygosity, average number of alleles per
locus, genetic distances, and F statistics are generally inconsistent with assumptions
of strong population subdivision and/or recent bottlenecks associated
with extinction-colonization events in S. grammicus.. We tentatively conclude
that the population structure of at least some chromosome races in this complex
is sufficiently panmictic to retard the fixation of electromorphic variants.
Problems of making inferences about speciation mechanisms from population
genetic correlates are discussed.
Appears in Collections: Pacific Science Volume 42, Numbers 1-2, 1988

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