Pacific Science Volume 42, Numbers 1-2, 1988

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Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.

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    Speciation in the Neotropics and the Founder Principle
    (University of Hawaii Press, 1988) do Val, Francisca C.
    The association of bottleneck effects and speciation patterns observed in South American flies Drosophila paulistorum, lizards Anolis chrysolepis and Mabuya arajara, and frogs in the genus Cycloramphus is briefly examined. Bottleneck effects as con sequences of reduction of population sizes in situ seem to be a relevant factor to speciation, distinct from isolation through large-scale fragmentation, environmental differences, or genetic drift.
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    Cascading Chromosomal Speciation in Lizards: A Second Look
    (University of Hawaii Press, 1988) Sites, Jack W Jr. ; Thompson, Pamela ; Porter, Calvin A.
    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.
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    Contrasting Patterns of Differentiation Inferred from Traditional Genetic Markers in the Process of Speciation
    (University of Hawaii Press, 1988) Sene, Fabio Melo ; Pereira, Maria Augusta Querubim Rodrigues ; Vilela, Carlos Ribeiro
    Populations of Drosophila serido from various geographic origins were characterized using four markers: morphology of male genitals, inversions in polytene chromosomes, morphology and heterochromatin of metaphase chromosomes, and reproductive isolation. In all cases the species shows itself to be polytypic, but the geographic distribution patterns vary according to the marker utilized. The validity of the use of these parameters for taxonomic purposes and/or for understanding the mechanisms involved in the differentiation among populations is discussed.
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    Mating Asymmetries and Phylogeny in the Drosophila melanogaster Species Complex
    (University of Hawaii Press, 1988) Robertson, Hugh M.
    The propensities for interspecific courtship and mating among the four species of the Drosophila melanogaster species complex were studied to examine Kaneshiro's hypothesis relating asymmetrical interspecific mating to the direction of phylogeny. Strong asymmetries were revealed, especially involving the ability of sechellia and mauritiana males to inseminate simulans females. A possible basis for these asymmetries involving partial mechanical isolation is proposed. The relationship to phylogeny, if any, remains unclear.
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