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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    On Defining Species in Terms of Sterility: Problems and Alternatives
    (University of Hawaii Press, 1988) Paterson, Hugh
    Despite its historic role as a criterion of species status, intersterility sensu lato is not an acceptable characteristic for delineating the genetic species or field of gene recombination. This conclusion is not new since it is in agreement with Darwin 's views as expressed in Origin of Species (1859). The critical role of sterility in distinguishing between the prevailing genetic concept of species and its rival, the recognition concept, is demonstrated. Factors that may have led to the general acceptance of Wallace's views on speciation, rather than Darwin's, are briefly discussed.
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    Evolutionary Relationships of the Hawaiian and North American Telmatogeton (Insecta; Diptera: Chironomidae)
    (University of Hawaii Press, 1988) Newman, Lester J.
    Species of Telmatogeton and the closely related genus Paraclunio generally live on the rocky shores of the intertidal zone. Species of Telmatogeton have evolved from the marine environment into torrential freshwater streams of the Hawaiian Islands . An analysis of the banding sequences of the polytene chromosomes of species of Telmatogeton and Paraclunio from the Hawaiian Islands and North America suggests that there were at least two separate invasions from the marine to freshwater environments. One is through the marine species T. japonicus to an undescribed freshwater species found on east Maui . The other invasion requires a marine hypothetical species that gave rise to the Hawaiian freshwater species T. abnormis and T. torrenticola.
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    Sex Determiners and Speciation in the Genus Chironomus
    (University of Hawaii Press, 1988) Martin, Jon ; Lee, BTO
    In a group of closely related Australian Chironomus species, the position of the sex-determining region is variable, not only in different species (or forms) but , in at least one case, also within the same form. This has raised a number of questions regarding the nature of sex determination and the relevance of variable sex determiners to speciation: (I) Is the sex-determiner location altered by mutation at different steps in a genetic pathway or by translocation (e.g., as a transposable element)? (2) Do polymorphisms for sexdeterminer location exist, or do the apparent polymorphisms result from the existence of cryptic species? (3) Are changes in the location of the functional sex determiner a major component of speciation in this group? This paper considers mainly the third question. A model of speciation involving the sex determiner, compatible with either allopatry or sympatry, is proposed. Comparisons are made with other groups, both invertebrate and vertebrate, which appear to have a similar variable sex-determiner location.
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    Identification of Mullerian Chromosomal Elements in Hawaiian Drosophila by in situ DNA Hybridization
    (University of Hawaii Press, 1988) Jeffery, Duane E. ; Farmer, James L. ; Pliley, Michael
    We have hybridized Drosophila melanogaster DNA sequences to polytene chromosomes of D. silvestris. The results support Muller's hypothesis that the chromosomal elements have been largely conserved in the evolution of the genus Drosophila. As originally suggested by Carson, D. melanogaster elements X, 2L, 2R, 3L, and 3R appear to correspond to chromosomes X, 3, 2, 5, and 4, respectively, in D. silvestris and the Hawaiian picture-winged species.
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    The Role of Heterochromatin in Karyotype Variation Among Hawaiian Picture-Winged Drosophila
    (University of Hawaii Press, 1988) Clayton, Frances E.
    A comparison is made of the amount and distribution of heterochromatin in the mitotic chromosomes of species of the Hawaiian picture-winged Drosophila, and metaphase configurations among these species are compared with those from other regions. Of 103 picture-winged species, only three species (D . melanocephala, D. cyrtoloma, and D. prostopalpis) have any metacentric or submetacentric chromosomes, and only six species have a haploid complement of six acrocentric chromosomes rather than the "primitive" karyotype of five rods and a microchromosome. All karyotype modifications among the picture-winged species can be explained on the basis of modifications in the amount and distribution of heterochromatin; there is no evidence of pericentric inversions or chromosomal fusion.
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