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  • 1
    Electronic Resource
    Electronic Resource
    Genetic flexibility of plant chloroplasts (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 398 (1999), S. 115-116 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The chloroplast genome is thought to be monomorphic, or genetically uniform within individual plants. But a single plant cell may contain several hundred chloroplasts, each containing up to 900 copies of DNA, so there is a huge potential for accumulating and maintaining mutations. I found that ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/18139
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in the electroantennal responses of apple- and hawthorn-infesting races of Rhagoletis pomonella to host fruit volatile compounds (1998)
    Springer
    Chemoecology 8 (1998), S. 175-186 
    Details
    ISSN: 1423-0445
    Keywords: Key words. Rhagoletis pomonella (Diptera: Tephritidae) – apple maggot fly – sympatric speciation – olfaction – host fruit odor – electroantennogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. Domestic apple (Malus pumila)- and hawthorn (Crataegus sp.)-infesting races of Rhagoletis pomonella, Walsh (Diptera: Tephritidae) provide an excellent model to examine the role that host plant specificity plays during sympatric speciation (i.e., divergence in the absence of geographic isolation). Previous work has shown that these races differ in their propensities to accept apple and hawthorn fruits in behavioral choice assays, and that this discrimination translates into "host fidelity" in the field (i.e., apple flies tend to mate on and oviposit into apples and hawthorn flies on hawthorns). ¶We present the results of a study examining possible physiological factors contributing to host choice differences in R. pomonella. We tested whether apple and hawthorn flies differ in their electroantennogram (EAG) responses to biologically relevant volatile compounds emitted from apples and hawthorns. Significant differences were found in the relative EAG responses of apple and hawthorn flies to host fruit compounds at five of six paired study sites across the eastern United States. The geographic pattern of EAG variation was complex, however, with local populations of apple and hawthorn flies tending to be more similar to one another than to flies of the same race at distant sites. This pattern was largely due to EAG responses for several compounds showing longitudinal or latitudinal clines, the latitudinal clines being similar to those observed for allozyme loci in the host races. We also found evidence for sex-related differences, as males tended to have higher mean EAG responses to compounds than females. Host-associated differences were therefore nested within geographic and sex-related differentiation in R. pomonella.¶Further behavioral studies are needed to distinguish whether the EAG differences are responsible for, as opposed to being a consequence of, host-plant fidelity and adaptation. Crosses are also required to establish a genetic basis for the EAG responses, although we did find significant correlations between EAG scores for several compounds and the allozymes NADH-Diaphorase-2 and Hydroxyacid dehydrogenase at one of the study sites. Questions therefore remain concerning the evolutionary significance of the EAG response differences between apple and hawthorn fly races. Nevertheless, these differences raise the possibility that antennal responses to fruit-related volatile compounds contribute to host plant discrimination in R. pomonella. Regardless, the EAG responses represent another set of traits, in addition to diapause/eclosion time phenotypes and allozyme frequencies, differing between apple and hawthorn host races of R. pomonella.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000490050023
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  • 3
    Electronic Resource
    Electronic Resource
    Rhagoletis sibling species and host races differ in host odor recognition (1990)
    Springer
    Entomologia experimentalis et applicata 57 (1990), S. 123-131 
    Details
    ISSN: 1570-7458
    Keywords: Rhagoletis pomonella ; Rhagoletis mendax ; sibling species ; electroantennogram ; host plant odor ; host recognition ; speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Elektroantennogramme (EAG) der Apfel- und der Weissdorn-Wirtsrasse der Apfelfruchtfliege, Rhagoletis pomonella, und der Blaubeerenfruchtfliege, Rhagoletis mendax (Diptera: Tephritidae), wurden aufgezeichnet als Reizantworten auf Wirtsfruchtextrakte und auf neun flüchtige Duftkomponenten ihrer Wirtsfrüchte in sechs Konzentrationen. Die Sensitivität der Antennen bezüglich Apfelduft ist in beiden Arten gleich, aber die Reizantwort von R. mendax auf den Duft ihrer spezifischen Wirtsfrucht, Blaubeeren, ist signifikant stärker als diejenige beider Wirtsrassen von R. pomonella (P〈0.05), was darauf hinweist, dass die antennale Sensitivität möglicherwiese an den artspezifischen Wirtsfruchtduft adaptiert ist. Unterschiede in der antennalen Reizantwort auf mehrere Duftkomponenten der Wirtsfrüchte konnten sowohl zwischen den Arten als auch Wirtsrassen gefunden werden. Dies deutet auf Unterschiede in antennalen Rezeptorzelltypen und/oder Rezeptorzellzahl zwischen Arten und Wirtsrassen. Die Unterschiede wurden von Individuen aufgezeichnet, die keine vorherige Erfahrung mit den Wirtsfrüchten hatten und sind daher genetischen Ursprungs. Fruchtfliegen der Gattung Rhagoletis sind stark wirtsspezifische Pflanzenparasiten, die ihre Wirtspflanze als Treffpunkt und Paarungsort benützen. Diese Resultate deuten daher darauf hin, dass antennale Sensitivität eine wichtige Rolle in Wirtswechseln und Speziation in diesem Genus spielt.
    Notes: Abstract Electronantennograms (EAG) were recorded from the apple and hawthorn host race of the apple maggot fly, Rhagoletis pomonella (Walsh), and from the blueberry maggot fly, R. mendax (Curran) (Diptera: Tephritidae), in response to host fruit extracts and nine volatile host fruit odor compounds at six concentrations. Mean relative EAG response to apple odor is the same in both species, but in respect to blueberry odor, it is significantly stronger in R. mendax than in both host races of R. pomonella (P〈0.05), indicating that antennal sensitivity is selectively adapted to species specific host fruit odors. Differences in antennal response to several host fruit odor compounds were found between both species as well as between the host races. This indicates differences in antennal receptor cell types and/or numbers between species and host races. The flies had no prior host fruit experience which indicates that the measured differences are genetically based. Because Rhagoletis fruit flies are highly host specific parasites which meet and mate on their respective host plants, the results suggest that antennal sensitivity plays an important role in host shifts and speciation in this genus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00343500
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  • 4
    Electronic Resource
    Electronic Resource
    Genetic differentiation and speciation in leaf-mining flies of the genus Phytomyza (1990)
    Springer
    Entomologia experimentalis et applicata 57 (1990), S. 191-200 
    Details
    ISSN: 1570-7458
    Keywords: Phytomyza chaerophylli ; Diptera ; Agromyzidae ; population genetics ; F-statistics ; gene flow ; extinction ; bottleneck ; rapid speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Die Populationsstruktur ist einer der wichtigsten Faktoren, die das Speziationspotential einer Species bestimmen. Wir analysierten die räumliche Variation der Allozymfrequenzen von Phytomyza chaerophylli Kalt. (Diptera: Agromyzidae) nach den Methoden von Wrights F-Statistik. Der Grad der genetischen Variation zwischen den Populationen ist beträchtlich (FST=0.092). Die Variation zwischen lokalen, lediglich durch wenige Kilometer voneinander getrennten Populationen ist gleich gross wie zwischen Populationen, die bis zu 1000 Kilometer auseinander liegen. Eine solche Differenzierung deutet auf einen niedrigen Genfluss zwischen den Populationen. Die Ergebnisse der genetischen Analyse werden gestützt durch ökologische Studien, welche zeigten, dass Wirtspflanzenpopulationen von P. chaerophylli und anderen, nah verwandten Phytomyza-Arten eine inselartige Verbreitung aufweisen und eine verhältnismässig kurze mittlere Lebensdauer haben. Die Populationen von vielen Phytomyza-Arten sind daher meist klein und teilweise isoliert und unterliegen häufig Ausrottungen und genetischen Flaschenhälsen (‘Bottlenecks’). Solche Bedingungen vergrössern beträchtlich die Chance, seltene Mutationen in neuen Populationen zu fixieren, was unter Umständen zu Speziation führen kann. Wir stellen fest, dass Ökologie und Populationsstruktur von P. chaerophylli und anderen Arten dieses Genus günstige Voraussetzungen für eine schnelle Speziation darstellen.
    Notes: Abstract Population structure is one of the most important factors determining speciation potential. We analyzed the spatial variation in allozyme frequencies of Phytomyza chaerophylli Kalt. (Diptera: Agromyzidae) using Wright's F-statistics. The degree of interpopulation variation is substantial (FST=0.092). Variation between local populations separated by only a few kilometers is as high as between populations as far as 1000 kilometers apart, indicating low interpopulation gene flow. The results are supported by ecological studies which revealed that host plant populations of P. chaerophylli, as well as of other, closely related Phytomyza species, are patchily distributed and have a short average life span. Populations of many Phytomyza species are thus mostly small and partly isolated and are prone to frequent extinctions and bottlenecks. Such conditions greatly increase the chance of rare mutations being fixed in new populations which may eventually lead to speciation. It is argued that the ecology and population structure of P. chaerophylli and congeners favor rapid speciation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00343507
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