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  • 1
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Braconidae ; Cotesia marginiventris ; host-finding ; semiochemicals ; conditioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Responses of individual females of the parasitoidCotesia marginiventris to the odors of four different complexes of host larvae feeding on leaves were observed in a four-arm olfactometer. The plant-host complexes were composed of fall armyworm (FAW) larvae or cabbage looper (CL) larvae feeding on either corn or cotton seedlings. Prior to testing, each female was given a brief foraging experience on a plant-host complex and was then exposed to the odors of the same complex in the olfactometer. The experienced females responded to familiar odors in a dose-related manner, and these responses were virtually identical to all four complexes. Preferences for the odors of one of two plant-host complexes were tested in dual choice situations. Generally, FAW odors were preferred over CL odors and corn odors over cotton odors. A short foraging experience significantly affected the females' odor preferences in favor of the odors released by the experienced complex. Additional experiments revealed that neither longer bouts of experience nor bouts that included ovipositions resulted in a stronger change in preference. Experience affected preference in combinations where only the host species was varied as well as in combinations where only the plant species was varied. The results, therefore, strongly indicate that both the plants and the hosts somehow are involved in the production and/or release of the semiochemicals that attractC. marginiventris.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2024-01-12
    Description: After the introduction of Gammarus tigrinus in The Netherlands some 25 years ago and of other recently invading amphipods (Crangonyx pseudogracilis and Corophium curvispinum) the native species decreased, the invaders increased. The success of these invaders and its impact on the local amphipod fauna is discussed. Electrophoretic tests give evidence that a second invasion of Gammarus tigrinus, this time from Germany, is taking place. Some predictions about future developments are made.
    Keywords: Netherlands ; amphipods ; changing distributions ; allozyme electrophoresis ; introduced species ; environmental changes
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
    Publication Date: 2024-01-12
    Description: Genetic differentiation among population samples of G. gauthieri on both sides of the Strait of Gibraltar was investigated by enzyme electrophoresis at 20 enzyme loci with reference to G. gauthieri and G. ibericus from different areas in the Iberian peninsula.\nLevels of divergence resolved suggest that G. gauthieri reached North Africa from the Iberian peninsula, and not vice versa. With reference to geological evidence, this was likely to occur during the Messinian (6\xe2\x80\x945 My ago). As the opening of the Strait of Gibraltar represents a well dated geological event, an attempt has been made to calibrate the molecular clock for the G. pulex-group.\nIndirect estimations of gene flow levels were shown to be extremely low. Probably as a consequence of frequently occurring semi-arid conditions, populations of G. gauthieri are strongly subdivided and likely to be subject to stochastic processes. Therefore, even within areas, population samples may be genetically markedly different.\nDendrograms of genetic distances were compared with geological evidence. From these data an hypothesis of phylogenetic relationships is proposed.
    Keywords: Distribution ; Genetic divergence ; Gene flow ; Molecular clock ; Gammarus
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 4
    Publication Date: 2024-01-12
    Description: Genetic differentiation of morphologically variable members of the G. pulex-group in northwestern Europe was investigated by electrophoresis at 20 enzyme loci. Five recently described related forms were examined with reference to the \xe2\x80\x9cclassical\xe2\x80\x9d species G. pulex, G. wautieri and G. fossarum. G. pulex and G. wautieri were shown to be genetically homogeneous and clearly distinct species. In the other species, morphologically similar forms were shown to be genetically distant, and inter-areal intraspecific genetic differentiation may warrant recognition of subspecies or sibling species. In some cases, levels of reproductive isolation of the forms involved could be assessed by cross-breeding experiments. To estimate dispersal capabilities, gene flow levels were indirectly estimated from gene frequency data. Gene flow levels are generally low and fluctuating population sizes may enhance the occurrence of stochastic processes. Dendrograms derived from genetic distances were compared with zoogeographical and paleoclimatological evidence. The distribution areas of the species involved correspond to patterns predicted by these data.
    Keywords: Taxonomy ; Distribution ; Population structure ; Intra-specific divergence ; Gammarus
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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