ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Ecological Genetics and Host Adaptation in Herbivorous Insects: The Experimental Study of Evolution in Natural and Agricultural Systems (1990)

Via, S

Palo Alto, Calif. : Annual Reviews

Annual Review of Entomology 35 (1990), S. 421-446

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ISSN: 0066-4170

Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff

Topics: Biology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1146/annurev.en.35.010190.002225

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Variation between strains of the flour beetle Tribolium castaneum in relative performance on five flours (1991)

Via, S.

Springer

Entomologia experimentalis et applicata 60 (1991), S. 173-182

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ISSN: 1570-7458

Keywords: Genetics ; evolution ; host adaptation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract When populations are exposed to different environments, evolutionary processes can lead either to genetically differentiated strains or to the appearance of increased generalism at the individual level. For evolution to occur, genetic variability in performance in different environments is required. Here, intraspecific genetic variation across environments was estimated in the flour beetle Tribolium castaneum (Herbst) by comparing the responses of two strains of T. castaneum to different flour types. Replicated groups from each strain were allowed to develop on either the standard whole wheat medium or on one of four novel flours (wheat, rice, corn and oat). In several of the novel flours, clear differences in mean development time or population size of one or both strains were seen relative to performance in the standard medium. Moreover, the strains differed significantly in their phenotypic responses to the flours. One strain did particularly poorly on oat flour. Reduced oviposition, reduced larval survivorship and increased larval cannibalism were examined as possible causes of the low productivity on oat flour. These three factors accounted for about 70% of the reduction in population size when this strain oviposited and developed in oat flour. The difference between these two outbred strains in response to these five flours suggests that genetic variation in resource use is present within T. castaneum and may also be present within strains and natural populations in grain storage facilities. Such variation would permit an evolutionary response to selection in multiple environments (flours). This process has agricultural implications when several types of grain are stored in a single location because it could eventually lead to the evolution of highly generalized populations of T. castaneum, an important pest of stored products.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00177038

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Inducing the sexual forms and hatching the eggs of pea aphids (1992)

Via, S.

Springer

Entomologia experimentalis et applicata 65 (1992), S. 119-127

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ISSN: 1570-7458

Keywords: Aphididae ; Homoptera ; Acyrthosiphon pisum ; clonal variation ; photoperiod

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract In temperate climates, pea aphids (Acyrthosiphon pisum) produce a single sexual generation each year in response to declining photoperiod and temperature. Mating occurs in the fall and the eggs have an obligatory winter diapause. Genetic recombination during the sexual phase is thought to be an important source of genetic variability within cyclically parthenogenetic aphid populations. Methods for reliably producing sexual forms and hatching the eggs of aphids are therefore central not only to the study of evolutionary change in aphid populations, but also for a general understanding of the origin of agriculturally important variation in destructiveness within pest species. Here, sexual forms of six pea aphid clones were induced in the laboratory and eggs were successfully hatched by creating conditions that closely mimicked those found in field situations. A declining photoperiod was produced by controlling artificial lighting using a timer with variable cycle length. Using these conditions, sexual forms were successfully produced for all six clones tested, which were then mated in all combinations. Eggs were exposed to a daily cycle of freezing and thawing in an incubator under a short-day photoperiod. Egg hatch averaged 60%, but was as high as 89% for some crosses. These methods will permit testing of evolutionary hypotheses and execution of detailed genetic studies of sources of variability within pea aphid populations. They are thus important tools for both evolutionary and agricultural studies.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00221362

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Variation in performance on two grape cultivars within and among populations of grape Phylloxera from wild and cultivated habitats (1994)

Hawthorne, D. J. ; Via, S.

Springer

Entomologia experimentalis et applicata 70 (1994), S. 63-76

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ISSN: 1570-7458

Keywords: Insecta ; pest evolution ; insect resistance ; insect genetics ; demography ; population structure ; insect-plant interactions ; viticulture ; Homoptera ; Daktulosphaira vitifolii

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract When an indigenous insect becomes a pest, comparisons of performance of pest and non-pest populations on crop plants and of genetic variation in that performance may provide insight into the evolution of pest populations. To measure such genetic variation, 8–15 clones of the grape phylloxera (Daktulosphaira vitifoliae Fitch) were collected from wild grapevines in each of 3 geographically isolated sites (populations) and from commercial vineyards in northern California. A complete life table was made for clonal replicates from populations collected from wild grapevines on each of two commercial grape cultivars, the susceptibleVitis vinifera (L.) cultivar Cabernet Sauvignon, and the phylloxera-resistant rootstock ‘AxR # 1’. Variation in mean performance on these two hosts was partitioned among clones within collection sites and among sites. Performance measures included an individual analog to the intrinsic rate of increase (r), age at first oviposition, fecundity in the first ten days of reproduction, total fecundity, and longevity. The overall performance of phylloxera from the wild grapevines on the resistant cultivar AxR # 1 was greater than or equal to that on the susceptible cultivar Cabernet Sauvignon. There was significant variation among clones within populations from wild grapes in the rate of increase on ‘AxR # 1’ and marginally significant clonal variation in some of the component paramters. There was no significant variation among clones within populations on ‘Cabernet Sauvignon’ and no significant differences between populations on either crop in any trait. In a second experiment we compared the relative performance of 15–17 clones from wild grapevines and from commercial vineyards when reared on ‘Cabernet Sauvignon’ and ‘AxR # 1’. Phylloxera from commercial vineyards had much higher overall performance on ‘Cabernet Sauvignon’ than did phylloxera from the wild grapevines. Phylloxera from the commercial vineyard also had higher performance on ‘Cabernet Sauvignon’ than on ‘AxR′ 1’ but the performance of the phylloxera from wild and commercial grapes did not differ on ‘AxR # 1’. Our results show that there is genetic variation in traits related to performance on a resistant rootstock within these indigenous non-pest populations of phylloxera, but not among them. The pattern of performance of pest and non-pest populations on two commercial cultivars suggests that current levels of phylloxera performance on crop cultivars are the result of adaptation to those cultivars which has occurred while phylloxera has been associated with viticulture. Implications of these results for understanding the recent adaptation of phylloxera to ‘AxR # 1’ in California are also discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02380632

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