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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Phylogenetic reconstruction of the tussock moth tribe Nygmiini (Lepidoptera: Lymantriidae) based on morphological characters

Liao, Shih-ruei 24 August 2010 (has links)
The Nygmiini is a tussock moth tribe which is redominantly distributed in most regions of the Old World. It was established in order to accommodate several genera that were previously associated with the polyphyletic genus Euproctis Hübner, 1819, which was erected upon the western European Euproctis chrysorrhoea (Linnaeus, 1758)(=Phalaena chrysorrhoea) and has included 682 valid specific names since the early 19th century. The caterpillars of Nygmiini are fairly polyphagous on various woody plant families, and thus many of them are considered as pests with significant importance. They are also known for having importance in public health due to the strong allergic reaction caused by the urticating setae. Although the tribe Nygmiini as well as the core genus Euproctis has such importance in various aspects, it¡¦s monophyletic status and phylogenetic relationships have never been tested using modern phylogenetic methods. I therefore sampled 175 lymantriid species representing most of the potential members of Nygmiini plus one arctiid species as the outgroup taxon to reconstruct the phylogeny of this tribe based on morphological characters from all development stages. The results suggest that the tribe Orgyiini forms a monophyletic clade with the Nygmiini, while neither the Nygmiini sensu Holloway nor the genus Euproctis sensu auctorum is monophyletic, and thus the taxonomic boundary of the tribe should be redefined in accordance to the hypothesis proposed by the present study. On the other hand, larval characters become the major source of the synapomorphies of the Nygmiini. The adult wing patterns which are used to taxonomic identification, however, are highly convergent among genera and thus these characters are not supposed to be informative in systematic research.
2

Temperature/Development relationships and life history strategies of arctic Gynaephora species (Lepidoptera: Lymantriidae) and their insect parasitoids (Hymenoptera: Ichneumonidae and Diptera: Tachinidae) : with reference to predicted global warming

Morewood, William Dean 06 November 2017 (has links)
Increases in temperature and precipitation predicted under global warming are expected to be most pronounced and thus have their greatest impact on ecosystems at high latitudes. Insects constitute a major component of the foodwebs of terrestrial ecosystems and should be among the first organisms to show noticeable responses to predicted global warming, especially in the Arctic where climatic conditions are often limiting. However, interactions among species must also be taken into account. The genus Gynaephora Hübner (Lepidoptera: Lymantriidae) is represented in North America by two species, G. groenlandica (Wocke) and G. rossii (Curtis), and their geographic distributions overlap broadly across the Canadian Arctic. Previous studies have examined the biology, ecology, and physiology of these two species and have revealed many adaptations to the Arctic environment, but the immature stages of these insects have been misidentified even in recently published reports. Both species are found at Alexandra Fiord, Ellesmere Island, a High Arctic oasis largely isolated by expanses of ocean and icecap, and the population of G. groenlandica at this site is thought to be limited mainly by parasitoid-induced mortality rather than by climatic conditions. Field observations, surveys, and temperature-manipulation experiments were conducted at Alexandra Fiord during the spring and summer of 1994, 1995, and 1996; laboratory rearing was conducted under controlled conditions at the University of Victoria in the spring of 1996 and 1997. Immature stages of both species of Gynaephora were described and illustrated, and all species of insect parasitoids using Gynaephora species as hosts at Alexandra Fiord were identified. Life histories and seasonal phenologies for Gynaephora species and their insect parasitoids were elucidated from field studies, and temperature/development relationships for selected stages of most of these species were derived from laboratory rearing. The results of field studies and laboratory rearing were compared and used to formulate predictions about the responses of these insects to predicted global warming. Immature stages of the two species of Gynaephora are easily distinguished by differences in the colour patterns, form, and overall length of the larval hairs and by the structure of their cocoons. Both species of Gynaephora complete metamorphosis and reproduction within a single growing season but spread larval development over a number of years. In G. groenlandica, seven larval instars and annual moulting combine to produce a seven year life cycle whereas G. rossii develops through six larval instars at a rate of two or three moults per year, resulting in a three or four year life cycle. The parasitoid complex at Alexandra Fiord consists of three primary parasitoids, Hyposoter pectinatus (Thomson) (Hymenoptera: Ichneumonidae), Exorista n.sp. (Diptera: Tachinidae), and Chetogena gelida (Coquillett) (Diptera: Tachinidae), and one hyperparasitoid, Cryptus leechi Mason (Hymenoptera: Ichneumonidae). All of the parasitoids are univoltine, although H. pectinatus may undergo delayed development in some cases, and each of the primary parasitoids relies primarily on a single larval instar for hosts whereas the hyperparasitoid attacks the primary parasitoids during their metamorphosis. Seasonal phenologies of the parasitoids provide optimal access to new hosts but parasitoid-avoidance strategies of Gynaephora larvae ensure that a proportion of their populations escape parasitism. Laboratory rearing showed that the relative timing of host and parasitoid seasonal phenologies is maintained over a broad range of temperatures; therefore, temperature increases predicted under global warming are unlikely to have any great effect on host-parasitoid interactions. However, increased cloudiness associated with the predicted increase in precipitation might have profound effects resulting from lower ground-level temperatures caused by a lack of solar heating. The extent of this effect is uncertain but might lead to reproductive failure in Gynaephora species, with similar repercussions for the insect parasitoids. / Graduate
3

Modelling the proximal source of intercepted exotic insects

Guichard, Sylvain January 2009 (has links)
Biological invasions are major threats to any nation’s economy and biodiversity. To detect new biological incursions of some species biosecurity agencies deploy pheromone sentinel traps for targeted species at high risk sites such as airports, seaports and transitional facilities. A good example is the gypsy moth surveillance program in New Zealand. Following the detection of an incursion by an unwanted organism, ground-based searches to locate the source can be very expensive, but are essential to identify the introduction pathway and to increase the chances of success eradicating the unwanted organism. In such circumstances, the possibility of better targeting the search for the source of the incursion using a modelling approach is worthy of investigation A stochastic mechanistic model to hindcast moth flight from a recapture location to the release location was developed based on insect behaviour in response to wind and pheromones. The model was composed of two main processes, 1) downwind dispersal, assumed to result from an appetitive behaviour, indicated by an analysis of a previous mark-release-recapture experiment on painted apple moth (Teia anartoides, Walker) and, 2) anemotaxic dispersal inspired by pheromone anemotaxis theory but up-scaled from a fine-scaled behaviour model to a 2 m scale. A genetic algorithm was used to fit some model parameters. A specialised fitness function was developed to allow the genetic algorithm to identify parameters that resulted in models that reflected both the spread and density patterns in the trapping data. The resulting function allowed the stochastic model results to be compared with the inherently stochastic trapping data. The resulting individual based model simulates the spatio-temporal dispersal pattern of painted apple moth recorded during a previous mark-release-recapture experiment. While the proposed model is shown to have limitations with respect to accuracy and precision it is also demonstrated to greatly improve biosecurity incursion response capability, by more efficient targeting of search effort for the proximal source of an incursion.

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