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A GEOGRAPHICAL CLINE IN EGG WEIGHTS IN CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE) AND ITS SIGNIFICANCE IN POPULATION DYNAMICS

Published online by Cambridge University Press:  31 May 2012

G. T. Harvey
G. T. Harvey
Affiliation:
Canadian Forestry Service, Great Lakes Forest Research Centre, Sault Ste. Marie, Ontario P6A 5M7
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Abstract

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The mean weights of the initial eggs (Ei) of the spruce budworm, Choristoneura fumiferana (Clem.), vary within and between populations. Measurements of collections from across the range of this species reveal the presence of a cline directly related to latitude and longitude of the collection source. Collection mean Ei values range from 0.219 mg in the northwest to 0.157 mg in the southeast. A similar cline, also related to latitude but negative in slope, is demonstrated for the number of eggs per unit pupal weight. This cline also finds expression in changing slope of fecundity/pupal weight regressions. The cline in egg weight appears to be an adaptation to winter conditions across the range of this insect and should be considered in population dynamics.

Résumé

Le poids moyen des premiers oeufs (Ei) de la tordeuse des bourgeons de l'épinette, Choristoneura fumiferana (Clem.), varie à l'intérieur des populations et d'une population à l'autre. Des mesures effectuées sur des prélèvements provenant de l'ensemble du domaine de l'espèce révèlent la présence d'un cline directement relié à la latitude et à la longitude du point de prélèvement. Les valeurs moyennes de Ei varient de 0.219 mg dans le nord-ouest à 0.157 mg dans le sud-est. On démontre également l'existence d'un cline semblable, également relié à la latitude mais à pente négative, pour le nombre d'oeufs par unité de poids de la chrysalide. Ce cline s'exprime également en changeant la pente des régressions de la fécondité en fonction du poids des chrysalides. Le cline du poids des oeufs semble une adaptation aux différentes conditions hivernales dans le domaine de l'insecte et devrait être pris en considération dans la dynamique de ses populations.

Type
Articles
Information
The Canadian Entomologist , Volume 115 , Issue 9 , September 1983 , pp. 1103 - 1108
Copyright
Copyright © Entomological Society of Canada 1983

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