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POST-DIAPAUSE DEVELOPMENT OF SYMPATRIC CHORISTONEURA OCCIDENTALIS AND C. RETINIANA (LEPIDOPTERA: TORTRICIDAE) AND THEIR HYBRIDS

Published online by Cambridge University Press:  31 May 2012

W. Jan A. Volney
Affiliation:
Department of Entomological Sciences, University of California, Berkeley, California, USA 94720
Andrew M. Liebhold
Affiliation:
Department of Entomological Sciences, University of California, Berkeley, California, USA 94720

Abstract

Emergence from hibernacula of 2nd instars of Choristoneura occidentalis was more variable but later than that of C. retiniana. However, early-instar development was faster in C. occidentalis and compensated for the difference in emergence times so that both species entered the 6th instar simultaneously. There were no species-related differences in development beyond the 6th instar. Though they have different resource-tracking patterns early in their life cycle, temporal isolation between these species is unlikely. No developmental morphs were found in either species but there were several instances where individuals that developed at an increased (or decreased) rate in one stage developed slower (or faster) than the mean rate in a substantial stage. Negative correlations between development times were indicative of this. These correlations reduced variation in adult eclosion times induced by extended spring emergence and are indicative of homeostasis in development within populations. Negative correlation coefficients between development periods were more common in C. occidentalis, which also had the more variable spring-emergence pattern. Hybrids were intermediate in almost all development traits.

Résumé

L'émergence des hibernacles des Choristoneura occidentalis de stade 2 s'est avérée plus variable mais plus tardive que celle de C. retiniana. Cependant, le développement des stades initiaux a été plus rapide chez C. occidentalis, compensant ainsi pour la disparité du temps d'émergence, de sorte que les deux espèces sont parvenues au 6ième stade simultanément. On a noté aucune différence dans le développement des deux espèces après le 6ième stade. Quoique ces deux espèces montrent différentes stratégies de poursuite de leurs ressources au début de leur cycle vital, leur isolation temporelle est improbable. On n'a pas observé de morphe en rapport avec le type de développement chez aucune des deux espèces, mais on a noté plusieurs cas d'individus qui, s'étant développés plus rapidement (ou lentement) à un stade donné, se sont développé plus lentement (ou rapidement) que la moyenne au stade suivant. Ceci était indiqué par des corrélations négatives entre les durées de développement. Ces corrélations ont réduit la variation du temps d'émergence des adultes, indiquant l'existence d'homéostasie du développement au sein des populations. Ces corrélations négatives entre les durées de développement étaient plus communes chez C. occidentalis qui montrait aussi la variabilité la plus grande de l'émergence printannière. Les hybrides se sont avérés intermédiaires pour la plupart des traits du développement.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1985

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