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HOST ASSOCIATIONS, PHENOTYPIC VARIATION, AND MATING COMPATIBILITY OF CHORISTONEURA OCCIDENTALS AND C. RETINIANA (LEPIDOPTERA: TORTRICIDAE) POPULATIONS IN SOUTH-CENTRAL OREGON

Published online by Cambridge University Press:  31 May 2012

W. Jan A. Volney ,
Andrew M. Liebhold  and
William E. Waters
W. Jan A. Volney
Affiliation:
Division of Entomology and Parasitology, University of California, Berkeley 94720
Andrew M. Liebhold
Affiliation:
Division of Entomology and Parasitology, University of California, Berkeley 94720
William E. Waters
Affiliation:
Division of Entomology and Parasitology, University of California, Berkeley 94720
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Abstract

Brown larval morphs, diagnostic of Choristoneura occidentalis Freeman, and green larval morphs, diagnostic of C. retiniana (Walsingham), were found on both Douglas-fir and white fir in mixed stands in south-central Oregon. The rank proportion of brown morphs in stands was strongly correlated with the rank proportion of Douglas-fir in host species basal area component. Despite considerable overlap in most phenotypic characters, differences in phenotypic frequencies between sympatric green and brown morphs were found in larval head capsule pigmentation, thoracic shield pigmentation, pupal coloration, and adult forewing ground color. In laboratory matings, neither larval host nor larval color morph influenced the mating success, as assessed by the production of viable eggs. Crosses between females reared from brown larval morphs and males from green morphs produced a slightly lower proportion of viable eggs when compared with intramorph matings. Larval host had little effect on either the fecundity of females or the viability of their progeny. Females reared from brown larval morphs produced significantly more eggs than their green counterparts from the same stand. The occurrence of intermediates in all mixed stands and the production of families with anomalous morph frequencies indicate that these two species hybridize in nature. The lack of much structural differentiation and varying efficacy of reproductive barriers indicate that relatively little differentiation of the regulatory genome has occurred between these two species.

Résumé

Des larves brunes caractéristiques de Choristoneura occidentalis Freeman et des larves vertes caractéristiques de C. retiniana (Walsingham) ont été trouvées à la fois sur le sapin Douglas et le sapin du Colorado dans des boisés mixtes du centre méridional de l'Oregon. La proportion de larves brunes dans les boisés s'est avérée fortement corrélée à la proportion de Douglas exprimée en termes de surface terrière. Malgré un chevauchement considérable pour la plupart des caractères phénotypiques, des différences sont apparues entre des populations sympatriques des morphes brune et verte pour la pigmentation de la capsule céphalique, la pigmentation de l'écusson thoracique, la coloration pupale et la couleur de fond de l'aile antérieure. Lors d'accouplements en laboratoire, le succès d'accouplement n'a été affecté ni par l'hôte larvaire, ni par la couleur larvaire, tel qu'établi à partir de la production d'oeufs viables. Des croisements entre des femelles obtenues de larves brunes et des mâles provenant de larves vertes ont donné une proportion légèrement inférieure d'oeufs viables, comparés à des croisements intra-morphe. L'hôte larvaire n'a eu que peu d'effets sur la fécondité des femelles ou la viabilité de leur progéniture. Des femelles issues de larves brunes ont produit significativement plus d'oeufs que celles issues de larves vertes provenant du même boisé. La présence d'intermédiaires dans tous les boisés mélangés et la production de familles montrant des fréquences anormales des morphes indiquent que les deux espèces se croisent en nature. L'absence de différenciation structurale substantielle et l'efficacité variable des barrières reproductives montrent qu'il y a eu relativement peu de différenciation du génome régulateur entre ces deux espèces.

Type
Articles
Information
The Canadian Entomologist , Volume 116 , Issue 6 , June 1984 , pp. 813 - 826
Copyright
Copyright © Entomological Society of Canada 1984

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