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

Abstract

AbstractEmergence 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.