Date of Award
2007
Degree Type
Thesis
Degree Name
Master of Science
Program
Biology
Supervisor
Dr. Jeremy McNeil
Abstract
In insects, migration and reproduction are proposed as alternative strategies, with both being regulated by juvenile hormone (JH). Daylength and temperature are among the environmental cues known to affect JH titres and determine which strategy will be employed. In the model proposed by Rankin and Riddiford (1978) low JH titres are necessary for migratory flight while high levels are associated with sexual development. The fall, southward migration of the monarch conforms to this model, as adults arriving at the overwintering sites are sexually immature and remain so for some months. Much less is known about the underlying physiology of the northward spring migration but the fact that summer immigrants may have high JH titres and are sexually developed, suggest a somewhat different process. 1, therefore, undertook a series of laboratory studies to determine the profile of sexual development, JH biosynthesis and flight capacity of D. plexippus adults reared at 25°C under either short day (12:12 LD) conditions (to reflect those at the start of the northward spring migration) or long day (16:8 LD) ones that are representative of summer conditions in Ontario. The JH biosynthesis and sexual development of field-collected butterflies were also monitored during the summer of 2006. Short day conditions caused a delay in sexual maturation in both sexes and this could provide a window for migration. However, there was not a clear relationship between JH biosynthetic rates and sexual maturation, especially in females. Furthermore, flight performance as a function of age and ecological conditions did not fit with predictions arising from the oogenesis flight syndrome. Alternate explanations for the patterns observed are discussed.
Recommended Citation
Lagace, David, "ECOPHYSIOLOGY OF THE MONARCH BUTTERFLY (DANA US PLEXIPPUS L.) SPRING MIGRATION (Spine Title: ECOPHYSIOLOGY OF THE MONARCH BUTTERFLY)" (2007). Digitized Theses. 5023.
https://ir.lib.uwo.ca/digitizedtheses/5023