Successional changes in a habitat may result in bottlenecks where few individuals in a population survive. During such events, changes in the genetic architecture of traits are predicted to occur as is subsequent inbreeding depression. In two literature reviews, I document that, (1) dominance variance increases in traits that are subject to strong selection and, (2) inbreeding depression is substantially higher in the wild as compared to captive populations. In addition to these changes, successional pressures may also result in the evolution of morphologies that allow organisms to avoid unfavourable conditions. A common dimorphism in insects is wing dimorphism, in which the macropterous morph is long-winged (LW), has functional flight muscles and is flight-capable while the micropterous morph (SW) has reduced wings and cannot fly. Due to the energy required to maintain the flight apparatus, macropterous individuals are predicted to have less energy available for reproduction. Trade-offs to macroptery have been documented in female insects. Gryllus firmus is a wing-dimorphic cricket of the southeastern USA. Although there are well established trade-offs between macroptery and reproduction in female crickets, no trade-offs have been demonstrated in male crickets. The prediction is that LW males, because they have to expend energy to maintain the flight apparatus, will call less and therefore attract fewer females than SW males. To be evolutionarily important, the traits involved in the trade-off; call duration, wing morph, wing muscle condition and lipid weight should have significant heritabilities and be genetically correlated. I found that SW males attracted significantly more females than LW males (mean % = 70% (SW) 30% (LW)). A significant difference in time spent calling was found between SW and LW males and as the difference in calling time between males increased, the likelihood of a female choosing the longer-calling male also increased. All the traits ha
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.34937 |
| Date | January 1998 |
| Creators | Crnokrak, Peter. |
| Contributors | Roff, Derek A. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001641392, proquestno: NQ44396, Theses scanned by UMI/ProQuest. |
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