Many factors such as latitude, altitude, and the buffering effects of large bodies of water affect climatic conditions, regional differences occur in all biological events. Because of the wide range of variability in climate, scientists look elsewhere to predict natural events. This area of science called Phenology, is an area of science that has received a renewed interest in recent years. It can be defined as the timing of natural living processes with weather events. The return of various migratory songbirds, the blooming of wildflowers and woody landscape plants, and the development of locally indigenous insects are all examples of phenological events which are easily observed each spring in any location. Phenology observes the relationship between 1) discrete phenological events, 2) events and the season, 3) events and local weather conditions, and 4) events and climatic changes. Records of such natural events over a period of several years are helpful in determining climatic changes as well as any shifts in native plant or animal populations (Delahaut).
A host shift may occur when the novel host is phenologically similar to the ancestral host, preadaptations to utilize the novel host exist in the ancestral race, and traits of the novel host alter characters such as emergence times, host preference, or reduction in predation/parasitism/competition. Short generation times and close associations with host plants make it likely that phytophagous insects experience rapid speciation in sympatry by shifts in host-plant utilization and subsequent adaptation to a novel host (Abrahamson & Weis, 1997). Two changes must occur: a genetic change in the host recognition process, and in the traits that affect survival on the new host. Models assume that relatively few genes are required to change for reproductive isolation and speciation. Perhaps only one for preference and one for performance.
Data obtained from...