| Popis: |
The cyclic changes associated with seasonal progression probably constitute the most important and all-encompassing set of environmental variables that organisms encounter. Therefore, a fundamental and unifying aspect of each species' or population's life history is the adaptations that determine its seasonal cycle-i.e. the timing of the periods of development, reproduction, dormancy, and migration in relation to seasonal changes in biotic and abiotic factors. Such coordinated sets of seasonal adaptations are popularly referred to as seasonal "strategies." Insects occur all over the world, and they encounter an extraordinary variety and range of seasonal conditions. Although insects that experience similar environmental changes sometimes show similar patterns in their seasonal responses, each species appears to have a unique set of eco-physiological adaptations that underlie its seasonal cycle. Moreover, seasonal adaptations vary within species. This great interand intraspecific diversity in seasonal adaptations subserves the broad geographic distribution of the Insecta and enables insects to utilize diverse, often ephemeral, biotic and abiotic resources and unpredictable habitats. Seasonal cycles also strongly influence interactions between organisms, the major example being the seasonal synchrony between host and parasite (sensu lato). Moreover, in some instances species utilizing a single resource reduce competition by the seasonal partitioning of that resource (e.g. 129). Asynchronous seasonal cycles can also serve as important reproductive isolating mechanisms between both sympatrically and allopatrically derived species (96, 137, 138). Knowledge of the evolution of seasonal cycles thus provides a key to understanding how organisms exploit their environment, how they interact |
