Should an Organism Produce All of its Offspring at the Same Time or Spread Reproduction Across Years? [1]

Plants and animals use different strategies for ensuring that their offspring will survive to produce more offspring. Evolutionary theory predicts that depending on the relative rates of juvenile and adult survival, an individual should either produce all of its offspring at the same time and then die, or produce a few offspring every year. Species that commonly use the first strategy include salmon; most birds and mammals use the second strategy. Despite a lot of theory that predicts when each strategy should be optimal, few empirical tests exist. This research will use data on rates of survival and reproduction from a number of species that can use both reproductive strategies, depending on environmental factors, to test the theory. A second goal of this project is to explore how these two reproductive strategies affect the persistence of a population when the environment is variable. Understanding a mechanism that can buffer population fluctuations will contribute to predictions of which species may be more vulnerable to increased climate variability.