Introduction

The Reproductive Value ($V_x$) is a measure of the expected reproductive contribution of an individual of age $x$ to the next generation. Thus, $V_x$ is closely tied to the organism’s fitness. The value of $V_x$ is determined by the pattern of age specific changes in the birth rate and the death rate. The reproductive value changes over the course of the life span because the age-specific survival and birth rates determine the number of offspring expected in the future. So, for example, if there is high juvenile mortality, $V_x$ will be lower for young individuals—they must survive the early ages to contribute births. However, once an individual survives that early mortality, its reproductive value increases. Thus, $V_x$ often increases with age to a maximum just as the organism enters the reproductive years. As the birth rate declines with age and survivorship begins to drop, $V_x$ declines as well (see Figure 10.3, on the next page).

Learning Goals

After reading your text and completing this exercise, you should be able to:

• Understand the relationship between Reproductive Value and life table data.
• Understand how changes in the age-specific birth and death rates affect the value of $V_x$.
• Understand how the value of $V_x$ changes over the course of the lifespan.