# Reproductive value (population genetics)

(Redirected from Fisher's reproductive value)

Reproductive value is a concept in demography that represents the discounted number of future girl children that will be born to a woman of a specific age. R. A. Fisher first defined reproductive value in his 1930 book The Genetical Theory of Natural Selection. Fisher proposed that future offspring be discounted at the rate of growth of the population; this implies that reproductive value measures the contribution of an individual of a given age to the future growth of the population.

## Definition

Consider a species with a life history table with survival and reproductive parameters given by $\ell_x$ and $m_x$, where

$\ell_x$ = probability of surviving from age 0 to age $x$

and

$m_x$ = average number of offspring produced by an individual of age $x.$

In a population with a discrete set of age classes, Fisher's reproductive value is calculated as

$v_x = \sum_{y=x}^{\infty} \lambda^{-(y-x+1)} \frac{\ell_{y}}{\ell_{x}} m_{y}$

where $\lambda$ is the long-term population growth rate given by the dominant eigenvalue of the Leslie matrix. When age classes are continuous,

$v_x = \int_{x}^{\infty} e^{-r(y-x)} \frac{\ell_{y}}{\ell_{x}} m_{y} dy$

where $r$ is the intrinsic rate of increase or Malthusian growth rate.