Fecundity

Fecundity is the physiological maximum potential reproductive output of an individual (usually female) over its lifetime and represents one of the major cornerstones of theoretical and applied population biology. Fertility, a related concept, is defined as the current (actual) reproductive performance of an individual. Many strategies have evolved to shape patterns in fecundity so that lifetime reproductive success (the genetic contribution to the next generation) is maximized under the evolutionary selective pressures experienced by an organism. Fecundity is an important component of both sexual and asexual reproduction, and it can be viewed as a direct (production of offspring) or an indirect (assisting in the reproduction of related individuals) process. Temporal patterns in fecundity fall under two main categories: (1) semelparity - the production of offspring only once during an organism's lifetime and (2) iteroparity - the repeated production of offspring. Factors influencing temporal variation in fecundity and fertility include age, body size (allometric) relationships, the effects of population density, mate choice, and environmental variability. A particularly important framework for understanding fecundity patterns examines the energetic tradeoffs that exist between reproduction and survival, that is, opting to reproduce at the expense of surviving or vice versa. From a genetic perspective, reproductive fitness is the combination of fecundity and survival and is used to measure the effects of inbreeding depression on populations.