What is an example of the Allee effect?

One of the most famous examples of a possible Allee effect involves the passenger pigeon (Ectopistes migratorius). The passenger pigeon was one of the most abundant birds in North America. Some estimate that the total species abundance may have been over three billion at one time!

What does the Allee effect describe?

An Allee effect is a positive association between absolute average individual fitness and population size over some finite interval. Such a positive association may (but does not necessarily) give rise to a critical population size below which the population cannot persist (Stephens et al. 1999).

What is the difference between demographic stochasticity and environmental stochasticity?

Abstract. Demographic stochasticity (sampling variation in births and deaths) and environmental stochasticity (effect of random environmental fluctuations on growth rate) in population growth are usually modeled using different approaches.

Is the Allee effect density Dependant?

The Allee effect strictly refers to inverse density dependence at low density. Factors involved in generating inverse density dependence are numerous and have been described for most major animal taxa3. These factors can be classified into three main categories4.

How does stochasticity affect whether a species is found in a certain area?

According to Hanski, species that show high rate of dispersal but low levels of regional stochasticity have a higher chance of long-term survival. It has also been proposed that dispersal is mostly advantageous to a population if patch variation (regional stochasticity) is low.

What causes Allee effect?

In general, these Allee effect mechanisms arise from cooperation or facilitation among individuals in the species. Examples of such cooperative behaviors include better mate finding, environmental conditioning, and group defense against predators.

How does genetic drift affect allele frequencies?

Summary. Unlike natural selection, genetic drift does not depend on an allele’s beneficial or harmful effects. Instead, drift changes allele frequencies purely by chance, as random subsets of individuals (and the gametes of those individuals) are sampled to produce the next generation.

What causes an Allee effect?