Mechanism and Examples of Allee Effect – Imaluop

Hi, today we are going to discuss mechanism and examples of allee effect, how it works and its examples. We have to understand what is allee effect and how it works. Allee effect gives us a relationship between population size or population density and mean individual fitness.

Allee effects are observed most commonly in sparsely distributed populations. When population density in a region decreases then allee effect becomes very strong on the other hand when population density increases then allee effect becomes weak.

A special phenomenon called the null hypothesis when the population proliferates at a low rate but positive. So the allee effects are completely dependent on critical population size or density of a specific population.

When population growth occurs at a negative rate then the population shows strong allee effect. When a small population shows a decrease in per capita growth rate then it shows a weak allee effect.

When the specific population reaches below the threshold then there is a high chance to become extinct for that population. So we can say that an allee effect shows the relation between the size of the population and the individual fitness within a span of time. The Allee effect shows two manifestations which we will discuss next.

Component Allee Effect: 

A population shows component allee effect when a positive association occurs in some fitness components. 

Demographic Allee Effect: 

Demographic allee effect occurs in a population when component allee effect creates a positive association between population size and per capita population growth.  

Now we will try to understand relations between demographic allee effect and component allee effect. If demographic allee effect is present in a population then it is sure that there must be present the other allee effect component allee effect.

But if component allee effect is present in a population it does not mean that other allee effect demographic allee effect must be present in that population.

For example, the ability to find mates is an example of component allee effect because it affects fitness on the individual of a population.  

Mechanism of Allee Effect: 

Now we will try to understand the mechanism for allee effect which occurs with two factors – survival and reproduction. 

Ecological Mechanism of Allee Effect: 

There are some ecological factors which induce allee effect which we will discuss further. 

Mate Limitations in a Small Size Population: 

In a small population sometimes it becomes very difficult to find the mate for reproduction. For example plants, the phytoplankton and zooplankton present mostly on the surface of water, the sessile vertebrates which are always attached to the button of water bodies face tough challenges to find mates for reproduction. 

Cooperative Feeding Reduce the Chance to Get Food: 

Some species are observed to search for food in a group which makes them unable to get prey sufficiently, especially in case of small size populations. 

Cooperative Defence Mechanism Reduce the Fitness: 

Some species engage to protect themselves against predators, animals in groups which discourage forage and cause reduced individual fitness in a small size population. 

Environmental Conditioning: 

Some species work together to improve their environmental conditions which cause change in biotic and abiotic factors. 

Human Induced Allee Effect: 

When humans start to exploit the rare and valuable species then the species becomes extinct and the value of the species becomes more high. So humans are more attractive towards the rare species than the other common species which leads to allee effect. 

Genetic Mechanism of Allee Effect: 

When population size decreases at a high rate the individual fitness of the population and genetic diversity are lost which cause allee effect. 

Examples of Allee Effect: 

Now we will give some examples of Allee Effect in different taxa. 

Allee Effect in Fruit Flies: 

Fruit flies are a great enemy for most crops because they damage a lot of crops. To control the fruit flies we most often introduce sterile male to reduce them which cause allee effect.

Allee Effect in Fig Trees: 

Allee effect is most common in very low size populations because in low size populations the individual organisms face challenges to find mates for reproduction and fertilization which is observed in fig trees. 

Allee Effect in Rare Organisms: 

Mate finding is really difficult if the members of a population become very few as in case of rare animals and plants which leads to reduced fitness and allee effect. 

Reference: Mechanism and Examples of Allee Effect

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