allee effect 앨리효과,

뭉치면 좋고, 흩어지면 안좋고 :D

The Allee effect is a phenomenon in biology characterized by 

a correlation between population size or density and the mean individual fitness of a population or species.

(often measured as per capita population growth rate)

The generally accepted definition of Allee effect is positive density dependence, or the positive correlation between population density and individual fitness. 

It is sometimes referred to as "undercrowding" and it is analogous (or even considered synonymous by some) to "depensation" in the field of fishery sciences.

The component Allee effect is the positive relationship between any measurable component of individual fitness and population density. 

The demographic Allee effect is the positive relationship between the overall individual fitness and population density.

The strong Allee effect is a demographic Allee effect with a critical population size or density. 

The weak Allee effect is a demographic Allee effect without a critical population size or density.

Mate limitation

Cooperative defense

Cooperative feeding

Environmental conditioning / habitat alteration

https://en.wikipedia.org/wiki/Allee_effect