In ecology and biology, a population is a group of individuals of the same species that live in the same geographical area and have the potential to interbreed and produce fertile offspring. Populations can vary greatly in size and can be found in different ecosystems, from a group of deer in a forest to a colony of bacteria in a petri dish. Studying populations allows scientists to understand factors such as population dynamics, growth rates and genetic diversity.
A metapopulation is a concept used to describe a network of local populations of the same species that are connected through occasional immigration and emigration.
A subpopulation, sometimes referred to as a local population, is a smaller, distinct group of individuals within a larger population of the same species. Subpopulations are often separated from each other to some degree, whether by geographical, ecological, or genetic factors. These subpopulations can have their own unique characteristics and dynamics.
Consensus population size (Nc) and effective population size (Ne) are two different concepts in population genetics that describe different aspects of the genetic dynamics of a population:
The consensus population size refers to the actual, observed or counted number of individuals in a population at a given point in time. Consensus population size is typically used in ecological and demographic studies where the aim is to understand the size and structure of a population for conservation or management purposes.
The effective population size (Ne) is a theoretical concept that represents the idealised population size. It quantifies the genetic dynamics of a population. Ne often differs from consensus population size because it takes into account factors such as unequal reproductive success, population structure and other genetic dynamics. It is an essential parameter in population genetics, helping researchers understand how genetic diversity changes over generations and guiding conservation efforts, as it reflects the genetic health of a population more accurately than consensus population size.
Calculating effective population size (Ne) can be a complex process that depends on a number of factors, including the genetic characteristics of the population, its demographic history and reproductive structure. It's therefore not straightforward and often involves simplifying assumptions. The accuracy of the estimate can vary depending on the quality and quantity of (genetic) data, the history of the population and other factors. That's why it's often best done with the help of a population genetics expert or specialised software tools.
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Caballero (1994) Developments in the prediction of effective population size.
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Wang et al. (2016) Review: Prediction and estimation of effective population size.
A famous bottleneck
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