The effective selfing model is a

mathematical model A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used in the natural sciences (such as physics, ...

that describes the mating system of a

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...

in terms of the degree of

self-fertilisation Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species of ...

present.

Overview

It was developed in the 1980s by Kermit Ritland, as an alternative to the simplistic

mixed mating model The mixed-mating model is a mathematical model that describes the mating system of a plant population in terms of degree of self-fertilisation. It is a fairly simplistic model, employing several simplifying assumptions, most notably the assumption ...

. The mixed mating model assumes that every

fertilisation Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

event may be classed as either self-fertilisation, or

outcrossing Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity. Outcrossing can be a useful ...

with a completely

random In common usage, randomness is the apparent or actual lack of pattern or predictability in events. A random sequence of events, symbols or steps often has no :wikt:order, order and does not follow an intelligible pattern or combination. Ind ...

mate. That is, it assumes that

inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and o ...

is caused solely by self-fertilisation. This assumption is often violated in wild plant populations, where inbreeding may be due to outcrossing between closely related plants. For example, in dense stands, mating often occurs between plants in close proximity; and in plants with short

seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

distances, plants are often closely related to their nearest neighbours. When both these criteria are met, plants will tend to be closely related to the near neighbours with which they mate, resulting in significant inbreeding. In such a scenario, the mixed mating model will attribute all inbreeding to self-fertilisation, and therefore overestimate the extent of self-fertilisation occurring. The effective selfing model takes into account the potential for inbreeding to occur as a result of outcrossing between closely related plants, by considering the extent of kinship between mates. Ultimately, it is not possible to tease apart the two potential causes of inbreeding, and attributed the observed inbreeding to one cause or the other. Therefore, just as with the mixed mating model, in the effective selfing model there is only one parameter to be estimated. However this parameter, termed the effective selfing rate, is often a more accurate measure of the proportion of self-fertilisation than the corresponding parameter in the mixed mating model.

References

Plant sexuality Mating systems Mathematical modeling {{botany-stub