The Founder Takes All (FTA)

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

refers to the evolutionary advantages conferred to first-arriving lineages in an

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

Overview

Density-dependent processes such as gene surfing, high-density blocking, and competitive exclusion can play crucial roles in the spatial structuring of

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

. These interrelated demographic processes can generate striking geographic contrasts in the distributions of genes and species. Density-dependent processes refer to

biogeographical Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, i ...

processes in which population density (relative to resources) constrains the ability of new arriving lineages to establish It is proposed that well-studied evolutionary and ecological biogeographic patterns of postglacial recolonization, progressive island colonization, microbial sectoring, and even the "Out of Africa" pattern of human expansion are fundamentally similar. All these patterns are underpinned by the "founder takes all" density-dependent principle. For example, following a large-scale earthquake disturbance, two parallel recolonisation events and density-dependent blocking have been hypothesised to explain the occurrence of two distinct spatial sectors of population structure in '' Durvillaea antarctica'' on

Turakirae Head Turakirae Head is a promontory on the southern coast of New Zealand's North Island. It is located at the western end of Palliser Bay, 20 kilometres southeast of Wellington, at the southern end of the Remutaka Range. The head is an excellent ex ...

in New Zealand. It is hypothesized that older historical constraints of density-independent processes are seen today, within the dramatic biogeographic shifts that occur in response to human-mediated extinction events. Due to these extinction events, surviving lineages can rapidly expand their ranges to replace extinct sister taxa.

The FTA model

The FTA model is underpinned by

demographic Demography () is the statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...

and ecological phenomena and processes such as the Allee effect, gene surfing, high-density blocking, and

priority effect In ecology, a priority effect is an impact that a particular species can have on community development due to prior arrival at a site. There are two basic types: An ''inhibitory priority effect'' which occurs when a species that arrives first at ...

s. Early colonizing lineages can reach high densities and thus hinder the success of late-arriving colonizers. It has been suggested that this can strongly influence spatial biodiversity patterns. Scientific evidence for FTA processes has emerged from a variety of evolutionary, biogeographic, and ecological research areas. Examples include: the sectoring patterns sometimes evident in microbial colonies; phylogeographic sectoring of lineages, inferred to have rapidly expanded into new terrain-following

deglaciation Deglaciation is the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice shee ...

; the island progression rule; and sudden biological replacement (lineage turnover) following

extirpation Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...

. One possible scientific consequence of FTA dynamics is that

gene flow In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...

measures based on the genetics of contemporary high-density populations may underestimate actual rates of dispersal and invasion potential.

References

{{reflist Evolutionary ecology

Overview

The FTA model

See also

References