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Universal adaptive strategy theory (UAST) is an evolutionary theory developed by
J. Philip Grime
John Philip Grime (30April 193519April 2021) was an ecologist and emeritus professor at the University of Sheffield. He is best known for the universal adaptive strategy theory (UAST) and the twin filter model of community assembly with Simon ...
in collaboration with Simon Pierce describing the general limits to
ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...
and
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
based on the
trade-off that organisms face when the resources they gain from the environment are allocated between either growth, maintenance or regeneration – known as the universal three-way trade-off.
General theory
A universal three-way
trade-off produces
adaptive strategies The expression ''adaptive strategies'' is used by anthropologist Yehudi Cohen to describe a society's system of economic production. Cohen argued that the most important reason for similarities between two (or more) unrelated societies is their p ...
throughout the tree of life, with extreme strategies facilitating the survival of genes via: C (competitive), the survival of the individual using traits that maximize resource acquisition and resource control in consistently productive
niches; S (stress-tolerant), individual survival via maintenance of metabolic performance in variable and unproductive niches; or R (
ruderal), rapid gene propagation via rapid completion of the lifecycle and regeneration in niches where events are frequently lethal to the individual.
It is impossible for an organism to evolve a survival strategy in which all resources are devoted exclusively to one of these investment paths, but relatively extreme strategies exist, with a range of intermediates. The system can be represented by a triangle, with the three extreme possibilities at its vertices. The different species may be located at some particular point inside this triangle, accommodating a certain percentage of each of the three strategies.
It is possible to use multivariate statistics to determine the main trends in
phenotypic variability in a range of organisms, which for various major animal groups (most prominently
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s), has been shown to have three main endpoints consistent with UAST.
UAST is a key part of the twin-filter model describing how species with similar overall strategies but divergent sets of minor traits
coexist
Coexist may refer to:
* ''Coexist'' (album), a 2012 album by The xx
* Coexist (song), 2019 song by Coldrain
* Coexist Foundation, a charitable organization based in London, England
* Coexist (image)
The Coexist image (often styled as "CoeXisT ...
in ecological communities.
C-S-R Triangle theory
C-S-R Triangle theory is the application of UAST to
plant biology
Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...
. The three strategies are competitor, stress tolerator, and ruderal. These strategies each thrive best in a unique combination of either high or low intensities of
stress and
disturbance
Disturbance and its variants may refer to:
Math and science
* Disturbance (ecology), a temporary change in average environmental conditions that causes a pronounced change in an ecosystem
* Disturbance (geology), linear zone of faults and folds ...
.
Competitors
Competitors are plant species that thrive in areas of low intensity stress (moisture deficit) and disturbance and excel in
biological competition
Competition is an interaction between organisms or species in which both require a resource that is in limited supply (such as food, water, or territory). Competition lowers the fitness of both organisms involved since the presence of one of t ...
. These species are able to outcompete other plants by most efficiently tapping into available resources. Competitors do this through a combination of favorable characteristics, including rapid growth rate, high productivity (growth in height, lateral spread, and root mass), and high capacity for
phenotypic plasticity. This last feature allows competitors to be highly flexible in morphology and adjust the allocation of resources throughout the various parts of the plant as needed over the course of the growing season.
Stress tolerators
Stress tolerators are plant species that live in areas of high intensity stress and low intensity disturbance. Species that have adapted this strategy generally have slow growth rates, long-lived leaves, high rates of nutrient retention, and low phenotypic plasticity. Stress tolerators respond to environmental stresses through physiological variability. These species are often found in stressful environments such as alpine or arid habitats, deep shade, nutrient deficient soils, and areas of extreme pH levels.
Ruderals
Ruderals are plant species that prosper in situations of high intensity disturbance and low intensity stress. These species are fast-growing and rapidly complete their life cycles, and generally produce large amounts of seeds. Plants that have adapted this strategy are often found colonizing recently disturbed land, and are often
annuals.
Relation to the R* theory
Understanding the differences between the CSR theory and its major alternative the
R* theory has been a major goal in
community ecology for many years.
Unlike the R* theory that predicts that competitive ability is determined by the ability to grow under low levels of resources, the CSR theory predicts that competitive ability is determined by
relative growth rate and other size related traits. While some experiments supported the R* predictions, other supported the CSR predictions.
The different predictions stem from different assumptions on the
size asymmetry of the competition. The R* theory assumes that competition is size symmetric (i.e. resource exploitation is proportional to individual biomass), the CSR theory assumes that competition is size-asymmetric (i.e. large individuals exploit disproportional higher amounts of resources compared with smaller individuals).
See also
*
Sørensen similarity index Sørensen () is a Danish-Norwegian patronymic surname meaning "son of Søren" (given name equivalent of Severin). , it is the eighth most common surname in Denmark. Immigrants to English-speaking countries often changed the spelling to ''Sorensen'' ...
References
* Grime JP and Pierce S. 2012. ''The Evolutionary Strategies that Shape Ecosystems.'' Wiley-Blackwell, Chichester, UK
* Grime JP. (1979). ''Plant Strategies and Vegetation Processes.'' John Wiley & Sons.
Further reading
*
{{Commons category, C-S-R Triangle
Botany
Ecological theories
Evolutionary biology concepts