r and K Selection or b and d Selection?

  title={r and K Selection or b and d Selection?},
  author={Eric R. Pianka},
  journal={The American Naturalist},
  pages={581 - 588}
  • E. Pianka
  • Published 1 September 1972
  • Psychology
  • The American Naturalist
The concepts of r and K selection and b and d selection are discussed and compared. The former pair of concepts will play a central role in the development of new theories in population biology which relax the assumptions that communities (and portions thereof) are either fully saturated or completely unsaturated. It is hypothesized that maximal tolerable niche overlap should vary inversely with the level of competition, and a test is suggested. 
The meanings of r- and K-selection
This paper catalogues several different dichotomies that have all been termed r- and K-selection and recommends a more restricted usage of the terms.
Selection and the r/K Continuum in Experimental Populations of Protozoa
Study results support the essential prediction that greater competitive ability is compatible only with reduced rates of growth, while poor competitors should have high growth rates.
K-selection, α-selection, effectiveness, and tolerance in competition: Density-dependent selection revisited
This work shows that incorporating notions of α-selection, and the division of competitive ability into effectiveness and tolerance components, into the concept of density-dependent selection yields a formulation that allows for a better understanding of the empirical results, and predicts that selection for faster development in Drosophila should lead to the correlated evolution of decreased competitive ability.
Temporally Dynamic Reproductive Strategies and the Concept of R- and K-Selection
Failure to consider dynamic strategies in reproductive effort associated with environmental changes can result in misleading comparisons of populations and in incorrect interpretations of life-history strategies and corresponding selective pressures.
r-and K-selection in soil ciliates: a field and experimental approach
The results imply that the Colpodea are more r-selected as compared with the Polyhymenophora, which might be an explanation for their wide distribution and high density in unfavourable terrestrial habitats.
It is argued that rand K-selection may have important ramifications for the understanding of life history evolution, but for the model to be useful, it must be interpreted strictly as it was originally formulated: as a model of density-dependent natural selection.
Plant Pathogens and the Theory of r- and K-Selection
A conceptual model is proposed to show how pathogens can be positioned along an r-K continuum based on their relative allocation of resources to maintenance, growth, and reproduction.
Succession of r and K Strategists in Parasitoids
The concept of r and K strategems and their development during the evolution of organisms is certainly not new, although these particular terms to describe the process have been used for only a short


The Concept of r- and K-Selection: Evidence from Wild Flowers and Some Theoretical Considerations
The crucial evidence needed for r- and K-selection is whether an organism is allocating a greater proportion of its resources to reproductive activities than another related one (K-strategist) under any and all D.I. mortality conditions.
Natural selection and the parameters of population growth.
It is concluded that evolutionary reductions in r are most likely to have occurred under density dependence conditions.
Age-Specific Selection. II. The Interaction between r and K during Population Growth
The interplay between density-independent (r) and density-dependent (K) components of selection is investigated using models of Mendelian populations with breeding at discrete intervals and overlapping generations to investigate the effects of environmental variation on the interaction between r- and K-selection.
Selection in Density‐Regulated Populations
It is shown that the eventual outcome of selection is determined by the genotypic K—values, but that the r—values influence the composition of equilibrium populations.
Intrinsic Rates of Increase, Saturation Densities, and Competitive Ability. I. An Experiment with Paramecium
In a set of experiments with pure and mixed cultures of two species of Paramecium "aurelia," it was found that there was no consistent relationship between r and K and competitive success, and that
On the Measurement of Niche Breadth and Overlap.
It is proposed that the species composition of communities utilizing different resource states may be used to develop weighting factors with which each state may be weighted in proportion to its degree of distinctness.
The Community Matrix and the Number of Species in a Community
The number of species that will be held in stable equilibrium in a community of competing organisms, using the general form of the Lotka-Volterra competition equations for m species, is concerned.
Life Historical Consequences of Natural Selection
The tremendous variation in the life-history patterns of organisms is best explained as adaptive, and a model of life history processes has been developed on the basis of these considerations, leading to the following predictions.
Density‐Dependent Natural Selection
A mathematical technique developed for analyzing evolution in coarse—grained seasonal environments reveals genetic mechanisms, including ones with full dominance, with which a moderately harsh seasonal environment causes stable polymorphism between high—r and high—K genes.
The Population Consequences of Life History Phenomena
  • L. C. Cole
  • Economics
    The Quarterly Review of Biology
  • 1954
The part of Cole’s article included here outlines the relationship of Thompson’s work (1931, paper 20 above) to stable population theory. Omitted sections discuss the relationships between the rate