Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
r/K selection theory
open-in-new
<p>In <a href="/facts/Ecology/YE8upuJU">ecology</a>, <i>r</i>/<i>K</i> selection theory relates to the <a href="/facts/Natural_selection/JXTte6en">selection</a> of combinations of <a href="/facts/Trait_(biological)/seYSUTul">traits</a> in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of reduced individual <a href="/facts/Parental_investment/Tbmpk93j">parental investment</a> of <i>r</i>-strategists, or on a reduced quantity of offspring with a corresponding increased parental investment of <i>K</i>-strategists, varies widely, seemingly to promote success in particular environments. The concepts of quantity or quality offspring are sometimes referred to as "cheap" or "expensive", a comment on the expendable nature of the offspring and parental commitment made. The stability of the environment can predict if many expendable offspring are made or if fewer offspring of higher quality would lead to higher reproductive success. An unstable environment would encourage the parent to make many offspring, because the likelihood of all (or the majority) of them surviving to adulthood is slim. In contrast, more stable environments allow parents to confidently invest in one offspring because they are more likely to survive to adulthood. </p><p>The terminology of <i>r</i>/<i>K</i>-selection was coined by the ecologists <a href="/facts/Robert_H._MacArthur/NUQbL6pf">Robert MacArthur</a> and <a href="/facts/E._O._Wilson/YuXAKxp7">E. O. Wilson</a> in 1967 based on their work on <a href="/facts/Island_biogeography/TYCjWgev">island biogeography</a>; although the concept of the evolution of life history strategies has a longer history (see e.g. <a href="/facts/Plant_strategies/MqPEJ8LL">plant strategies</a>). </p><p>The theory was popular in the 1970s and 1980s, when it was used as a <a href="/facts/Heuristic/BcBEkv9c">heuristic</a> device, but lost importance in the early 1990s, when it was criticized by several empirical studies. A <a href="/facts/Life_history_theory/yy5FjMJs">life-history</a> paradigm has replaced the <i>r</i>/<i>K</i> selection paradigm, but continues to incorporate its important themes as a subset of life history theory. Some scientists now prefer to use the terms <i>fast</i> versus <i>slow</i> life history as a replacement for, respectively, <i>r</i> versus <i>K</i> reproductive strategy. </p>