What is full form/ meaning of 'r' and 'K' in r-selection species and K-selection species? Does this 'r' means "Random" and the 'K' means "constant"?


2 Answers 2


This article discusses the origin of the terms. They come directly from the equation used to describe population dynamics. As Canadianer mentioned the Wiki also covers it quite well.

"r" stands for "rate" {growth rate}, r strategists have a high r value and a low K value. They grow fast but most die.

"K" stands for Kapazitätsgrenzen which is german for capacity limit, now called carrying capacity, K strategists have a low r and a high K. They grow slow but more survive.

enter image description here

  • $\begingroup$ @Canadianer Thanks for catching that I meant to reverse the terms and then forgot to go back and do it when I started trying to get an equation to import. $\endgroup$
    – John
    Commented Apr 24, 2017 at 20:31
  • $\begingroup$ That should be Kapazitätsgrenze. "Grenze" is the German word for limit/border. $\endgroup$
    – Dunois
    Commented Jun 7, 2019 at 10:48
  • $\begingroup$ Correctly answers my question, and accepted using green tick mark. $\endgroup$
    – user25568
    Commented Sep 4, 2019 at 15:44

If you are looking for a way to understand and remember these letters, because I too found these terms confusing initially, then I use the following.

r-strategy = focus is on Reproduction Rate as much as possible - then all the other traits, grow fast, die young, etc, tend to follow.

K-strategy = focus is on the Kapacity (Germanised spelling) of the environment, i.e. do not exceed the carrying capacity of the local environment for your species.

  • 2
    $\begingroup$ The question is about the origin of these terms. Your answer doesn't seem to address that. $\endgroup$
    Commented Jun 6, 2019 at 8:19
  • $\begingroup$ Upvoted since it may indicate possible etymology but op wasnt finding mnemonic rather op was misleaded where somehow a mnemonic was misinterpreted as a techinical. definition. $\endgroup$
    – user25568
    Commented Sep 4, 2019 at 15:42
  • $\begingroup$ WYSIWYG: The questioner was asking about the etymology, but I think not out of interest in linguistics, but out of a need to (1) understand and (2) remember these terms. When the letter cannot be related to a word (in a language you know), this becomes difficult in both respects. So my response answers the implied need. In any case, my response also contains some etymology. Obviously, making the word Kapacity tells you that this letter comes from the German for Capacity. And R standing for Reproduction Rate surely tells you that that is the etymology/source of the user of that letter? $\endgroup$
    – Comfunc
    Commented Nov 20, 2021 at 18:26

You must log in to answer this question.