Evol Ecol Res 8: 1077-1086 (2006)     Full PDF if your library subscribes.

Measured sanctions: legume hosts detect quantitative variation in rhizobium cooperation and punish accordingly

E. Toby Kiers,1,2* Robert A. Rousseau1 and R. Ford Denison1,3

1Department of Agronomy and Range Science, University of California, Davis, CA 95616,  2Department of Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003-5810 and  3Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55108, USA

Address all correspondence to Toby Kiers, Department of Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003-5810, USA.
e-mail: etkiers@bio.umass.edu


Question: Does severity of punishment vary quantitatively with partner cooperation?

Hypothesis: Sanctions against defecting partners may be crucial for the evolutionary persistence of cooperation. Legume sanctions have been demonstrated when rhizobia either fully defect or fully cooperate, but not when they invest at an intermediate level. We predicted that intermediate rates of cooperation would trigger intermediate sanctions.

Model system: We varied rhizobium cooperation and its importance to the plant by adjusting N2 concentration, manipulating rhizobia to fix N2 at about 1%, 17%, 33%, 50%, and 100% of their potential, and/or by adding nitrate.

Results: Fixation and rhizobium fitness were significantly correlated in a regression model suggesting that sanction strength varies with N2 fixation. Sanction severity was increased by the addition of external nitrate.

Keywords: cheat, cooperation, investment, legume, mutualism, nitrogen fixation, punish, sanction, strategy, symbiosis.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2006 Toby Kiers. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.