Mary Beth Saffo, PhD|
Symbiosis-the intimate association between two or more species-is a surprising biological phenomenon, because the presence, in all organisms, of defense mechanisms against ´┐Żnonself´┐Ż would seem to preclude the persistence of intimate, protracted interspecies associations. Nevertheless, symbiosis is a very common way of life. This paper reviews several examples of this evolutionarily and ecologically important interaction, illustrates some of the complexities of symbiosis dynamics, and introduces some questions and methodological issues of symbiosis research. Five generalizations about symbiotic dynamics are addressed: (1) The evolutionary consequences of symbiosis often defy simple definition. (2) The dynamics of symbiotic interactions change over time. (3) Symbiotic life has a cost. The cost/benefit balance of symbiotic associations can be affected by environmental changes. (4) The most important aspects of interspecies interactions may not be the most obvious ones. (5) Symbiotic interactions reflect both the conflicts and the connections between species individuality and species partnerships.