Symbiosis and organismal boundaries

Abstract

The functional boundaries of organisms may not be exclusive or discrete. The genomes of organisms include not only stable genes which replicate faithfully at each division but also transposable elements (jumping genes) and viruses which allow both dynamic variability within a genome and interspecific genetic interactions. All organisms (with the exception of specially maintained laboratory organisms) are in association with other organisms. In close heterospecific associations (symbioses) there are selective advantages for mechanisms which enable organisms to coordinate their activities. In very close, efficient symbioses, mechanisms to share the genetic control of essential, mutually used structures, may have evolved via the activities of movable genetic elements (e.g., transposable elements). Interactions across species boundaries will include examples on the genetic level, cellular level, and organismal level. © 1989 by the American Society of Zoologists.