Endophyte: The Evolution of a Term, and Clarification of Its Use and Definition

Abstract

For many terms in biology, giving ironclad definition which is robust over biological time, is like trying to present single, immutable, measurement for the length of the femur bone of horse. You can say how long it is now, and how long is was at different stages in the evolutionary history of the animal, but you probably can not predict what it will be millennium from now. Definitions of many biological terms are the same, they evolve over time. Just as our knowledge evolves, so we change the meaning of terms to better describe what we need to say. This is very apparent when one compares terms in the scientific literature, or the unabridged Oxford dictionary of the English language, from several decades ago, to the meaning we give to the same terms today. So what about the term Endophyte? Wennstrdm (1994) argues that it is abused and misused term to the extent that its use is no longer meaningful. He further suggests that we should either use the term with its original definition, or redefine the term, but argues against the latter. Wennstrdm (1994) used Ainsworth (1971) as example of the original definition and incorrectly stated it as an organism that lives in another organism. Ainsworth (1971) actually defines endophyte as a plant living inside another organism. Endophyte owes its origin to De Barry (1866) who first coined the term. Since then it has become deeply embedded in the literature. Within the last decade, different authors have proposed range of similar, but more complex definitions (e.g., Carroll 1986, Petrini 1991, Wilson 1993). However, endophyte does not stand alone as term whose definition has changed over time, or as term whose definition biologists might not agree over. What about the definition of species? There are probably many definitions of this term. They have changed over time. Darwins concept of species is quite different to the biologists of today, and biologists might not all agree on the concept of species (Moore 1990). But does this make the term meaningless? I would argue that it does not. I will propose useful working definition of endophyte which is meaningful at our current level of understanding about the microorganisms to which we have applied the term. In addition, I will identify areas where the term has been erroneously used as synonym, and show why it is valuable term whose meaning has simply evolved to keep up with our increasing understanding of the biology.