RECRUITMENT LIMITATION - A THEORETICAL PERSPECTIVE

A theoretical analysis of the concept of recruitment limitation leads to the conclusion that most populations should be regarded as jointly limited by recruitment and interactions between individuals after recr uitment. The open nature of local marine systems does not permit avoid ance of density-dependent interactions; it simply may make them more d ifficult to detect. Local populations consisting of settled organisms may not experience density-dependent interactions under some circumsta nces, but the entire species population consisting of the collection o f local populations and their planktonic larvae must have density-depe ndent dynamics. Any local population of settled individuals can escape density dependence if sufficient density dependence occurs among plan ktonic larvae or within other local populations. Common conceptions of density dependence are too narrow leading too often to the conclusion that it is absent from a system. It is equally wrong to expect that d ensity-dependent interactions after settlement determine local populat ion densities independently of recruitment. Special circumstances allo wing density dependence to act strongly and quickly are needed before density dependence can neutralize the effects of recruitment. Recruitm ent limitation and density-dependent interactions therefore should not be regarded as alternatives but as jointly acting to determine the de nsities of marine benthic populations. Moreover, the interaction betwe en fluctuating recruitment and density dependence is potentially the m ost interesting feature of recruitment limitation. For example, this i nteraction may be an important diversity-maintaining mechanism for mar ine systems.