Selective Extinction and Speciation: Their Influence on the Structure and Functioning of Communities and Ecosystems

The structure and functioning of ecosystems can be explained in large part on the basis of the theory of selective extinction as a complement to evolutionary theory. It dates back to A. R. Wallace, and is accepted in principal by many paleontologists. The theory of selective extinction embodies the concept that species are units which are subject to differential or selective failure resulting in extinction. The probability of extinction differs among species, because it is dependent, in large part, on the characteristics of species rather than being a totally random process. Similarly the rates at which new species are produced are nonrandom and depend, in part, upon the nature of the species; some types undergo speciation more readily than others. Patterns such as the abundance of r-selected species relative to K-selected species are thus a result of the balance struck between the rates of extinction and speciation, each of which varies along the continuum of life history traits. In similar fashion, the theory of selective extinction provides a common, although not singular, explanation for such things as the common occurrence of sexual reproduction and the patterns observed in species diversity as related to habitat size (e.g., island size). Although a few ecologists accept the paradigm of selective extinction (and some, such as those involved in island biogeographic work, actually apply it), ecological thinking is in need of more interdisciplinary exchange with paleontological work. Resistance to the incorporation of selective extinction theory in ecological work needs to be overcome by the realization that the theory of evolution and the theory of selective extinction are complementary rather than competitive. Finally, we do not imply in any of our discussion that the effects of selective extinction offer the only explanation for patterns observed in nature. Rather, our emphasis is that selective extinction, synergistically or antagonistically interacts with many other processes to produce community and ecosystem patterns.