REINFORCEMENT: A NEW PERSPECTIVE ON AN OLD CONTROVERSY.

A critical component of the reinforcement model, incomplete postzygotic reproductive isolation, has been overlooked in the many selection experiments designed to test this model. Many field observations are consistent with the reinforcement model, but theoretical work predicts that reinforcement should only work when nearly complete postzygotic reproductive isolation has developed. The experiments described here used four levels of postzygotic reproductive isolation: complete, strong, moderate, and none.

De novo synthesis of type-I collagen in bone biopsy material.

A simple and rapid method was established for the cultivation of bone cell tissue. Human bone tissue derived from orthopaedic surgery was cultivated in the presence of 14C-proline and beta-aminopropionitrile. De novo synthesized collagen was extracted from the tissue and quantified by determination of radioactivity in the purified protein.

LABORATORY EXPERIMENTS ON SPECIATION: WHAT HAVE WE LEARNED IN 40 YEARS?

We integrate experimental studies attempting to duplicate all or part of the speciation process under controlled laboratory conditions and ask what general conclusions can be made concerning the major models of speciation. Strong support is found for the evolution of reproductive isolation via pleiotropy and/or genetic hitchhiking with or without allopatry. Little or no support is found for the bottleneck and reinforcement models of speciation.