Chapter 15: Literature: Speciation, Hybridization, and Ecotones
Article SummarySpeciation and Hybridization
Grant, P.R., and B.R. Grant. 1996. Speciation and hybridization in island birds. Philosophical Transactions of the Royal Society of London B Biological Sciences 351: 765-772.
It may be confusing to the scholar of natural selection and evolution to learn about all the details of micro-evolutionary change in Darwin's finches and relate them to each other. Therefore, it is nice to step back from these details for a while and attempt a synopsis of the processes that allow the speciation in island birds, and try to generalize beyond Darwin's finches. This is what Peter and Rosemary Grant did in this publication. The most difficult problem in speciation, in a nutshell, is the problem of how two species are generated from one. There are two alternative models to explain speciation in island birds: allopatry or peripatry (or founder speciation).
The present publication highlights every step during the presumed speciation of Darwin's finches in allopatry and provides background mechanistic data, in order to really evaluate each step of the model. The punch line is: "Differences that evolve in allopatry are reinforced by a regime of divergent selection on the taxa in sympatry arising from ecological pressures and not from reproductive (genetic) incompatibility.... Hybridization potential may last for many million of years after two taxa diverge, implying that post-zygotic isolation evolves slowly."