|MadSci Network: Evolution|
A very interesting problem, and unfortunately there really isn't space to do more than point you towards sources of information and evidence.
The first comment you cite is somewhat misleading - and centres around the difference between taxonomy and evolutionary relationships. Whilst most biologists agree that the taxonomy (names and classification of organisms) should reflect the evolutionary relationships between organisms, it is not quite clear how this is best acheived. However, this has few implications for evolutionary theory - widely accepted methods DO exist for determining how organisms are related to each other...
For more basic information about these, and more links, see the University of California Museum of Paleontology's Journey into the World of Cladistics, or the appropriate chapter in any undergrad. evolutionary biology text, my particular favourite is Ridley (1996). For more detailed information see Kitching et al. (1999) or two references available online from the University of Glasgow
De Queiroz and Gauthier are merely pointing out that our knowledge of relationships isn't necessarily ACCURATELY reflected in the taxonomy, and that once we have produced a phylogenetic tree showing the relationships between organisms, there is no single widely accepted method for turning this into a classification.
As for speciation, it is true that our understanding of the process is incomplete, but it seems well established that at least most speciation events result from populations becoming isolated, and subsequent divergence between them and the anbcestral population eventually resulting in reproductive isolation when the populations come back into contact. There is a great deal of pertinent empirical information, again, the best route to finding this is to pick up any of a number of the avaiable undergraduate evolutionary biology textbooks.
Hope this is of some help.
Kitching, I. J., Forey, P. L., Humphries, C. J. and Williams, D. M. 1998. Cladistics, the theory and practice of parsimony analysis, second edition. The Systematics Association Publication No. 11, Oxford Science Publicatioms.
Ridley, M. (1996) Evolution, second edition. Blackwell Science, Inc.
Try the links in the MadSci Library for more information on Evolution.