That is just an abstract. Think of it like a teaser before a movie.
Darwin came up with the theory over a hundred years ago! The beauty of science is the fact that it can be wrong. Science was in its infancy when Darwin came up with the theory, of course there were HUGE gaps. Modern science has greatly improved on his original theory.
Here is the conclusion of the article:
"Although Darwin might have erred in some of the details of his principle of divergence, particularly the generally agreed starting point of reproductively isolated species, his basic idea has merit. The fundamental truth of his principle of divergence has emerged in different facets of evolutionary ecology; a field in which the same principle, in the form of character displacement or some models of sympatric speciation was discovered independently in different contexts over a centrury after the publication of On the Origin of Species. Darwin's linking of extinction to diversification did not re-emerge as the study of extinction rose to prominence in conservation biology. Competitive replacement leading to extinction was once generally and uncritically accepted by palaeontologists before fading into the background after the discovery of mass extinctions. There is compelling evidence, however, of a role for biotic interactions in at least some extinction events and a complementory relationship between divergence and extinction finds enough support for Darwin's proposal to merit further consideration as a viable link between microevolution and macroevolution.
Darwin's Proposal carries a more general message for contemporary discussions of macroevolution, namely that microevolution cannot explain macroevolution. Understanding macroevolution requires the integration of ecology, evolution and the role of history in shaping the diversification or decline of lineages. Other investigators, most recently David Jablonski, have conveyed similar messages."
Here is the full article if you are interested: (it took me some time to dig it up)http://download.bioon.com.cn/upload/201105/17122645_1006.pdf