A couple of articles; one newer, one older:

ScienceDaily (Feb. 24, 2009) — The extinction of species is a consequence of their inability to adapt to new environmental conditions, and also of their competition with other species. Besides selection and the appearance of new species, the possibility of adaptation is also one of the driving forces behind evolution. According to the interpretation that has been familiar since Darwin, these processes increase the “fitness” of the species overall, since, of two competing species, only the fittest would survive.

LMU researchers have now simulated the progression of a cyclic competition of three species. It means that each participant is superior to one other species, but will be beaten by a third interaction partner. “In this kind of cyclical concurrence, the weakest species proves the winner almost without exception,” reports Professor Erwin Frey, who headed the study. “The two stronger species, on the other hand, die out, as experiments with bacteria have already shown. Our results are not only a big surprise, they are important to our understanding of evolution of ecosystems and the development of new strategies for the protection of species.”…

This “law of the weakest” even held true when the difference between the competing species was slight. “This result was just as unexpected for us,” reports Frey. “But it shows once more that chance plays a big part in the dynamics of an ecosystem. Incidentally, in experiments that were conducted a couple of years ago on bacterial colonies, in order to study cyclical competition, there was one clear result: The weakest of the three species emerged victorious from the competition.”…

More… (source)

Of course, counterproductive results have never been a problem for evolutionists – it just means that evolution must be even more productive in other areas than was previously thought…

ScienceDaily (Mar. 28, 2008) — The rate at which new species are formed in a group of closely related animals decreases as the total number of different species in that group goes up, according to new research…

Competition between closely related species for food and habitat becomes more intense the more species there are, and researchers believe this could be the reason for the drop-off in the appearance of new species over time…

“In essence, it seems like increased competition between species could place limits on the number of species that evolve.”

The new study used detailed analysis of the family trees, or phylogenies, of 45 different bird families. By examining the rate at which new species have arisen in each of these trees over a period of millions of years, scientists saw that the rate of appearance of new species seemed to be much higher in the early stages of the family tree, compared to more recent lower rates…

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Sounds like this would be another limiting factor, if you take their calculations as accurate. Of course, if you’re taking today’s rates of evolution and comparing them to older presumed rates, you would expect these stated results if progressive evolution doesn’t actually occur. Either way, what is it, now that evolution needs as a driving force? Too much competition equals no evolution and other patterns equal negative evolution. Is evolution supposed to occur only where there is essentially no inter-species competition at all? One thing we can take from these results, however, is that oversimplified models cannot be assumed to describe evolution with very much accuracy.

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