Not having read BN Campbell's Ph. D. thesis, I won't be able to comment on why his analysis failed to resolve relationships. In some cases, the inability to resolve relationships is caused by adaptive radiation, in which taxa diverge very quickly from each other, leaving little time for molecular changes to accumulate. In the case of North American Hyla, this is apparently the case. Several species form an unresolved polytomy when immunological technique was used, suggesting that these species evolved quickly from a single common ancestor and diverged quickly into many different species, ostensibly because of an absence of competition. Hylid frogs originated in the southern hemisphere (Australia and South America) and they did not enter North America until after the collision of the North and South American continents. When a species very similar morphologically to Hyla eximia entered North America, it quickly spread to the entire continent and even to Europe, while diverging into the various species of Hyla, Pseudacris, Acris, and Limaoedus.

The situation in Corallus is not unusal. Similar phenomena are well known even to Darwin. Darwin knows that there are vastly different rates of evolution in different lineages. Darwin has no knowledge of molecular evolution of course, but he and his colleagues are fully aware that the rates of morphological evolution differ widely among different groups of organisms and among different species within the same group. Species which have changed little over vast stretches of geologic time are often called "living fossils." Even within the human lineage, scientists know that the rates of evolutionary change among the apes is much slower than the rate of evolution of the lineage which led to Homo sapiens. Very early on in the development of molecular techniques, systematists realize that the rates of evolution of molecules are very different from the rates of evolution of morphological characters and that the two occur independently of each other. If you compare the mtDNA between human and chimp, the difference is smaller than the mtDNA difference between gorilla and chimp, but the morphological differences are much greater between human and chimp than between gorilla and chimp.

I agree with you that "...phylogenetic analysis only on the base of molecular analysis can lead to wrong hyptheses about the phylogeny of species." The same can also be true of morphological data.

I also agree that weighting can lead to a change in the phylogenetic hypothesis. Weighting is subjective and therefore it depends on how well the researcher understands the molecules with which he/she is working and how well he/she weights his/her characters. By the way, when a researcher treats all characters equally, he/she is also being subjective, since he/she is weighting all characters equally. As for the rejection of data, it can be subjective or objective. If somebody made a mistake in the analysis, such as picking a member of the ingroup as an outgroup, then there is little to do but to reject the data as being unreliable. Such rejection can be objective. If somebody rejects data simply because it contradicts his/her own preconceptions, then it is probably subjective.

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