Which one of the following, if true, most clearly weakens the rate-of-speciation hypothesis as it is described in the passage? A. A remote subgroup of a tropical species is reunited with the original population and proves unable to interbreed with members of this original population. B. Investigation of a small area of a tropical rain forest reveals that many competing species are able to coexist on the same range of resources. C. A correlation between higher energy influx, larger populations and lower probability of local extinction is definitively established. D. Researchers find more undiscovered species during an investigation of an arctic region than they had anticipated. E. Most of the isolated subgroups of mammalian life within a tropical zone are found to experience rapid extinction.