Mountaintop plant communities in central and northern Europe are becoming more species-rich as the warming climate allows lower-altitude plants to move up toward the peaks.If this trend continues,the most likely outcome will be that

A) increasing richness eventually will lower overall community productivity.
B) all species will evolve by partitioning their niches so that a lower but stable diversity level can be maintained.
C) increasing richness will increase competition,which could eliminate some original mountain peak species.
D) one of the new arrivals will eventually drive out all the others,resulting in virtual monocultures on the peaks.
E) the original mountaintop species will move down the mountainsides,increasing the homogeneity of the mountain's plant communities.