Why are there so many rare species?
According to the theory of frozen plasticity, representatives of the old, macroevolutionarily frozen, microevolutionarily elastic species that are kept out of their original state by natural selection, have lowered fitness (viability or fertility) in comparison with representatives of young species living under conditions similar to those existing at the time of their origin. Therefore, statistically, the population density of a species probably negatively correlates with species age; a study of the correlation of the molecular age of species with their average abundance could easily test this prediction. This could also explain the existence of the most universal ecological law – that every community shows a concave curve on a histogram with many rare species and just a few common species. The position of a species on the histogram is rather stable; species retain their basic status as common or rare for as long as one million years. The frozen plasticity theory predicts that the common species are the young species which are still evolutionarily plastic or which have only recently lost their plasticity and are therefore still adapted to current environmental conditions.