There are three different hypothesis given by scientist for explaining to show the greatest level of species richness.1) The tropical region has less seasonal variations, and almost constant temperature promotes the specialization, thus, high species richness.2) In the tropical region, more availability of solar energy. This promotes the niche specialization and thus, high species richness.3) Temperate regions were subjected to glaciations during the ice age, while tropical regions remained undisturbed which led to an increase in the species diversity in this region.