What is so special about tropics that might account for their greater biological diversity?

@Deepshikha, Akshita has answered correctly.

I would like to add some more points to her answer.

- Tropical environment is less seasonal and almost constant and predictable as compared to temperate environment which support lower extinction rates of species in tropics.

- Greater mean temperature at equator as compared to the poles support survival of more number of species in tropics.

-  Larger areas of tropics can also support larger number of species and also their larger population size.

 - Tropics receive the major part of the solar energy, which contributes to great productivity. Thus, food requirement of more number of organisms are satisfied.

 -Speciation is dependent upon time. Tropical areas have remained undisturbed for millions of years unlike temperate regions, which have experienced frequent glaciations in the past.

Thus, lower rates of species extinction and higher rate of allopatric speciation collectively, also contribute to species richness of tropics.

@Akshita, we really appreciate your contributions to this forum, Keep posting!!