The three hypotheses for higher species richness in tropical areas are:

(i) Prolong evolutionary time: Temperate areas have undergone frequent glaciation in the past. It killed most of the species. No such disturbance occurred in the tropics where species continued to flourish and evolve undisturbed for millions of years.

(ii) Favourable environment: There are no unfavourable seasons in the tropics. The continued favourable environment has helped tropical organisms to gain more niche specialisation and increased diversity.

(iii) More sunlight: More solar energy is available in the tropics. This promotes higher productivity and increased biodiversity.