question_answer 3)

Give three hypotheses for explaining, why tropics show greatest levels of species richness. 

Answer:

(i) Undisturbance in tropics. Speciation is usually a function of time, unlike temperate areas subjected to frequent glaciations in the past. This type of disturbance has not occurred or remained relatively undisturbed in tropical latitudes for millions of years. Tropical regions, thus, got a long evolutionary time for species diversification. (ii) Constancy in season. In tropical regions, environment is more constant, less seasonal and predictable. This is not so in temperate regions. Due to this stability and constancy, niche specialization takes place at a faster rate and leads to species richness. (iii) More solar energy. Due to more availability of solar energy in tropics, productivity is higher. This contributes to greater species diversity, indirectly.