There are three different hypotheses proposed by scientists for explaining species richness in the tropics. (1) Tropical latitudes receive more solar energy than temperate regions which leads to high productivity and high species diversity. (2) Tropical regions have less seasonal variations and have a more or less constant environment. 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.
Ecologists discovered two broad kinds of diversity patterns, namely:
Latitudinal gradient – This is the most well-defined and well-known pattern of biodiversity studies till date. According to this pattern, the species diversity follows a regular pattern as we move from the equator to the polar regions. The plant and animal diversity are observed to be maximum at the equator and it decreases as we move towards the poles.
Species-Area relationships – The great German geographer and naturalist, Alexander von Humboldt observed the relation between an area and the species richness found in it. He found that as he increased the area of observation, the plant and animal diversity increased but up to a certain level.
