Question

One of the big issues in ecology today is to explain global patterns of variation in species richness, i.e. why there are more species in the tropics? List (1-4) and briefly describe 4 hypotheses to explain why there are more species in the tropics. Indicate which you think are more important and why.

Answer 1

The important 4 hypothesis that explains why the species are more in the tropics are given below :

1) Species time hypothesis: This hypothesis explains the sprecies richness is depented on time. Species gain ewith evolution or the communities diversity occures over time . Tropics has faster recovery and faster rate of speciation. Tempearte ragions are recently evolbves regions thus reguire much more time for species groethn or richness Tropic region showsmore richness based on the time because this region receives ambient temoerature, shorter generation time and  increased mutation rates.

2) Species area hypothesis:  This hypothesis explains that species richness is influenced by the area. Species richness increases with the increase in areas the area increase . Tropics has higher area so this region shows species richness with larger range and population size. Tropics has more extensive biome with vast and equal range towrds the north and south with uniform sprecies distribution.

3) Species energy hyothesis: This hypothesis indicates energy determines species richness.The increased productivity of the region and there by attaining species richness by the availability of adequate energy is to be high in  tropic region . tropic region is blessed with high solar energy along with water availibility increasing the plant productivity. This increased primary productivity helps in  further growth of herbivores and then omnivores ; thus attaining a high species richness.

4)The intermediate disturbance hypothesis : This hypothesis states that species richness is influenced by the disturbunces caused to the region. Frequency of disderbunces like the occurance of fire, flood etc can drive the specires richness. disturbsances with lower frequency t can cause the dominant speces that are K Selected to outcompete the others and the heavier disturbances influences the r selected organisms to migrate to the safe regions. In tropics the disturbances are of intermediate frequency with not being too hard or light thus the recovery and growth is easily possible in this region improving the species richness.