Question

5) What is the observed latitudinal gradient of biodiversity? Define three hypotheses that explain the latitudinal gradient.

Answer 1

Ans . Latitudinal gradients of biodiversity are biogeographic patterns that quantify the ways in which taxonomic, phylogenetic, functional, genetic, or phenetic biodiversity change with latitudinal position on the surface of the earth.

Species richness or biodiversity, increases from the poles to the tropics for a wide variety of terrestrial and marine organisms, often referred to as the lattitudinal diversity gradient . The lattitudinal diversity gradient is one of the most widely recognized patterns in ecology.

The 3 hypothesis that explain the latitudinal gradient are :-

1) Geographical area hypothesis :- It asserts that the tropics are the largest biome and that large tropical areas can support more species. More area in the tropics allows species to have larger ranges and consequently larger population sizes. Thus, species with larger ranges are likely to have lower extinction rates.

Additionally , species with larger ranges may be more likely to undergo allopatric speciation, which would increase rates of speciation.The combination of lower extinction rates and high rates of speciation leads to the high levels of species richness in the tropics.

2) Species - energy hypothesis :- It suggests the amount of available energy sets limits to the richness of the system. Thus, increased solar energy (with an abundance of water ) at low latitudes causes increased net primary productivity. This hypothesis proposes the higher the net primary productivity the more indivuals can be supported, and the more species there will be in an area.

3) Climate stability hypothesis : It suggests that while a fluctuating environment may increase the extinction rate or preclude specialization, a constant environment can allow species to specialize on predictable resources, allowing them to have narrower niches and facilitating speciation.