What do you mean by latitudinal gradient? What could be the possible reasons for diversity between tropic and temperate regions?
The latitudinal gradient in diversity means that species diversity usually decreases as we move away from the equator towards the poles. The Tropic area of the latitudinal range 23.50c harbors more species than the temperate or polar area. To explain this difference three hypotheses have been proposed, these are:- i) Speciation is a function of time, which temperate regions were subjected to frequent glaciations in the past, the tropics have to remain unchanged and hence evolved more species diversity. ii) As compared to the temperate region, tropical environments are less seasonal, relatively more constant, and predictable. Niche specialization and greater species diversity have been promoted by such constant environments. ) There is more solar radiation available in the tropical region which contributes directly to greater productivity and indirectly to greater species diversity
