Some biologists believe that the latitudinal gradient in species diversity reflects the fact that high latitudes recently lay beneath large glaciers. If there had been no recent ice age, would we still expect to see a latitudinal diversity gradient?

a) No, without polar ice (large ice formation around the pole), warm ocean currents like the Gulf Stream would carry more heat to high latitudes, making them more productive and, so, supporting more diversity.
b) Yes, with or without recent glaciation of high latitudes, there is still less energy available at high latitudes to support diverse biomes.
c) Yes, nutrient availability would still be lower at high latitudes.

The richness of the biodiversity increase as we go form the poles to the topics and find a variety of terrestrial and marine ecosystem and latitudinal biodiversity causes the variation between the rates of the molecular evolution.

Thus there exist a direct relation with the latitudinal extent d the biodiversity of the place and hence the species richness also depends on n this factor as hr available amount of the solar energy and the needed amount of nutrient would be not available to the higher latitude.