Species richness varies between different areas at both regional and global scales. Outline four explanations for variation in species richness between different communities.. Ecology

  1. Evolutionary Speed - the amount of time something has been in existence and the speed at which it evolved will affect the species richness in an area. For example the tropics have a higher species richness because they have been there longer
  2. Geographic Area - the larger the area the more species it can hold. For example the tropics have a large area, therefore can support more species richness
  3. Interspecific Interactions - competition and predation can control the diversity in an area. Competition affects niche partitioning and competition retards competitive exclusion.
  4. Ambient Energy - the higher the input of energy, the higher the species richness. This more solar radiation, temperature and water, the higher the species richness. Fewer species can survive in physically unfavourable conditions. This is another reason why there is more species richness in the tropics.
  5. Productivity - the higher the productivity or energy available, the higher the species richness. Tropical habitats are generally more productive than polar, and euphotic areas are usually more species rich in the oceans.
  6. Disturbance - moderate disturbances retard competitive exclusion. For example: on rocky intertidal zones the Littorina snail is the dominant grazer. The snail feeds on the dominant algae, allowing inferior algae to survive.