Question

B. Keystone species are species that have a very large impact on community structure and the food web if removed from the system. For example, the presence or absence of large herbivores can have an impact on snake abundance in African grasslands. McCauley & Young performed experiments in Kenya (1997-2006) where fences were constructed around plots to exclude elephants and zebras. After 8 years, snakes were counted; the results are shown in the accompanying graph. Please offer an explanation of how removing large herbivores caused snakes to increase. erbivores herbivores

Answer 1

As already mentioned in the query, keystone species play a very important role in the ecosystem. They are the species that provide a definition to a particular ecosystem and on their removal, their ecological niche cannot be fulfilled by other species. They form a pivotal point in food web.

There can be a vatovar of charactrristic that makes a particular sirvies in a particular ecosystem the keysykey species. In the exoedienbt performed by Young and McCauley, where larger herbivores like elephants and zebras were stopped from entering fenced plots and these plots showed increase in snake population. Now in this particular ecosystem i.e. ; the African grasslands, elephants and larger herbivores are keystone species. On their removal, the competition(because rodents and elephants feed on the same-grasses, shrubs etc) between them and smaller herbivores like rodents has been practically erased leading to a higher growth in the population of rodents. This in turn has lead to the increase in population of predators of these rodents - snakes.

Therefore snake population has increased as their prey population (rodebts and other smaller herbivores) has well increased.