How does competition between species affect community composition?

Competition between species significantly influences community composition by determining species abundance and diversity.

Competition is a fundamental interaction in ecological communities and plays a crucial role in shaping the structure and function of ecosystems. It occurs when two or more species vie for the same limited resource, such as food, water, light, or space. This competition can significantly affect community composition by determining which species can survive and reproduce in a particular environment, thereby influencing species abundance and diversity.

The principle of competitive exclusion, also known as Gause's Law, states that two species competing for the same limiting resource cannot coexist at constant population values. The species that utilises the resource more efficiently will eventually outcompete and exclude the other species. This principle explains why certain species dominate in specific environments and why others are less common or absent. For instance, in a forest, taller trees that can reach sunlight more efficiently will outcompete shorter plants, leading to a community dominated by tall trees.

However, competition does not always lead to the exclusion of a species. Sometimes, species can coexist through a process called resource partitioning. This is where species divide the resources among themselves to avoid direct competition. For example, different bird species may feed at different times of the day or on different parts of a tree, allowing them to coexist in the same habitat. This leads to greater species diversity within the community.

Moreover, competition can also drive evolutionary changes, a process known as character displacement. When two similar species compete, natural selection favours individuals in each species that are least like the other species in resource use. Over time, this can lead to changes in the species' traits, allowing them to utilise different resources and coexist. This can increase the diversity of species and traits within a community.

In conclusion, competition between species is a powerful force that shapes community composition. It determines which species can survive in an environment, influences species abundance and diversity, and can drive evolutionary changes. Understanding these dynamics is crucial for predicting how communities will respond to changes in resource availability due to human activities or climate change.