Question

(a) What is competitive exclusion? What does this principle predict the outcome of two-species competitive interactions to be? (b) Besides resources, what factors directly influence the growth, survival, and reproduction of species? (c) Describe how temporal variation in the environment might influence the coexistence of competitors. (d) Under what conditions may competitive release occur? (e) Describe one mechanism that can lead to coexistence rather than competitive exclusion.

Short answer

Short Answer: Competitive exclusion predicts that two species competing for the same limited resource cannot coexist indefinitely, with one eventually outcompeting the other. Factors influencing species' growth, survival, and reproduction include abiotic and biotic factors. Temporal variation in the environment can promote coexistence by affecting species' competitive abilities differently. Competitive release occurs when a species increases in population density or range due to the removal or decline of a competitor. Mechanisms promoting coexistence rather than competitive exclusion include niche differentiation, where species partition their resource use or adapt to different aspects of their environment.

Step-by-step solution

(a) Competitive exclusion and its prediction for two-species interactions

Competitive exclusion, also known as Gause's Law, is an ecological principle stating that two species competing for the same limited resource cannot coexist in the same ecological niche indefinitely. The principle predicts that one species will eventually outcompete the other, leading to the survival of the fittest and the local extinction of the less competitive species.

(b) Factors influencing growth, survival, and reproduction of species

In addition to resources, various other factors directly impact the growth, survival, and reproduction of species. These factors can be classified into abiotic (non-living) and biotic (living) factors. Abiotic factors include temperature, light availability, precipitation, and soil chemistry. Biotic factors include predation, parasitism, disease, and mutualistic interactions with other species.

(c) Influence of temporal variation in the environment on competitors' coexistence

Temporal variation in the environment can play a role in the coexistence of competing species. When resources or environmental conditions fluctuate over time, different species may have different competitive abilities under varying circumstances. This can lead to fluctuations in population densities and a balance between the competing species, allowing them to coexist in the same ecological niche over long periods.

(d) Conditions for competitive release

Competitive release occurs when a species experiences an increase in its population density or range due to the removal or decline of a competitor. Competitive release can occur under the following conditions: (1) reduction or elimination of a competing species due to human intervention or natural factors (e.g., disease, predation), (2) significant changes in environmental conditions that favor one species over another, and (3) the absence of competition for the same resource, which allows a co-occurring species to expand into a new niche.

(e) Mechanism promoting coexistence rather than competitive exclusion

One mechanism that can facilitate coexistence between competing species rather than competitive exclusion is niche differentiation - when competing species partition their resource use or adapt to different aspects of their environment. This allows them to avoid direct competition and reduces their impact on each other's populations, allowing both species to coexist despite having some overlapping requirements for resources. Examples include spatial segregation of their habitats, different feeding habits or times, or partitioning their use of resources in the environment.

Key concepts

Understanding the Ecological Niche

An ecological niche is like a species' address and job description rolled into one. It includes the range of conditions that the species needs to survive, grow, and reproduce, such as temperature, food sources, and habitat type, along with its role in the ecosystem, like being a pollinator or a decomposer. Essentially, an ecological niche encompasses all the biotic and abiotic factors that a species requires to maintain its population.

When two species have identical niches, the competitive exclusion principle kicks in, predicting trouble. If both species need the exact same resources, they'll battle it out until one comes out on top, pushing the other out of the neighborhood. To survive alongside each other without direct competition, species can specialize, adjusting their niches to reduce overlap — this is known as niche differentiation, and it's key for coexistence.

Embracing Species Coexistence

Species coexistence is the harmonious living of multiple species within the same ecological area. It's essentially nature's way of promoting biodiversity and ensuring that no single species grocery shops itself to extinction.

A variety of factors promote coexistence, from differences in physical traits that allow species to utilize resources differently, to variations in behavior patterns, like being nocturnal versus diurnal. Even the timing of reproduction can play a role, ensuring that species don't directly compete for the same food at the same time. Moreover, the environment itself isn't static; it changes and fluctuates, contributing to what's known as temporal niche partitioning. This allows species to take turns at the ecological buffet table, reducing direct competition and enabling them to coexist more peacefully.

The Role of Biotic and Abiotic Factors

In the theater of life, biotic and abiotic factors set the stage and write the script for species interactions.

The abiotic factors, like climate, water availability, soil condition, and sunlight, are the non-living components that can dictate where a species lives and how it survives. These elements lay down the fundamental rules of survival, shaping the ecological niche and impacting species coexistence.

Meanwhile, the biotic factors — the living components, such as predators, prey, competitors, and partners — introduce the drama. They're the interactions and relationships that create a dynamic and ever-changing ecosystem. Predators can control the population of a species, competitors influence how a species uses resources, and partners like pollinators and plants can drive mutual success. When you combine these factors, you get a complex web of life where survival is a team sport, and every species plays a part in shaping the environment.