Question

In Chapter \(13,\) Figure 13.6 presents a hypothetical case where two bird species overlap in their use of food resources (seeds). Let us assume that due to interspecific competition, the two species cannot co-occur in the same habitat (say species 1 succeeds). Now assume that the distribution of seed sizes in their habitat changes from year to year depending on rainfall, and that the average seed size varies from \(a\) to \(b\) (Figure 13.19 ). How might this temporal variation in resources influence the outcome of competition between the two species?

Short answer

Answer: Temporal variation in seed sizes may affect competition between two bird species based on their preferred seed size range, adaptability to changes in seed sizes, and resource utilization. The possible outcomes include one species outcompeting the other due to better adaptability, both species sorting themselves into different microhabitats to reduce competition, or one species eventually overtaking the habitat when its preferred seed size is more abundant. Understanding each species' feeding preferences and adaptability can help determine the likely outcome of the competition.

Step-by-step solution

Define the problem scenario

We are given a hypothetical situation where two bird species, Species 1 and Species 2, cannot co-exist in the same habitat due to interspecific competition for food resources (seeds). We'll assume that Species 1 initially succeeds in this habitat. Over time, the seed sizes in this habitat vary depending on rainfall, ranging in size from `a` to `b`. We are asked to analyze the effects of this seed size variation on the competition between the two bird species.

Analyze resource preferences and competition

To determine how this variation in seed sizes might affect competition, we will need to consider the following factors: 1. What is each bird species' preferred seed size range? 2. How does each bird species adapt to changes in seed size? 3. How might these factors ultimately determine the outcome of the competition? Think about the scenario in terms of the birds' abilities to utilize a specific range of seed sizes, and how their feeding preferences and adaptability might change with the varying seed size availability.

Discuss possible outcomes

The temporal variation in seed sizes may lead to the following possible outcomes: 1. If both bird species have similar preferences and adaptability, they may continue to compete, with one species eventually overtaking the habitat when its preferred seed size is more abundant. 2. If one species is more adaptable to the range of seed sizes, it may eventually be able to exploit the food resource better and succeed in the habitat, regardless of the seed size fluctuation. This may lead to the less adaptable species being outcompeted and pushed out of the habitat. 3. If both bird species have different preferences or adaptability to a range of seed sizes, they may sort themselves into different microhabitats within the larger habitat, each utilizing a distinct range of seed sizes. This separation of resource use reduces competition and might allow both species to coexist.

Conclusions

In conclusion, the temporal variation in seed sizes from `a` to `b` might have important implications for the outcome of the competition between Species 1 and Species 2. The ability of each species to adapt to the changing resources and how well they exploit the available seed sizes will ultimately determine which bird species succeed in the habitat. Before making specific predictions for this hypothetical situation, it would be necessary to understand each species' feeding preferences and adaptability to changing seed sizes. However, the possible outcomes listed above provide starting points for further investigation and discussion.

Key concepts

Resource Partitioning

Resource partitioning is a fascinating concept in ecology that helps explain how different species coexist even though they compete for similar resources. In the case of our bird species, resource partitioning would allow them to coexist by utilizing different parts or aspects of the seed resource, possibly reducing direct competition.

Birds might partition resources through varying their feeding times, preferring different sizes of seeds, or even selecting seeds from distinct habitats or microhabitats. By dividing resources, species can reduce overlap in their ecological niches.

This kind of partitioning allows each species to thrive without directly outcompeting the other, leading to greater biodiversity and stability within the ecosystem. Some common ways species achieve resource partitioning include:

• Different dietary preferences: Selecting different sizes or types of seeds.
• Temporal shifts in activity: Feeding at different times of the day or year.
• Spatial separation: Utilizing different areas within a habitat.

Understanding resource partitioning can provide insights into how resource use patterns affect species dynamics in any given environment.

Temporal Resource Variation

Interspecific competition can be significantly influenced by temporal resource variation. This term refers to changes in resource availability over time, like the varying sizes of seeds in our hypothetical scenario. These changes can be due to natural events such as rainfall, seasons, or other environmental factors.

Temporal variation can alter which species dominate a habitat at different times. For example, if a particular seed size becomes abundant due to a rainy season, a species with a preference or adaptability to that size could gain a competitive advantage. Conversely, during other times, seeds of different sizes might proliferate, providing opportunities for another species to succeed.

This aspect of resource availability requires species to be adaptable to survive. Adaptable species tend to fare better as they can adjust their feeding habits to access the abundant resource at any given time. Thus, temporal resource variation introduces an element of unpredictability that can influence which species prevail in a competitive setting.

Ecological Niches

The concept of ecological niches plays a crucial role in understanding the dynamics of interspecific competition. An ecological niche includes all the environmental conditions, factors, and influences required for a species to survive and reproduce. Each species has its unique niche, encompassing its use of resources and interaction with other living beings.

In our scenario, each bird species would have a niche defined mainly by its seed preferences. If their niches overlap significantly, competition is high. However, if they differentiate their niches through adaptations or preference changes, they might reduce this competition.

Understanding ecological niches is essential because it shows how species interact with their environment and with each other. These interactions determine the species' ability to coexist sustainably in a shared habitat.

• Niche differences: Help reduce competition by separating how species use resources.
• Adaptive behaviors: Enable species to occupy similar habitats without outcompeting each other.

In broader ecological contexts, niches explain how biodiversity is maintained, with each species fulfilling a specific role within its ecosystem.