8.1: A summary of Interactions
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Introduction to Communities
Populations rarely, if ever, live in isolation from populations of other species. All populations occupying the same habitat form a community (populations of multiple species inhabiting a specific area at the same time). The number of species occupying the same habitat and their relative abundance is known as species diversity. Areas with low diversity, such as the glaciers of Antarctica, still contain a wide variety of living things, and those living things interact with one another. In ecology, a biological interaction is the effect that a pair of organisms living together in a community have on each other. Interactions may involve direct contact such as a predator consuming its prey, or indirect such as two bird species competing for the same seeds to eat. Such interactions among different species play a major role in regulating population growth and abundance. Ecology is studied at the community level to understand how species interact with each other and compete for the same resources.
In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time. Ecologists investigate the factors that influence biodiversity, community structure, and the distribution and abundance of species. These factors include interactions with the abiotic world and the diverse array of interactions that occur between species.
A species interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species (intraspecific interactions), or of different species (interspecific interactions). Interactions between organisms can result in positive (+), negative (-), or neutral (0) outcomes; in ecology the pairwise combinations of these are defined as:
- competition (-/-)
- predation (+/-)
- mutualism (+/+)
- commensalism (+/0)
- amensalism (-/0)
- neutralism (0/0)
All of these interactions can be organized by the effects the species have on each other (Figure \(\PageIndex{1}\)).
Species interactions may be short-term, like pollination and predation, or long-term; both often strongly influence the evolution of the species involved. Short-term interactions are short-lived in terms of the duration of a single interaction: a predator kills and eats a prey; a pollinator transfers pollen from one flower to another; but they are extremely durable in terms of their influence on the evolution of both partners. As a result, the partners coevolve.
Competition can be defined as an interaction with negative effects on both species that require the same limited resource to survive, grow, and reproduce. Competition, is generally divided into intraspecific competition, competition between individuals of the same species, and interspecific competition, competition between individuals of different species. Competition can take the form of interference competition, involving direct interactions between individuals; or resource competition, in which individuals compete through their dependence on the same limiting resources.
We have already explored the affects of intraspecific competition in the form of logistic population growth. Competition between members of the same species for recourses in the environment affects the growth rate (r) of the population, and generally limits the population to its carrying capacity (K).
Watch this video to know the difference between interspecific and intraspecific, and that interactions can be positive, negative or neutral. Interspecific interactions are between different species. Intraspecific interactions are between members of the same species. Positive interactions benefit everyone involved, negative interactions are to the detriment of one species, and neutral interactions neither benefit or negatively impact the individual.
Two male tule elk are competing with each other to mate with females in the herd. Is this interaction interspecific or intraspecific?
- Answer
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Intraspecific because it is occurring between individuals of the same species.
The diversity of interactions between herbivores and plants, between predators and prey, and between parasites, parasitoids, pathogens, and hosts can be grouped under the heading of exploitative interactions—interactions between species that enhance the fitness of one individual at the expense of another. These interactions are also known as enemy-victim interactions because one organism (the enemy) is the consumer of another (the victim), In exploitative interactions, the enemy and victim often coevolve with each other.
Mutualism, interactions between individuals that benefit both partners, is a common phenomenon in nature that has apparently made important contributions to the evolutionary history of life and continues to make key contributions to the ecological integrity of the biosphere. Mutualisms can be divided into those that are facultative, where species can live without their mutualistic partners, and obligate, where species are so dependent on the mutualistic relationship that they cannot live without their mutualistic partners.
Attribution
This Page is a modified derivative of:
- Chapter 14: Introduction to Species Interactions; CC BY-NC-SA
- 45.6: Community Ecology by OpenStax, is licensed CC BY