Ecology is the study of the interactions between organisms and their environments, which comprise an ecosystem. The places organisms live in are called habitats.
An ecological niche, in contrast, is the ecological role an organism plays within its habitat.
Ecological Niche Definition
Several branches of ecology have adopted the concept of the ecological niche.
The ecological niche describes how a species interacts within an ecosystem. The niche of a species depends on both biotic and abiotic factors, which affect the ability of a species to survive and endure.
Biotic factors affecting a species' niche include food availability and predators. Abiotic factors affecting ecological niche include temperature, landscape characteristics, soil nutrients, light and other non-living factors.
An example of an ecological niche is that of the dung beetle. The dung beetle, as its name suggests, consumes dung both in larval and adult form. Dung beetles store dung balls in burrows, and females lay eggs within them.
This allows hatched larvae immediate access to food. The dung beetle in turn influences the surrounding environment by aerating soil and rereleasing beneficial nutrients. Therefore, the dung beetle performs a unique role in its environment.
The definition of a niche has changed since it was first introduced. A field biologist named Joseph Grinnell took the basic concept of the niche and further developed it, claiming that a niche distinguished between different species that occupied the same space. In other words, only one species could have a particular niche. He was influenced by species distribution.
Types of Ecological Niches
Ecologist Charles Elton’s definition of niche focused on the role of a species, such as its trophic role. His tenets emphasized more on community similarity and less on competition.
In 1957, Zoologist G. Evelyn Hutchinson provided a sort of compromise of these trains of thought. Hutchinson described two forms of niche. The fundamental niche focused on the conditions in which a species could exist with no ecological interactions. The realized niche, in contrast, considered the population’s existence in the presence of interactions, or competition.
The adoption of the ecological niche concept has allowed ecologists to understand the roles of species in ecosystems.
Importance of Ecological Niches
Ecologists use the concept of the ecological niche to help understand how communities relate to environmental conditions, fitness, trait evolution and predator-prey interactions in communities. This becomes ever more important as climate change affects community ecology.
Ecological niches allow species to exist in their environment. Under the right conditions, the species will thrive and play a unique role. Without the ecological niches, there would be less biodiversity, and the ecosystem would not be in balance.
Interspecies competition: Ecologists refer to coexistence when describing ecological niches. Two competing species cannot exist in one ecological niche. This is due to limited resources.
Competition affects the fitness of species, and can lead to evolutionary changes. An example of interspecies competition is an animal that forages for pollen or nectar from a specific plant species, competing with other such animals.
In the case of some species of ants, the insects will compete for nests and prey as well as water and food.
Competitive exclusion principle: Ecologists use the competitive exclusion principle to help understand how species coexist. The competitive exclusion principle dictates that two species cannot exist in the same ecological niche. This is due to competition for resources in a habitat.
Early champions of the competitive exclusion principle were Joseph Grinnell, T. I. Storer, Georgy Gause and Garrett Hardin in the early and mid 20th century.
Competition in a niche either leads each species to specialize in a different way, so as not to use the same resources, or leads one of the competing species to become extinct. This is another way of looking at natural selection. There are two theories used to address competitive exclusion.
In R* Theory, multiple species cannot exist with the same resources unless they differentiate their niches. When resource density is at its lowest, those species populations most limited by the resource will be competitively excluded.
In P* Theory, consumers can exist at high density due to having shared enemies.
Competition plays out even at the microbial level. For example, if Paramecium aurelia and Paramecium caudatum are grown together, they will compete for resources. P. aurelia will eventually overtake P. caudatum and cause it to go extinct.
Overlapping Niches/Resource Partitioning
Given the fact that organisms cannot exist in a bubble and must therefore naturally interact with other species, occasionally niches can overlap. To avoid competitive exclusion, similar species can change over time to use different resources.
In other cases, they can exist in the same area but use resources at different times. This scenario is called resource partitioning.
Resource partitioning: Partitioning means separating. Simply put, species can use their resources in ways that reduce depletion. This allows the species to coexist and even evolve.
An example of resource partitioning is that of lizards like anoles, which used different parts of their overlapping habitats in different ways. Some of the anoles might live on the forest floor; others might live high in the canopy or along the trunk and branches. Still other anoles might move away from plant environments and live in deserts or near oceans.
Another example would be dolphins and seals, which eat similar species of fish. However, their home ranges differ, allowing for a partitioning of resources.
Another example would be Darwin’s finches, which specialized their beak shapes over over time in their evolution. In this way, they were able to use their resources in different ways.
Examples of Ecological Niches
Several examples of ecological niches exist in various ecosystems.
For example, in the jack pine forest of Michigan, the Kirtland’s warbler occupies an area ideally suited for the bird. The birds prefer nesting on the ground between the trees, not in them, among small undergrowth.
But the jack pine tree must be only up to eight years old and around 5 feet tall. Once the tree ages or grows taller, the Kirtland’s warbler will not thrive. These highly specialized kinds of niches can be put at great risk due to human development.
Desert plants such as succulents adapted to arid ecological niches by storing water in their leaves and growing long roots. Unlike most plants, succulents open up their stomata only at night so as to reduce water loss from scorching daytime heat.
Thermophiles are organisms that thrive in extreme ecological niches such as thermal vents with high temperatures.
Channel Islands Ecosystem
In Southern California, mere miles away from one of the most populous areas of human settlement in the United States, the chain of islands known as the Channel Islands provides a fascinating ecosystem for studying ecological niches.
Nicknamed the “Galapagos of North America,” this delicate ecosystem plays host to numerous plants and animals. The islands vary in size and shape, and they provide unique habitats for various animals and plants.
Birds: Several birds call the Channel Islands home, and despite their overlap they have each managed to occupy special ecological niches on the islands. For example, the California brown pelican nests on Anacapa Island by the thousands. The island scrub jay is unique to the Channel Islands.
Fish: Over 2,000 fish species live in the waters around these islands. The kelp beds under the ocean provide habitat for both fish and mammals.
The Channel Islands have suffered from the introduction of invasive species by European settlers, as well as from pollutants such as DDT. Bald eagles disappeared, and taking their place, golden eagles made a home. However, bald eagles have been reintroduced to the islands. Peregrine falcons underwent a similar crisis and are making a comeback.
Native mammals: Four native mammals reside in the Channel Islands: the island fox, harvest mouse, island deer mouse and spotted skunk. The fox and the deer mouse in turn have subspecies on separate islands; each island therefore hosts separate niches.
The island spotted skunk prefers habitat of different types depending on the island it lives on. On Santa Rosa Island, the skunk favors canyons, riparian areas and open woodlands. In contrast, on Santa Cruz Island, spotted skunks prefer open grassland mixed with chaparral. They play the role of predator on both islands.
The island spotted skunk and the island fox are competitors for resources on the islands. However, the spotted skunks are more carnivorous, and they are nocturnal. So in this manner, they are able to coexist in overlapping niches. This is another example of resource partitioning.
The island fox nearly went extinct. Recovery efforts have brought the species back.
Reptiles and Amphibians: The highly specialized niches extend to reptiles and amphibians. There is one salamander species, one frog species, two non-venomous snake species and four lizard species. And yet they are not found on every island. For example, only three islands play host to the island night lizard.
Bats also occupy niches on the islands of Santa Cruz and Santa Rosa, working as both pollinators and consumers of insects. Santa Cruz Island is a home for Townsend’s big-eared bats.
Today the islands are recovering. They now comprise Channel Islands National Park and the Channel Islands National Marine Sanctuary, and ecologists continue to monitor the many creatures that call the islands home.
Niche Construction Theory
Ecologists more recently have focused on niche construction theory, which describes how organisms modify their environments to make them better suited as niches. Examples of this include making burrows, building nests, creating shade, building beaver dams and other methods in which organisms alter their surroundings to suit their needs.
Niche construction arose from biologist John Odling-Smee. Odling-Smee argued that niche construction should be considered a process of evolution, a form of “ecological inheritance” passed on to descendents rather than a genetic inheritance.
There are four core principles behind niche construction theory:
- One involves non-random modification of the environment by a species, helping aid their evolution.
- Second, the “ecological” inheritance alters evolution due to parents passing on the altering skills to their offspring.
- Third, new characteristics that are adopted become evolutionarily significant. The environments are affected systematically.
- Fourth, what was considered adaptation is essentially the result of organisms making their environments more complementary via niche construction.
An example would be a seabird’s feces that lead to plant fertilization and a transition from scrubland to grassland. This is not an intentional adaptation, but it has brought implications for evolution. The seabird would therefore have significantly modified the environment.
Other modifications to the environment must affect the selection pressures on an organism. The selective feedback is unrelated to genes.
Examples of Niche Construction
More examples of niche construction include nesting and burrowing animals, yeast that modify themselves to attract more fruit flies and the modification of shells by hermit crabs. Even by moving around, organisms can affect the environment, in turn influencing gene flow in a population.
This is seen on a grand scale with humans, who have so altered the environment to suit their needs that it has led to worldwide consequences. This certainly can be evidenced by the transition from hunter-gatherers to agrarian cultures, which altered the landscape in order to raise food sources. In turn, humans altered animals for domestication.
Ecological niches offer rich potential knowledge for understanding how species interact with environmental variables. Ecologists can use this information to learn more about how to manage species and to conserve them, and how to plan for future development as well.
About the Author
J. Dianne Dotson is a science writer with a degree in zoology/ecology and evolutionary biology. She spent nine years working in laboratory and clinical research. A lifelong writer, Dianne is also a content manager and science fiction and fantasy novelist. Dianne features science as well as writing topics on her website, jdiannedotson.com.