Ecological Niche and Habitat

An ecological niche refers to the role and position a species has in its environment. It includes all the ways a particular species interacts with and uses its habitat to survive. Some key things that define a species’ niche are:

• Food source(s): What a species eats
• Interactions: How a species interacts with other species
• Climate conditions: The temperature, rainfall, etc. a species requires

For example, Sharks occupy the niche of apex ocean predators that eat fish, squid, seals and other marine animals. So here, being an apex ocean predator is an ecological niche. Multiple species can occupy similar or even overlapping niches within the same ecosystem. For example, Killer whales Hunt and consume large prey like seals, sea lions, fish, squid.

Habitat

A habitat refers broadly to the type of natural environment in which a species lives. It includes things like geographic location and features; climate patterns; available food, water, shelter etc. Some examples habitats are as follows:

• Coral reefs – inhabited by species like clownfish, sea turtles, eels
• Deserts – inhabited by species like camels, desert tortoises
• Rainforests – inhabited by species like parrots, monkeys, frogs, insects

Is habitat part of niche?

No, habitat is not technically considered a part of a niche. However, they are closely interrelated concepts. A habitat refers to the physical environment and resources available for species to use and occupy. Things like climate conditions, vegetation, shelter, water sources, etc. make up an organism’s habitat.

A niche refers more specifically to how an organism utilizes the habitat and its resources. The niche includes the organism’s role in the food chain, life cycle interactions, nesting behaviors – essentially how it “makes a living”. The niche has more to do with how an organism fits into an ecosystem.

So while an organism’s habitat sets the stage, providing the basic needs for survival, the niche has to do with how the organism uniquely uses its habitat to survive & reproduce. Technically, Niche is not a

For example, various habitats of house sparrow include  woodlands, grasslands, and deserts; houses, factories, warehouses, zoos etc. However, when we talk about its niche, it would include – eating insects, grains, seeds etc.; making nests in houses, trees and shrubs etc. Thus, niche is a broader concept than habitat and its focus is on functional role played by the species rather than only the place it needs to live. For any organism, the niche includes both the physical habitat and how it has adapted to life in that habitat. In summary, Habitat is “address” while Niche is “profession”.

Ecological Equivalents

Organisms that occupy the same or similar ecological niches in different geographical regions are known as Ecological Equivalents. For examples, owls and cats, both feed on mice; but owls are found in deserts or forests while cats are around human habitations. In this context, owls and cats are ecological equivalents in terms of their feeding role. Similarly, Kangaroos of Australia perform the same functions (herbivores) as antelopes or Bison of North America. Both live in similar habitats of different regions but have similar profession of herbivores.

Can two species share the same niche?

In principle, two species can share an identical ecological niche, but in practice that would be highly unstable. Some key considerations on species sharing niches:

1. Niche overlap: Species can occasionally share very similar niches and resource use in a stable way, but complete niche identity is unlikely. Even similar species partition resources slightly differently or are separated geographically. This partitioning allows them to stably coexist without one outcompeting the other.
2. Competitive exclusion principle: Theory states that complete niche overlap doesn’t allow stable coexistence. In time, one species will always outcompete the other for limiting resources until it drives it to extinction or forces adoption of a slightly different niche.
3. Character displacement: Closely related competing species are under natural selection pressure to evolve to use resources differently. This causes divergence in traits over time so their niches become more distinct from each other. This allows their eventual coexistence.

Thus, transient niche sharing between similar species does occur and closely related species have high niche overlap. However, identical niches lead to competitive exclusion of one party over time. Character displacement or geographic effects then cause the evolution of differences enabling more stable coexistence. Complete identical niches are hence unlikely to be observed between two species stably coexisting in one location.

In other words, each species has one Niche; no two species can share the same niche for long because then the competition for resources will drive the inferior species out. This is called  character displacement or niche shift or niche displacement. Further, please note that competition for food, light and space is most severe between two closely related species occupying same niche.

Narrow Niche and Broad Niche

When an organism is adapted various kinds of environmental conditions for its survival, it has a generalized or broad niche. Such organisms are called generalists. On the other hand, if the organism needs specific set of conditions for its survival, it has a specialized niche or narrow niche. Such organisms are called specialists. There are many species of plants and animals which can survive only a narrow range of climatic or environmental conditions. For example, Giant Panda has a very specialized niche because 99% of its food is bamboo plants. The destruction of bamboo in China has led the Giant Panda to reach stage of near extinction. Thus, narrow niche is one of the reasons behind the extinction of species.

• Other Examples of Narrow Niche: Koalas surviving exclusively on eucalyptus leaves; Emperor penguins breeding exclusively in Antarctica; Orchids relying on a single insect for pollination
• Examples of Broad Niche: Raccoons able to live in forests, urban areas, and wetlands while eating omnivorous diets; Crows adapting well to habitats across continents; Coyotes consuming a wide variety of plants and animals.

Species with broad niches generally fare better in changing conditions. Specialist species with narrow niches are more vulnerable if their niche-specific resource declines or habitat shifts due to environmental changes.