1. Community interactions: the niche concept and symbiotic relationships

2. HABITATS ARE DEFINED AND CONSTANT
Any species has a well defined habitat
‘its address’
Where it can live
What it needs to eat
Breeding grounds
Water requirements
etc etc
HABITATS ARE DEFINED AND CONSTANT
Any population of that species has a well defined niche
‘its occupation’
The species it interacts with
The species it depends on
The species that depend on it…
NICHES CAN GROW AND SHRINK, DEPENDING ON ‘EXTERNAL’ FACTORS

3. Habitat The area where an organism lives is called its habitat.
A habitat includes both biotic and abiotic factors

4. ‘Nicher’ (French): to Nest
A term describing the way of life of a population
No two species can occupy the same niche in the same ecosystem
To describe a population’s niche, you need to describe its ‘specialised habitat’:
space and territory
Nutrition and feeding habits
Interactions with other organisms
Its reproductive habits
Its role in the community

5. The Niche concept: A Working Analogy
In 1927, Charles Sutherland Elton, the British Ecologist, stated: ‘When an ecologist states ‘There goes a badger’, he should include in his thoughts a definite idea of the animal’s role in the community, just as if he had said ‘There goes the vicar’

6. Defining a Niche : ‘The Boundary conditions’
Two species that use exactly the same resources cannot occupy the same niche
Only one species or population can occupy the same niche for an extended period

7. A population has a fundamental AND a realised niche

8. Fundamental Niche
A species’ fundamental niche is the full range of environmental and social conditions under which it could potentially survive and reproduce
‘potential niche’
Some species have a broad fundamental niche
Some species have a narrow fundamental niche

9. Species with a broad niche
‘Generalists’
Widely distributed geographically
Adaptable

10. Species with a narrow Niche
‘Specialists’
Not adaptable
Under threat of extinction if the niche changes

11. Realised Niche
The realised niche is the specific set of conditions in which it survives in a given habitat or ecosystem, given the other species or limitations present. These are the conditions to which the population is best adapted.

12. ‘Realised Niche’ is not a constant for a species
In fact, populations of the same species may occupy different realised niches within different ecosystems
It all depends on the other species and environmental factors involved in ‘sharing of the resources’

14. What interactions occur within communities?

15. All community interactions play an essential role in survival of both species

16. Essential Interactions
Predation Parasitism Mutualism (Commensalism) Competition

17. Symbiosis
Any ‘long term’ relationship in which two species live closely together is called symbiosis.
Symbiotic relationships include:
mutualism
commensalism
parasitism
(predation)

18. ‘Symbiotic’ relationship 1: Predation

19. Predation
An interaction in which one organism captures and feeds on another organism is called predation.
The organism that does the killing and eating is called the predator, and the food organism is the prey.

20. Parasitism: one organism (the parasite) lives on or inside another organism (the host) and harms it.
yuk.....!
The parasite of the day Blog...

21. Community Interactions
Mutualism: both species benefit from the relationship. Commensalism: one member of the association benefits and the other is neither helped nor harmed.

22. Symbiotic relationships can take place between species from different kingdoms!
Symbiosis
Mutualism, Commensalism and parasitism
Sunfish and seagulls...
Fish Cleaners
Giving Fish a bath
Clownfish and anemones

23. Competition
Competition occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time.
A resource is any necessity of life, such as water, nutrients, light, food, or space.
Direct competition in nature often results in a winner and a loser—with the losing organism failing to survive.

24. The principle of competitive exclusion
Aka ‘Gause’s Law’
‘No two species can occupy the same niche in the same habitat for a prolonged time’

25. The Competitive Exclusion Principle
The best adapted species will survive
The loser will struggle to survive and reproduce, and will eventually become extinct OR migrate (if its niche is broad enough)
Examples are abundant
Invasive species
Red versus Grey Squirrel in Western Europe
Gause’s Paramecium

27. Competitive Exclusion and Invasive species…
Invasive Species are those which have been introduced to a non-native habitat/ecosystem (usually by human interention). They often out-compete – (and drive towards extinction) – the native species…
Grey Squirrels
Cane toads!
Zebra Mussels

28. Competitive Exclusion: Squirrels

29. Competitive Exclusion: Squirrel Distribution

30. Competition in the plant world
Japanese knotweed
David Attenborough tropical conpetition

31. Competition can even take place between species from different kingdoms…
Spider versus plant

32. Can species ‘work around’ the competitive exclusion principle?

33. Yes they can!: Niche Partitioning
As there is a limited about of space and resources on Earth, organisms can use niche partitioning 1. Spatial: Two different species use the same resource by occupying different areas within the range of the resource 2. Temporal: Two species eliminate direct competition by using the same resource at different times

34. Spatial Niche Partitioning
Closely related bird species occupy different foraging locations on a single tree species

35. Community Interactions
The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree. 18 12
Feeding height (m)
Cape May Warbler
Each of these warbler species has a different niche in its spruce tree habitat. By feeding in different areas of the tree, the birds avoid competing with one another for food.
Bay-Breasted Warbler 6
Yellow-Rumped Warbler

36. Temporal Niche Partitioning
Different species of spiny mouse inhabiting the same ecosystem may be either nocturnal OR diurnal feeders