Community Ecology

1. Community Ecology Studying the interactions between species • interactions between coexisting population • Understanding the many spatial and temporal scales of an ecostystem, including the distribution, structure, abundance, demography: habitat and the niche concept

2. Understanding – and predicting - community interactions is difficult

3. Big questions in Community ecology Why do symbiotic relationships exist? What would be the motivation? Are human behavioural motivations different from that of other mammals? Is it human nature to be co-operative or adversarial (or co-operversarial?)

4. What interactions occur within communities?

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

6. Symbiosis Any ‘long term’ relationship in which two species live closely together is called symbiosis. You should be able to recognise: • predation • mutualism • commensalism • parasitism • competition

7. 1. 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.

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

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

10. 2. Predation

11. 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 the predator, and the food organism is the prey. Monk Seals

12. 3. Parasitism • yuk.....! • The parasite of the day Blog... • One organism lives on or inside another organism and harms it. • The parasite benefits in terms of energy or nutrients, whereas its host is harmed by the loss of these reserves • Parasites often have more limited metabolism so cannot survive out of contact with a host

13. 4. Commensalism/mutualism Mutualism: both species benefit from an interdependent relationship. Commensalism: one member of the association benefits and the other is neither helped nor harmed. Examples: mitochondria and chloroplasts; nitrifying bacteria and legume root nodules

14. 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

15. Community Ecology Organising ecosystems

16. Biotic and Abiotic Factors Ecosystems are influenced by a combination of biological and physical factors. Biological factors – these are called Biotic factors ‘The whole cast of characters with which an organism interacts’ – e.g. plants, trees, predators, competing organisms’…

17. Biotic and Abiotic Factors Physical, or nonliving factors that shape ecosystems are called Abiotic factors. Abiotic factors include: • temperature • precipitation • humidity • wind • nutrient availability • soil type • sunlight

18. How do biotic and abiotic factors influence an ecosystem? Biotic and abiotic factors determine the types of organisms which can inhabit any particular ecosystem How do biotic and abiotic factors influence an ecosystem?

19. 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 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

20. Biotic and Abiotic Factors The area where an organism lives is called its habitat. A habitat includes both biotic and abiotic factors.

21. The Niche A nicheis the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. No two species can share the same niche in the same habitat

22. ‘Nicher’ (French): to Nest A term describing the way of life of a population 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

23. 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’

24. 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

25. A population has a fundamental AND a realised niche

26. 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

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

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

29. 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.

30. ‘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’

32. 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’

33. 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

35. 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

36. Competitive Exclusion: Squirrels

37. Competitive Exclusion: Squirrel Distribution

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

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

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

41. 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

42. Community Interactions The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree. 18 12 Cape May Warbler Feeding height (m) Bay-Breasted Warbler 6 Yellow-Rumped Warbler 0

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

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